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Phosphate fertiliser prices are once again extreme. This effects super phosphate, single super, triple super, MAP, DAP, MKP, etc pricing and availability. Supply and demand determines prices but these increases are mainly on the supply side. The war in Ukraine has caused sanctions on Russia further limiting the number of suppliers in the world market. Morocco basically controls the world price as the world has under invested for decades in developing phosphate mines.

The ABC just did a video below but I have a few issues with the reporting.

1/ Australian soils have large reserves of phosphate but they are often in plant unavailable forms.

2/ Using tax player funding to build infrastructure isn’t moral or wise as the price will correct at some stage and we are a high cost producer.

3/ Rock phosphate may never become plant available. You need extensive microbial activity (labile carbon and moisture) and/or low soil pH to release the phosphate. Applying to dead soil is a total waste of resources/capital.

A more sustainable solution that requires no tax payer funding is mycorrhizal fungi as that can help unlock existing phosphate reserves. Even better than mycorrhizal fungi is implementing a cover crop strategy if possible.

Mycorrhizae are tiny, beneficial organisms that live in the soil and connect to plant roots, providing them with moisture and nutrients. The tiny fibers are called hyphae.

Living Soil is very important to plant care. It is no surprise then that nursery professionals continue to increase their understanding of it.

Living soil includes a myriad of soil-dwelling organisms, including bacteria, fungi, soil arthropods, and a wide variety of others. One of the most intensive studies groups in recent years also has the most potential for use by nursery professionals; mycorrhizal fungi.

My-Co-Rise-ee

There is a special relationship that exists between plant roots and certain types of fungi. Which are called mycorrhizae. The name is pronounced by my-co-rise-ee. Its literal meaning is “Fungus Roots”(“myco” meaning fungus “rhiza” meaning root).

These fungi are a major component of a multitude of hardworking armies of beneficial soil organisms largely invisible to us beneath the soil surface.

The mycorrhizal relationship is a symbiotic relationship. Both the plant and the fungus benefit. Nearly all horticulturally important plants and approximately 90 percent of all higher plants depend on the mycorrhizal relationships in their natural habitats.

MYCORRHIZAE

These hard-working fungi provide the cornerstone for sustainability of our plant communities. They provide the moisture and nutrients needed to keep plants in our natural areas healthy and functioning through tiny absorptive threads called hyphae.

We could not survive a day without them. Without their diligent munching in the soil, plants in native ecosystems all over the world would go hungry and die of thirst.

Ancient workers

Since the early days, 460 million years ago, these mycorrhizal fungi have been amazingly prolific. Miles of fungal filaments can explore a single thimbleful of healthy soil. They pluck phosphorus, nitrogen and micronutrients out of the soil with a specific arsenal of designer enzymes just right for the job.

Mycorrhizal fungi process waste and make it usable again, purify our water, and keep our plant communities productive. The wide variety of nursery plants will thrive when given the right source of mycorrhizal inoculum in areas where it has been lost to disturbance or not present in sterile soil mixes.

Mycorrhizal fungi attach themselves to the roots of plants and radiate out into the soil, helping their host plants absorb water and nutrients. In return, the host tree feeds the fungi with sugars, proteins, amino acids and other organic substances.

Fungi are made up of filaments called hyphae. A mass of hyphae is a mycelium, which can grow very rapidly. A fungus colony can produce more than a kilometer of new mycelium in 24 hours!

This growth form has a very high surface area. This is one of the attributes that makes the symbiotic relationship so successful. Mycorrhizae can spread their net of hyphae far and wide in the soil, penetrating tiny spaces in the soil where plant roots can’t go.

In addition, fungi are also capable of breaking down, or converting, some nutrients such as nitrogen and phosphorus to forms usable by plants.

The good news and the bad news

The good news is when water and soluble nutrients are amply provided, non-mycorrhizal plants can grow well under nursery conditions. However, until they form mycorrhizae, they don’t efficiently take up water and nutrients at the nursery or upon being planted in the ground.

Routine nursery practices such as fumigation, sterile soilless growing media and chemical use produce non-mycorrhizal plants. The bad news is that target plants do not utilize much of the fertilizer used in the nursery industry because the root/mycorrhizal system is underdeveloped.

In addition, many nursery-grown plants (and their roots) are adapted to nursery conditions and not to the highly disturbed and sometimes hostile environment found in many urban and suburban settings. In these settings, the chance of a beneficial mycorrhizal fungus colonizing the roots can be low because there may be no source of inoculum readily available.

To confirm the effectiveness and benefits of mycorrhizal treatment, I conducted a test of a mycorrhizal inoculant for four important horticultural species at Village Nursery in Sacramento, Calif.

My hypothesis was that mycorrhizal fungi could be established under nursery conditions and would increase the plants’ root system capacity to effectively uptake nutrients at levels considered by conventional standards to be lower than optimum rates. I wanted to test whether inoculated plants’ growth and development would be adversely affected as a result of reduced fertilizer inputs.

The experiment

Four plant families were tested because of their popularity in the landscape industry: 1) Cotoneaster apiculata, 2) Trachelospermum jasminiodes, 3) Pinosponim uariegate, and 4) Escallonia fradesii. The experiment had three fertilizer treatments. 

1) Grower standard practice (GSP). For this control group, I applied 8 pounds Apex 23-6-12 per cubic yard (equivalent to 0.23 pounds nitrogen per cubic yard over an 8 month period). Because this was the control group, there was no mycorrhizal inoculation.

2) Apex mixed at 20 percent less than GSP. I added a fertilizer ratio of 6.5 pounds Apex 23-6-12 per cubic yard (equivalent to 0.19 pounds nitrogen per cubic yard over an 8 month period) with mycorrhizal inoculation.

3) Apex mixed at 30 percent less than GSP. I fertilized with 5.5 pounds 23-6-12 per cubic yard (equivalent to 0.15 pounds nitrogen per cubic yard over an 8 month period) with mycorrhizal inoculation.

How the experiment was conducted

For each plant species and fertilizer/mycorrhizal treatment there were 50 replications. Mycorrhizal inoculum was watered in (drenched), until water began dripping from the bottom of the 2-inch liner pots. Mycorrhizal inoculum was used at a rate of 1 pound per 200 gallons of water. Each pound treated approximately 2,000 square feet of nursery plants.

The standard fertilization (GSP) rate was not inoculated. The plots with Apex mixed at 20 percent below standard and 30 percent below standard were inoculated with Mycorrhizal inoculum. For all treatments, lime was added to the soil at the standard 7 pounds per cubic yard of soil. A premix containing other nutrients was added. It included 1 pound Nitroform fertilizer, 1 pound FeSO4 (iron sulfate) , 0.75 pounds Tiger-90 sulfur fertilizer, and 1 pound triple phosphate (fertilizing supplemental blend) per cubic yard.

All plants were allowed to continue growing for 90 days. At the end of 90 days, root systems were sampled, cleared, and stained to determine the presence of mycorrhizal colonization of the plant root systems. Afterward, plants were transplanted as 2-inch liner pots into 1-gallon containers. Plants were set up aside the GSP in the grow grounds under the typical Rain Bird irrigation system. These plants were monitored for visual differences in growth and development. Random subsamples of Rscallonia Weir were selected for biomass measurements.

Results

Mycorrhizal colonization averaged 48 percent and 56 percent for the Mycorrhizal inoculum treatments with fertilization reductions of 20 percent and 30 percent. In the untreated, or control plants, there was only 3 percent mycorrhizal root colonization. No significant visual differences were detected in plant growth development between standard growing practices and 20 and 30 percent reduction in fertilizer with Mycorrhizal inoculation. In fact, in nearly all cases, plants are grown with fertilizer reduction treatments with mycorrhizal inoculation looked as good or better than the GSP.

A subsampling of Rscallonia species biomass indicated that the plants treated with 20 percent less fertilizer had 15 percent greater biomass than plants receiving the GSP treatment.

Conclusions

Mycorrhizal inoculants are not a silver bullet but are another valuable tool available to the nursery professional. Mycorrhizal colonization was achieved by a simple inoculum drenching of the plant material. In this experiment, a significant reduction of fertilizer inputs accompanied by mycorrhizal inoculation of a plant’s root system achieved a high level of mycorrhizal colonization. The plants that received mycorrhizal inoculations and were treated with 20 percent or 30 percent less fertilizer than standard practice did not suffer adverse plant growth or development.

Establishing nursery plants on disturbed sites requires an understanding of the many soil processes important in facilitating uptake, storage, and cycling of nutrients and water. In natural areas, these activities are largely performed by a diversity of beneficial soil organisms. These include mycorrhizal fungi working hard below the living soil surface.

In past decades, clearing of natural areas, compaction, and disturbances in suburban and urban environments have substantially reduced mycorrhizal populations. Reestablishing these beneficial fungi can occur at the nursery.

The result can be substantial fertilizer savings without adversely affecting plant growth and development. The resulting will have root and mycorrhizal systems that are well suited for the out-planted environment.

It’s as easy as A-B-Seeds

 

It might be a revelation to most people that plants in their natural environments do not have roots. Strictly speaking, they have mycorrhizae. Yes, 90 percent of the world’s plant species form mycorrhizae in their native habitats. This “symbiotic” or mutually beneficial relationship is nothing new. Mycorrhizal fungi have coevolved with plants and soils for over 460 million years. The bottom line is that the mycorrhizal relationship is as common to the roots of plants as chloroplasts are to the leaves of plants. Plants use leaves to fulfill their carbon needs and mycorrhizal fungi to attain nutrients and water. Why is this important to farmers? Cropping systems could be more sustainable with the management of mycorrhizal fungi for increased yields and less reliance on agrochemicals.

In previous Acres U.S.A. articles, we have learned about the fungal-plant symbiosis in some detail, become aware of the numerous and valuable benefits afforded crop plants by the mycorrhizal association, and explored how to determine whether or not the fungi are present in pastures or croplands. Now we will focus on the A-B-“Seeds” of inoculating with mycorrhizae. Specifically, we will explore methods and management that will restore, maintain and enhance mycorrhizal activity on the farm.

Literally, thousands of research papers have been written on mycorrhizal fungi, and farmers are becoming well-versed on the benefits. Numerous brands of commercial mycorrhizal inoculums are available but, unfortunately, some have been marketed as a “silver bullet” that will cure all your farm problems. For experienced farmers who already know how to grow crops, we’d like to share with you how to grow them even better.

Mycorrhizal fungi are keystone species anchoring a truly healthy soil that contains a prodigious abundance of biological activity. One heaping tablespoon of healthy soil may contain billions of soil organisms. Just an ounce can contain numbers of organisms equal to the earth’s entire human population! An acre of healthy topsoil can contain a web of life that includes 900 lb of earthworms, 2,500 lb of fungi, 1,500 lb of bacteria, 130 lb of protozoa, 900 lb of arthropods and algae, and in most cases, even some small mammals. This plethora of soil organisms equates to billions of miniature bags of fertility, each storing nutrients in its body tissue while slowly converting them into plant-available forms.

“A” quick background

Just to review, “myco” means “fungus” and “rhizae” means “root,” and so the word “mycorrhizae” means “fungus roots.” In these mutually beneficial partnerships, the root of the host plant provides a convenient substrate for this free “room-and-board,” the mycorrhizal fungus provides several benefits to the host plant.

A mycorrhiza (the plural is mycorrhizae) is an anatomical structure that results from a symbiotic association between soil fungi and plant roots. In exchange for a “home,” the fungus provides numerous benefits to the host plant. Mycorrhizal fungi produce an extensive network of microscopic hyphal threads that extend into the surrounding soil or growing medium. The group of mycorrhizal fungi that are most important to agriculture is called arbuscular mycorrhizal fungi (AMF or sometimes endomycorrhizal fungi). These fungi are found on the vast majority of agricultural plants with the exception of canola, the cabbage family, spinach, and sugar beets. AMF also forms mycorrhizae with a wide variety of wild and cultivated plants including most grasses, tropical plants, and most fruit and nut trees.

Commercial Mycorrhizal

Inoculants If you have determined that your crop or pasture roots are well colonized with mycorrhizal fungi, congratulations! You may skip ahead in this article to the section that reviews methods that help maintain or enhance mycorrhizal activity and populations. However, if your land has been repeatedly tilled or left fallow or if root colonization analysis of your crop or pasture plants indicates low levels or absence of mycorrhizal colonization, you will find re-establishing and rebuilding effective populations can be relatively easy and cost-effective (see Figure 2).

The fastest, most effective way to restore depleted mycorrhizal populations in croplands or pastures is to apply a commercial mycorrhizal inoculant to the roots or seeds. The technology in commercial inoculants has advanced tremendously in recent years. Many inoculants are viable for up to two years or more, remain tolerant of temperatures from well below freezing up to 140°F, and are compatible with most fertilizers and pesticides. Modern inoculants are available in diverse forms such as granular, powder, and liquids to accommodate a variety of equipment and application methods.

“B” with Seed

Benefits are maximized when the mycorrhizal fungus colonizes the roots as early in the plant’s life as possible. In a perfect world, this is immediately after the seed has germinated and begun to sprout. The active components in the inoculum are mycorrhizal fungi propagules in the form of spores and colonized root fragments (see Figure 3). When one of these colonizing units touches or comes into very close proximity of living root tissue — in this case the sprouted seed, they are activated by minute amounts of specialized root exudates and begin the mycorrhizal colonization process.

Within a brief period ranging from a few days to a few weeks, the newly colonized root cells begin to send hyphal threads from the young plant’s roots. The hyphae then begin absorbing moisture and nutrients from the surrounding soil. These processes result in greatly improved chances for survival compared to non-mycorrhizal plants. Almost immediately, the colonized sprout develops special “tools” to secure adequate moisture, and nutrients. The hyphae quickly grow and spread throughout the surrounding soil, penetrating the tiny spaces between soil particles (see Figure 4). As they encounter more roots, these also become colonized. Then, each of these roots produces more hyphae which, in turn, colonize even more roots until a massive hyphal network has pervaded the expanded rhizosphere. Clearly, inoculating seeds with mycorrhizae is an effective way to go. The benefits are the greatest and the cost is minimal, since treating a seed usually takes less inoculum than is required to colonize the larger root system of a more developed plant.

Seed treatment is best accomplished using either powdered or liquid mycorrhizal inoculants applied so that the inoculum adheres directly to the surface of the seed. Powdered inoculants work well with hairy-textured seeds such as wheat, barley, oats, or any grass seeds. Seed adhesion is important not only to ensure inoculum proximity to the germinating seed but because excess powder falling off the seeds can accumulate in the seedbox, possibly leading to mechanical problems with the auger and drill operation of the planting equipment.

A liquid inoculum is often preferred for corn, beans, alfalfa, and similar smooth-surfaced seeds because it will adhere well. A “sticker” or tackifier product is necessary to apply powdered inoculants to these types of seeds to keep the powder attached to the seed surface. Inoculum application can also be accomplished using specialized seed-treating equipment, a service often provided by seed or agronomy suppliers. Alternatively, many growers treat their seed on the farm using cement mixers or by lightly spraying liquid inoculum on the seed as it passes on the conveyor to the seedbox on the planter. If done carefully, simply stirring in a powdered inoculant as the seed is placed in the seedbox and allowing the augers to further distribute the inoculant onto the seed will suffice. Often a liquid inoculum can be applied to the seed by mixing it with other seed treatments such as legume inoculants on beans, alfalfa, and vetch.

The near-seed experience

If one or more factors such as equipment limitations, excessive seed handling, physical seed properties, etc. preclude the seed application methods suggested above, there are yet other viable methods available to place the mycorrhizal inoculum on or near the seed. A liquid mycorrhizal inoculum can be sprayed in-furrow alone or with other liquids. In some cases, a granular inoculum can simply be mixed with the seed in the furrow. Another method involves shanking or banding a granular inoculum a few inches below and/or to the side of the furrow. While this latter technique does not inoculate the seed immediately upon germination, the young plants become colonized as their roots enter the treated bands. This latter method often dovetails well with fertilizer or other planting process applications.

Getting to the roots

Establishing root colonization using commercial mycorrhizal inoculants is not limited to seed treatment or to the crop planting process. Plants may also be treated after planting, including established crops and pastures. In these situations, the method employed is to shank or knife in a granular inoculant in the soil adjacent to the growing crop. In this situation, the roots become colonized when they eventually enter the treated soil. This kind of application is not uncommon among vegetable row crops grown from young transplants. Treating established crops is particularly worthwhile with perennial crops such as alfalfa in which a one-time inoculation will continue to deliver benefits over several years. The amount of inoculant used to treat such a crop is greater (and therefore also the cost) but the advantages apply to multiple harvests. Forage pastures are another excellent example whereby either a one-time or a few incremental applications can afford very long-term benefits.

Yet another way to restore mycorrhizal colonization to perennial or permanent grass crops such as hayfields or pastures is to simply use inoculant-treated seed when over-seeding. The treated seed will quickly colonize and spread the fungi to surrounding roots. After a few over-seeding repetitions, the cumulative effects will have thoroughly colonized the field.

“C”hoosing an AM Inoculant

Base your choice of mycorrhizal inoculant on the crop plant(s), the application method (e.g. seed, furrow, etc.), available equipment, and other application considerations such as labor. Let the ease of application be your guide when choosing a product. Look for products with long shelf life, good propagule counts, and some diversity of AM mycorrhizal fungal species. Although single-species inoculants can be used (Glomus intraradices is the most commonly used), results are often enhanced by the inclusion of multiple species (see Figure 5a and 5b). Application rates may vary depending on the concentration of propagules in an inoculum and, of course, the crop, seed, or plant spacing and other factors. Essentially, application rates are based upon placing sufficient numbers of spores on or near seeds or roots to ensure fast and effective colonization throughout the crop.

Minding your “p’s”

When applying a mycorrhizal inoculant at planting, it is important to avoid high levels of available phosphorus in the soil proximate to the target seed or roots. Readily available soil phosphorus in excess of approximately 70 ppm can prevent the mycorrhizal spores in an inoculant from breaking dormancy when in near contact with a live root. Since one of the primary natural functions of the mycorrhizal relationship is to access and mobilize phosphorus, the spores have been “programmed” to delay activation in an abundant phosphorus environment. The propagules are not harmed and do not expire under such circumstances, however, they remain dormant and colonization does not commence until the ambient phosphorus levels diminish. Insoluble forms of phosphorus, such as phosphates of aluminum, iron, calcium, or magnesium which may naturally occur in soils do not contribute to this phenomenon. Likewise, phosphorus from organic or natural fertilizers such as soft rock phosphate, manures, humates, fish fertilizers, or kelp is not problematic. It is readily available phosphorus, derived primarily from soluble (liquid) or fast-release fertilizers that contribute to this situation. The solution is to avoid high rates of P starter fertilizers. Remember that one of the primary reasons for high P in starter fertilizers is to overcompensate for the inefficiency of non-mycorrhizal roots. Once crop plants become colonized with mycorrhizal fungi, these high P levels are no longer required. Phosphorus fertilizers applied anytime 10 to 20 days after inoculation and colonization have occurred need not be restricted. Note, however, due to the greatly improved phosphorus uptake efficiency imparted by the mycorrhizal association, amounts of P fertilizers needed for good crop performance may be noticeably reduced.

Mycorrhizae Maintenance

Once you have re-established mycorrhizae on your crops, there’s not much that will remove them from the living roots, but there are a lot of things that will help them colonize quicker, more thoroughly, and increase the density of the hyphal network. What do compost, compost teas, no-till methods, humates, seaweed extracts, and fish fertilizers have in common? All of them, in diverse and various ways, increase the microbial activities in soils, including the mycorrhizal fungi which then spread from root to root faster and further enhance the nutrient uptake efficiency of the colonized plants.

A, B, Seeds

Scientific research confirms that fallow, frequent tilling, erosion, compaction, and high levels of soil phosphorus availability delay, reduce or eliminate the soil’s mycorrhizal fungal populations. Advancements in our understanding of mycorrhizal fungi and their requirements have led to the production of concentrated, high-quality mycorrhizal inoculants available in granular, powder, and liquid forms making the application more convenient.

The most important factor for reintegrating mycorrhizae into the cropland environment is to place mycorrhizal propagules near the seed or near the root systems of target plants. Granular inoculum can be banded with seed or seedlings. Powdered forms of inoculum can be mixed with seed before or during sowing. Liquid forms can be sprayed on seed and in-furrow, or drenched “over the top” for existing crops in porous soils. The form and application of the mycorrhizal inoculum depend upon the grower’s needs and equipment and is as easy as A, B, Seeds.

Myco-What?

Ten years ago the mention of mycorrhizal fungi to a turf manager might have met with a blank stare. Today’s managers are much more knowledgeable regarding the benefits of mycorrhizae. Research studies have shown us all how these specialized fungi can improve fertilizer utilization, rooting depth, establishment, and drought resistance of turf. New tools, such as the use of beneficial mycorrhizal fungi, allow turf managers to improve the condition of both turf and soil.

What are Mycorrhizae?

In their undisturbed natural environments, most grass species form a beneficial association with mycorrhizal fungi. The resulting structure is called a mycorrhiza, literally meaning “fungus-root.” Although there are several types of mycorrhizal fungi forming mycorrhizae with plants, the largest group, endomycorrhiza (also called arbuscular mycorrhizae) form with most grass species. Mycorrhizal fungi are present in soil as spores, and hyphae (filaments) in soil or as colonized roots.

Once the mycorrhizal association is established, it provides increased root surface area to support the exchange of nutrients between the fungus and the grass. These filaments form an extensive system that grows into the surrounding soil, providing numerous and various benefits for the grass plants. This network of filaments efficiently absorbs water and 15 major macro and micronutrients, transporting these materials back to the turf root system and into the host plant. Mycorrhizae are especially important for the uptake of nitrogen and phosphorus as well as many hard-to-acquire micronutrients. Conserving water and delivering fertility directly into the target turf grass is a key goal of turf managers. The mycorrhizal network improves water and nutrient utilization, which minimizes off-site groundwater movement of fertilizer. It also binds soil particles together which improves soil porosity and enhances the movement of air and water within the soil.

Mycorrhizae: Where are they?

Soils in natural settings are full of beneficial soil organisms including mycorrhizal fungi. However, research indicates that many common landscape practices such as site preparation, grading, removal of natural vegetation and heavy use of chemical pesticides and fertilizers often degrade the mycorrhiza-forming potential of soil. Construction site preparation activities such as removal of topsoil, compaction, erosion and simply leaving soils bare can also reduce or eliminate healthy and diverse populations of mycorrhizal fungi (Amaranthus et al. 1996; Doer et al. 1984; Dumroese et al. 1998, Amaranthus and Steinfeld 2003, Rider et al. 2007).

Research shows that putting greens constructed according to U.S. Golf Association standards generally lack mycorrhizal fungi at the time of sowing and that mycorrhizal populations are slow to establish in the greens (Koske et al. 1997, Hartin et al. 2007). Furthermore, laboratory analyses of root samples from hundreds of turfgrass areas across the U.S. indicate that the majority have less than 20 percent mycorrhizal colonization. Many samples were found to have no mycorrhizal colonization at all. New mycorrhizal products designed for the turfgrass industry are now restoring these ancient grass allies back to impacted soils.

Show Me the Data

Mycorrhizae are, by far, the most researched aspect of soil biology. Over sixty thousand studies of the mycorrhizal relationship with plants are available in the scientific literature. Studies have shown that grass species in the family Poaceae benefit greatly from mycorrhizal colonization in terms of growth and nutrient acquisition (Gemma and Koske 1989; Sylvia and Burks 1988; Hall et al 1984, Rider et al. 2007). Warm-season grasses such as bermudagrass with coarse root systems are particularly dependent upon mycorrhiza for sustained growth (Hetrick et al 1988; 1990). Recent data indicates that cool-season, finer rooted bentgrass species also form abundant mycorrhiza and benefit from the relationship, especially in soils in which the phosphorus levels are moderate or low (Gemma et al. 1995; Gemma et al 1997; Koske et al 1997). Recent findings of improved turfgrass establishment, root growth, fertilizer utilization, coverage have encouraged many turf managers to include mycorrhizal inoculations in their construction and maintenance practices (Hartin et al 2005, Rider et al. 2007). Turf areas often incur environmental stresses caused by compaction, frequent mowing, and artificial sandy substrates lacking nutrient and water holding capacities. The benefits of mycorrhizal inoculation are especially apparent in such high-stress situations.

Water, Water Everywhere?

Water conservation awareness has increased as water becomes an increasingly expensive and environmentally sensitive component of turf management. Research has shown that mycorrhizae can reduce moisture stress in grasses (Koske et al 1995; Auge et al. 1995; Allen et. al. 1991). Studies published in the Journal of Turfgrass Science state that creeping bentgrass inoculated with mycorrhizal fungus tolerated drought conditions significantly longer than non-mycorrhizal turf (Gemma et al. 1997). Mycorrhizal inoculated turf also recovered from drought-induced wilting more quickly than non-mycorrhizal turf. The data also shows that mycorrhizal turf maintained significantly higher (avg. 29% more) chlorophyll concentrations than non-mycorrhizal turf during drought events.

Faster Growth and Root Development

Research (Gemma et al, 1997; Hartin et al. 2005, Rider et al. 2007) indicates that mycorrhizal inoculation at the time of sowing turfgrass can increase its rate of establishment. This quick establishment of turfgrass in sandy soils has attracted the attention of golf course maintenance managers because the faster establishment and earlier playability have a significant economic payback. Other recent trials in Oregon and California demonstrated that mycorrhizal inoculants applied at the time of sowing doubled the percent of grass cover in the early establishment period and significantly increased the root biomass of treated turf.

Reduce Nutrient Loss and Pollution

Only a fraction of the synthetic fertilizers placed in U.S. soils is utilized by plants as intended. Much of these applied materials result in the movement of nutrients into groundwater or waterways and end up damaging the surrounding environment. Some are volatilized into the air, contributing to acid rain and climate change, while much of it travels past the root zone of the target plants, through the soil profile, and into groundwater and neighboring streams, lakes, and oceans.

Phosphorus is a nutrient that is essential to aquatic plant growth. Phosphorus pollution accelerates a process called eutrophication, which is essentially the biological death of a body of water due to depleted oxygen. When aquatic plants, such as algae, absorb an abundance of phosphorus, they can grow out of control.

One pound of phosphorus can result in the growth of 350-700 lbs. of green algae! Excess amounts of phosphorus and nitrogen cause rapid growth of phytoplankton, or algae, creating dense populations, or blooms. The algae ultimately sink and are decomposed by bacteria, depleting the bottom waters of oxygen. Like humans, most aquatic species require oxygen. When the oxygen in deep water is gone, fish and other species will die unless they move away to areas of suitable habitat. On the economic side, excessive algal growth due to nutrient pollution increases water treatment costs, degrades fishing, boating activities, and can impact tourism, property values, and even human health.

Soil biology is critical to capturing and storing fertility in the ground (Read et al. 1992). An acre of healthy topsoil can support an immense array of living organisms and the associated web of life that assimilates and captures long-term fertility (Amaranthus et. al 1989). It is clear that utilizing biological amendments is a necessary paradigm shift for the utilization and conservation of soil nutrients that are available to managers today.

When to Use Mycorrhizae?

Turf areas are generally devoid of mycorrhizal populations following construction and site preparation (Gemma et al 1997, Hartin et al. 2005, Rider et al. 2007) and are prime candidates for achieving the benefits of the mycorrhizal inoculation. The inoculum can be incorporated during construction, by aerification, or “over the top”, if soils are porous and enough water is available to leach the mycorrhizal spores into the soil profile. This places the mycorrhizal propagules in the rooting zone where they will be effectively utilized. A good time to apply the inoculum is when roots are most active such as spring and fall. Mycorrhizal colonization assessments are simple tests that are now available at many soil testing laboratories.

Use Diverse Species of Mycorrhizal Fungi

Natural areas generally contain an array of mycorrhizal fungal species. Not all mycorrhizal fungi have the same capacities and tolerances. Because of the wide variety of soil, climatic, and biotic conditions characterizing turf environments, it is improbable that a single mycorrhizal fungus could benefit all turf grasses and adapt to all conditions. Mycorrhizal fungi species have varying abilities to protect turf against drought. Likewise, some mycorrhizal fungi are better at producing enzymes that facilitate mineral uptakes such as phosphorus and iron. Still, other mycorrhizal fungi can better access organic forms of nitrogen. Selecting mycorrhizal products containing several mycorrhizal species can provide a range of benefits to the plant not found with only one species.

Making a Commitment

How often do you think about the impact of your management practices on turf and environmental quality? Annually? Weekly? Daily? If you responded weekly or daily you are probably a person who is interested in environmentally-friendly products that will improve turf and soil quality. Mycorrhizal fungi are not new, trendy, genetically engineered organisms. These specialized fungi have been fundamental to the survival and growth of plants for over 400 million years.

Scientific advancements in the culture of certain beneficial mycorrhizal species are rapidly creating more cost-effective mycorrhizal products in the turf management marketplace. Mycorrhizae can help lower costs over the long run. A living soil and healthy turf will retain nutrients, build soil structure, reduce stress, and minimize certain maintenance activities. The appropriate use of mycorrhizae in turf programs will not only benefit the environment but will also improve coverage, rooting, fertilizer utilization, and drought resistance. Protecting the environment has never made more sense. Myco-what? This is definitely a question of the past.

Abstract.

Numerous studies have shown that ectomycorrhizal fungi can profoundly affect conifer performance by facilitating nutrient and water uptake, maintaining soil structure, and environmental extremes. However, fertilizing and irrigating practices in seedling production nurseries are very different than field conditions at harsh outplanting sites. More information is needed on the ability of specific mycorrhizal fungi to establish at the nursery and improve seedling performance in the outplanted environment. This study was conducted to test the ability of a specific ectomycorrhizal fungus, Rhizopogon rubescens, inoculated onto the root systems of plug-1 ponderosa pine (Pinus ponderosa) seedlings grown in fumigated and nonfumigated bare-root nursery beds to influence conifer establishment on two harsh, dry sites in southwest Oregon, U.S. After outplanting, survival of Rhizopogon-inoculated seedlings were significantly higher than noninoculated seedlings at both field sites (p < 0.05). Survival averaged 93% for Rhizopogon-inoculated seedlings and 37% for noninoculated seedlings at the Central Point site. Survival averaged 71% for Rhizopogon-inoculated seedlings and 41% for noninoculated seedlings at the Applegate site. Field survival did not differ significantly for ponderosa pine seedlings grown in fumigated compared to nonfumigated beds. Seedling height did not differ significantly between Rhizopogon-inoculated and noninoculated ponderosa pine seedlings or fumigated and nonfumigated beds in the nursery or outplanting sites. Foliar analysis at the Applegate site indicated significantly higher phosphorous contents for Rhizopogon-inoculated seedlings. Results from this study indicate that Rhizopogon inoculated plug-1 ponderosa pine survive at a much higher rate on dry, harsh sites in southwest Oregon. Poor survival by noninoculated pine seedlings grown in both fumigated and nonfumigated beds and outplanted on harsh sites indicate that field survival should be considered one of the more important criteria for selection of Rhizopogon species suitable for nursery inoculation.

Key Words.

Rhizopogon spp.; ponderosa pine; Pinus ponderosa; mycorrhizae; mycorrhizal fungi; spore inoculation; fumigation; transplanting; survival; drought tolerance; conifer nursery. Throughout the western United States, ponderosa pine (Pinus ponderosa Dougl. ex Laws.) trees are planted extensively on a variety of sites in urban, suburban, and forest environments. Disturbed, compacted soils and hot, dry sites are commonly encountered. First-year mortality of planted trees can be high under harsh conditions (Preest 1977; Peterson and Newton 1985; Amaranthus and Perry 1987; Amaranthus and Malajczuk 2001) and foresters, landscapers, and arborists are always interested in cultural practices at the nursery that may improve tree survival and performance. Conifer tree establishment depends on rapid root and ectomycorrhizal formation on dry sites difficult to regenerate (Amaranthus and Perry 1989). In the arid western United States, transpiration potential during the growing season can exceed soil water availability, killing or reducing growth of nonirrigated seedlings. Ectomycorrhizae enhance water uptake by their hosts (Trappe and Fogel 1977; Reid 1979; Parke et al. 1983), although tolerance to low water potentials vary widely among mycorrhizal species (Mexal and Reid 1973; Theodorou 1978; Parke et al. 1983). Amaranthus and Malajczuk (2001) found Rhizopogon rubescens mycorrhizal colonization of longleaf pine seedlings (Pinus palustris Mill.) significantly reduced plant moisture stress at low soil moisture levels. Plant moisture stress levels averaged 78% higher for noninoculated seedlings compared to Rhizopogon-inoculated seedlings at low soil moistures. Theodorou and Bowen (1970) also observed that P. radiata seedlings inoculated with R. luteolus survived a particularly dry summer better than nontreated seedlings. Sands and Theodorou (1978) found leaf water potentials of Rhizopogon-inoculated seedlings were lower than for noninoculated seedlings.

Numerous studies have shown improvement of outplanting performance of Rhizopogon-inoculated seedlings in conifer establishment. (Volkart 1964; Theodorou and Bowen 1970; Theodorou 1971; Momoh 1976; Castellano and Trappe 1985; Ekwebelam and Odeyinde 1985, Amaranthus and Perry 1989, Castellano 1996). Nutrient acquisition is considered a major factor improving seedling growth. Significantly increased uptake of phosphorus has been reported for mycorrhizal inoculated conifer seedlings(Theodorou and Bowen 1970; Lamb and Richards 1971, 1974; Skinner and Bowen 1974a, 1974b; Chu-Chou 1979, Chu-Chou and Grace 1985), as well as potassium (Theodorou and Bowen 1970; Lamb and Richards 1971), sodium (Melin et al. 1958), total nitrogen (Chu-Chou and Grace 1985), and ammonia forms of N (Finlay et al. 1988).

Considerable effort and expense is directed toward site preparation at many suburban and urban sites. Mycorrhizal inoculum density and viability are often reduced as of a result of site preparation activities (Amaranthus et al. 1994, 1996; Dumroese et al. 1998). Amaranthus et al. (1996) found significant reductions in mycorrhizal abundance and diversity, including Rhizopogon spp. with moderate to high levels of organic-matter removal and soil compaction. Rhizopogon spp. produce belowground fruiting bodies that require animals to spread spores via fecal pellets. They do not produce airborne spores, which makes it unlikely that Rhizopogon mycorrhizal fungi would quickly be introduced from surrounding natural areas to disturbed urban and suburban sites.

The role of mycorrhizal fungi in the health and vigor of trees in stressful environments is well documented. However, more information is needed regarding establishing specific native mycorrhizal fungi in conifer tree nursery environments to increase seedling survival on harsh planting sites. Nursery inoculation of mycorrhizal fungi selected to promote survival and growth in a dry forest, suburban, or urban environment could be an important tool for foresters, landscapers, and arborists. This study was conducted to test the ability of a specific ectomycorrhizal fungus, R. rubescens, inoculated onto the root systems of plug-1 ponderosa pine seedlings grown in fumigated and nonfumigated bare-root nursery beds to influence outplanting performance on two harsh dry sites in southwest Oregon.

MATERIALS AND METHODS Nursery Procedures

On July 1, 1999, ponderosa pine seeds were sown in 2 in3 cells in Stryoblock™ containers at the J. Herbert Stone Nursery in Central Point, Oregon. On July 12, emerging ponderosa pine seedlings were inoculated with 100,000 spores each of the mycorrhizal fungus R. rubescens using an injection of a liquid suspension via a traveling irrigation boom. Spores were applied as a soil drench following maceration of R. rubescens sporocarps for 10 minutes in distilled water. Spore concentrations were determined with a haemacytometer. Foliar fertilizer (250 ppm N, 31 ppm P, and 158 ppm K plus micronutrients) was applied each irrigation during the rapid growth phase. Greenhouse temperatures were held between 65°F and 75°F. In early September 1999, seedlings were hardened-off by reducing irrigation and changing the fertilizer rates (50 ppm N, 60 ppm P, and 150 ppm K plus micronutrients). On September 22, 1999, ponderosa pine seedlings were inoculated again with 100,000 spores each of R. rubescens using the same inoculation procedure. No pesticides were used on the crop during this period.

On September 29, 1999, Rhizopogon-inoculated and noninoculated ponderosa pine were extracted and transplanted into fumigated and nonfumigated bare-root nursery beds at J. Herbert Stone Nursery. At that time 6 Rhizopogon inoculated and noninoculated container seedlings were examined for the percentage of colonization by the mycorrhizal fungus R. rubescens. Mean colonization by R. rubescens on inoculated seedlings was 8%, while no Rhizopogon was present on noninoculated seedlings. Fumigated beds were treated with methyl bromide the prior year, while nonfumigated beds had not been fumigated since October 1996. Prior to transplanting, 200 lb per acre of ammonium phosphate (16-20-0) and 200 lb per acre of potassium sulfate (0-0-50-53) were incorporated into the soils.

After transplanting, seedlings were grown using standard cultural practices for bare-root production. Seedlings were fertilized with 242 lb of N in the form of ammonium nitrate and ammonium sulfate during spring 2000. Root wrenching occurred four times during spring and summer 2000. No pesticides were used on the transplant crop. Seedlings were lifted on January 8, 2001, and those not meeting minimum seedling diameters of 5 mm and seedling height of 13 cm were discarded. Seedlings with poorly developed root systems or J-roots were also removed. Diameters, heights, and root volumes of seedlings to be outplanted were measured on 30 seedlings each from fumigated, nonfumigated, Rhizopogon-inoculated, and noninoculated plots. No significant differences in seedling diameters, heights, or root volumes (p = 0.05) were measured between treatments. Seedlings were placed in cold storage for 4 months until they were outplanted.

Outplanting Procedures

Seedlings were outplanted in two locations in southwest Oregon—the Central Point and Applegate study sites. The Applegate study site is in a small valley at 385 m elevation in the Siskiyou Mountains. Historical annual precipitation averages 650 mm, less than 10% of which falls from mid May through mid-September. Soils are fine loamy, mixed mesic Ultic Haploxeralfs, 60 to 100 cm deep, formed in granitic colluvium and underlain by weathered granitic bedrock. Soils are classified in the Holland series (Soil Conservation Service 1979). Surface layers (to 18 cm) are dark grayish brown to brown sandy loams. Percentages of sand, silt, and clay are 52, 24, and 24 respectively. The study area is on a southwest-facing, gentle (< 5%) toe slope just above the valley bottom. Soil moisture was at field capacity (28%) at the time of outplanting ponderosa pine. The Central Point site is located at the J. Herbert Stone Nursery near Central Point, Oregon, at 426 m elevation on an early level slope (< 5%). Historical annual precipitation averages 500 mm, less than 10% of which falls from mid May through mid-September. Soils are coarse-loamy, mixed, mesic Pachic Haploxerolls, more than 100 cm deep, formed from granitic and metamorphic alluvium. They are classified in the Central Point series. Surface layers are black, sandy loams about 40 cm thick. The planting site is located in an unirrigated field. Soil moisture at the time of planting was at field capacity (15%) at time of planting.

Seedlings were outplanted on May 9, 2001, at both sites. At each site, 16 plots (2 × 2 m) were established for field assessment of Rhizopogon-inoculated/noninoculated and fumigated/nonfumigated treatments. Each area was planted with randomly assigned treatments of nine seedlings each in a 3 × 3 array at 40 cm spacing. Each of the 16 plots were separated by 1 m buffers. The treatments were (1) Rhizopogon-inoculated/fumigated beds, (2) noninoculated/ fumigated beds; (3) Rhizopogon-inoculated/nonfumigated beds; and (4) noninoculated/nonfumigated beds. Each treatment was replicated four times at each site. In September 2001, tree heights at ground line were measured on surviving seedlings and the number of surviving seedlings tallied for each treatment area.

Laboratory Procedures

Before outplanting, five randomly selected seedlings were examined for presence of Rhizopogon ectomycorrhizae for each of the 16 plots. Roots were gently washed free of soil and extraneous material and subsampled in three cross sections, 1.5 cm broad, of the entire root systems in upper, middle and lower positions, respectively. All active tips were tallied as Rhizopogon, other mycorrhizal or nonmycorrhizal from characteristics observed through a dissecting microscope (2× by 10× magnification). Mycorrhizal tips were separated by type according to characteristics observable through a dissecting microscope (2× to 10× magnification). Rhizopogon mycorrhizae identification was verified using color, surface appearance, branching, morphology, degree of swelling, length, and characteristics of rhizomorphs. Rhizopogon rubescens mycorrhizae were creamy white and developed a gradient of yellow and reddish coloration with maturity and upon bruising. The R. rubescens mycorrhizae had a two-layered mantle and abundant rhizomorphs developing a compact coralloid morphology with maturity. In September 2001, pine needle samples were collected from four randomly selected seedlings from each treatment at the Applegate site. Samples were analyzed for total N, P, and K (Kjeldahl digest with ammonia and orthophosphate read on an autoanalyzer).

Statistical Procedures

The experimental design was a randomized block. ANOVA was selected as the primary analysis technique. ANOVAs were performed separately for seedling survival, height, foliar nutrients, and mycorrhizal colonization (Steel and Torrie 1980). Means comparisons were calculated using Fisher’s LSD. Residuals from the performed ANOVAs were examined using, normal probability plots, tests that the residuals come from normal distributions, and plots of residuals versus predicted values. Before analysis, data were logarithmically transformed to compensate for log-normally distributed values (Steel and Torrie 1980).

RESULTS AND DISCUSSION

Ponderosa pine outplanting survival following Rhizopogon inoculation was significantly higher compared to noninoculated seedlings (p < 0.05; Figure 1 and Figure 2*). The average seedling survival for Rhizopogon-inoculated seedlings was 93% compared to 37% for noninoculated seedlings for the Central Point site. The average seedling survival for Rhizopogon-inoculated seedlings was 71% compared to 41% for noninoculated seedlings for the Applegate site. Seedling height at the time of outplanting and after the first growing season in the outplanting environment was not significantly different for any treatment and site combination (Figure 3).

Rhizopogon mycorrhizal colonization was significantly higher on Rhizopogon-inoculated seedlings compared to noninoculated seedlings (Figure 4). Seedlings from fumigated beds had higher Rhizopogon colonization (28%) compared to nonfumigated beds (17%) and noninoculated seedlings from fumigated and nonfumigated beds (1%). However, there were no statistical differences between survival of Rhizopogon-inoculated seedlings from fumigated and nonfumigated beds (Figure 5).

Foliar phosphorous contents were significantly higher on Rhizopogon-inoculated seedlings outplanted from both fumigated beds and nonfumigated beds (Figure 6). Phosphorous percentages were 90% and 60% higher on Rhizopogon-inoculated seedlings outplanted from fumigated beds and nonfumigated beds, respectively, compared to noninoculated seedlings. Foliar nitrogen and potassium levels were higher but not significantly different from noninoculated seedlings (p < 0.05) from fumigated and nonfumigated beds planted at the Applegate site.

Seedlings planted in the western United States are usually subjected to low rainfalls and high temperatures during the summer months after spring outplanting. In our study, both outplanting areas represent typical harsh sites encountered in southwestern Oregon. Rainfall in the months following outplanting of our study was very low (56 mm between May 1 and October 1, 2001), and afternoon ambient air temperatures were high (temperatures exceeded 32°C on 49 days between May 1 and October 1, 2001). As a result, many seedlings at the Central Point site showed signs of wilting and mortality as early as the end of June, 6 weeks after outplanting. Seedlings continued to die as the summer progressed and soils dried out. At both outplanting sites, ponderosa pine seedlings with roots colonized by Rhizopogon mycorrhizae, however, survived significantly better than noncolonized seedlings. This finding may be related to the properties and functions of Rhizopogon that decrease plant moisture stress and promote drought tolerance as soils dry out. Amaranthus and Malaljczuk (2001) found that at high soil moisture contents, there were no significant differences in plant moisture stress between Rhizopogon-inoculated and noninoculated of longleaf pine seedlings. But as soils dried down to as low as 4% soil moisture, differences in plant moisture stress between inoculated and noninoculated seedlings became significant, with inoculated seedlings averaging 9.8 bars and noninoculated seedlings averaging 20 bars.

The mechanism by which Rhizopogon mycorrhizae reduce plant moisture stress in dry soil conditions is becoming better understood. On examination of the excavated Rhizopogon inoculated pine seedling root systems, we observed spongy mycorrhizal mantles and abundant rhizomorphs (Figure 7). Hydration and slow release of water to the tree from spongy fungus mantles and rhizomorphs during drought conditions could buffer seedlings and help reduce plant moisture stress. Spongy mantles and rhizomorphs have been noted and described in numerous Rhizopogon studies (Massicotte et al. 1994; Molina and Trappe 1994; Agerer et al. 1996). Rhizomorphs play an important role in water storage and movement (Duddridge et al. 1980; Brownlee et al. 1983; Read and Boyd 1986). Parke et al. (1983) and Dosskey et al. (1990) demonstrated enhanced tolerance to drought stress of Douglas-fir (Pseudotsuga menziesii) seedlings inoculated with R. vinicolor and attribute this enhancement in part to rhizomorph production and function in water storage and transport.

Benefits of inoculating seedlings with Rhizopogon mycorrhizae might not be apparent to managers of bareroot and container nurseries who are trying to produce larger seedlings. The lack of aboveground differences between inoculated and noninoculated seedlings in this study at the nursery is commonly observed by many nursery managers who inoculate with ectomycorrihzae. Why aboveground differences are not apparent in nurseries could be due to the relatively low moisture stress and high soil nutrient levels typical of nursery environments. In our study, nursery seedlings were never subjected to stresses that exceeded a pre-dawn moisture stress of 10 bars. Soils were kept moist for most of the time that seedlings were in bare-root beds except for a 4 to 6 week period in late summer 2000 when the soils were allowed to dry to induce seedling hardening. Since mycorrhizae support seedlings when moisture and nutrients are limiting, their function in the nursery environment might be of limited advantage.

Outplanting benefits of nursery Rhizopogon-inoculation, however, are well documented. Results from studies throughout the world have demonstrated the importance of Rhizopogon spp. as ectomycorrhizal symbionts in the successful establishment of conifers. As early as 1927, Kessel recognized R. luteolus as being among the first fungi to fruit in association with scattered “healthy” radiata pine in Australian nurseries. Chu-Chou (1979) reemphasized the importance of Rhizopogon in conifer plantations and nurseries in New Zealand. Chu-Chou and Grace (1981, 1983) later discovered R. vinicolor and R. parksii to be dominant ectomycorrhizal fungi of introduced Douglas-fir seedlings in nurseries and plantations. In Nigeria, Momoh (1976) has found R. luteolus associated with vigorously growing introduced pines. Rhizopogon ectomycorrhizae also have been associated with the establishment of conifers in Africa (Donald 1975; Fogel 1980; Ivory 1980), Puerto Rico (Volkart 1964), Europe (Levisohn 1956, 1965; Gross et al. 1980; Jansen and de Vries 1989; Parlade and Alvarez 1993; Parlade et al. 1996), New Zealand (Birch 1937; Chu-Chou and Grace 1981, 1983), South America (Garrido 1986), and the United States (Baxter 1928). More recently, the importance of Rhizopogon in increased seedling performance in the field following nursery inoculation was demonstrated in the Oregon Coast Range. Amaranthus and Perry (1994) inoculated nursery-grown containerized Douglas-fir seedlings from six families with spores of R. vinicolor. Inoculated and noninoculated seedlings from all families were outplanted in the Oregon Coast Range. Rhizopogon vinicolor-colonized seedlings from all families had significantly greater height growth (six of six families) and basal area growth (five of six families) compared to noninoculated seedlings.

The finding of no significant difference between survival of fumigated and nonfumigated seedlings has implications to nurseries that are moving away from using soil sterilants. Soil fumigation with broad-spectrum biocides is a nonselective means of killing soilborne pathogens in tree seedling nurseries (Linderman 1994; Marx et al. 1979). Nursery practices that utilize methyl bromide or other soil sterilants are known to reduce or eliminate mycorrhizal fungi (Lee and Koo 1985; Davies 2002). At J. Herbert Stone Nursery, the soils of the nonfumigated treatments had been fumigated 3 years before the seedlings were transplanted in this study. During this period, changes in soil biological composition and the reintroduction of mycorrhizae, including Rhizopogon spp., have been slow. Rhizopogon spp. produce belowground fruiting bodies that do not disperse their spores through the air, thus making reintroduction from natural areas more difficult. The results of our study suggest that if mycorrhizae-colonized seedlings are to be produced in bare-root fields, inoculation with specific mycorrhizae will be necessary until a desirable population of mycorrhizae becomes established in nonfumigated nursery fields.

The importance of ectomycorrhizal fungi in the uptake and translocation of nutrients to their host plants has been the underlying principal in numerous studies of conifers. Of particular importance is the role of ectomycorrhizal fungi in phosphorous nutrition. Ectomycorrhizal fungi produce acid phosphatases, a special type of root exudate that hydrolyses organically bound phosphorous. Bowen and Theodorou (1968) found that R. roseolus cultures were able to solubilize rock phosphate, and Theodorou (1968) also indirectly showed substantial phosphatase activity by R. roseolus. Skinner and Bowen (1974) demonstrated the uptake and translocation of phosphate via mycelial strands of pine mycorrhizae. Ho and Trappe (1987) found that six Rhizopogon spp. tested produced acid and alkaline phosphatases as well as nitrate reductase, an enzyme that aids the acquisition of nitrogen. Ho and Trappe (1980) report that R. vinicolor produced high levels of nitrate reductase compared to other ectomycorrhizal fungi. In our study, Rhizopogon-inoculated pine seedlings had significantly increased levels of foliar phosphorous compared to noninoculated seedlings in one growing season after outplanting. Rhizopogon-inoculated seedlings also had increased foliar levels of nitrogen and potassium, but differences were not significantly different. The best documented mycorrhizal effect in the literature is that mycorrhizal plants take up more soil phosphorous than nonmycorrhizal plants do. In our study, we see a similar P effect, but it is unlikely that improved phosphorous nutrition had a substantial effect on seedling survival.

Mycorrhizal fungi play a key role in the health and vigor of trees in stressful environments. In southwest Oregon, dry spring and summer conditions often result in significant conifer mortality upon outplanting. Results from this study indicate that Rhizopogon inoculation at the nursery can help seedlings survive and establish on difficult sites. Nursery inoculation of specific mycorrhizal fungi, such as Rhizopogon spp., selected to promote survival and growth in dry and disturbed forest, suburban, and urban environments could be an important tool for foresters, landscapers, and arborists.

What Are Mycorrhizae?

“Myco” – “rhiza” literally means “fungus” – “root” and describes the mutually beneficial relationship between the plant and root fungus. These specialized fungi colonize plant roots in a symbiotic manner and extend far into the soil. Mycorrhizal fungal filaments in the soil are truly extensions of root systems and are more effective in nutrient and water absorption than the roots themselves. More than 95 percent of terrestrial plant species form a symbiotic relationship with beneficial mycorrhizal fungi, and have evolved this symbiotic relationship over the past several hundred million years. These fungi predate the evolution of terrestrial plants, and it was the partnership with mycorrhizal fungi that allowed plants to begin to colonize dry land and create life on Earth as we know it.

The mycorrhizal symbiotic relationship centers on the plant’s ability to produce carbohydrates through photosynthesis and share some of these sugars with the fungus in return for otherwise unavailable water and nutrients that are sourced from the soil or growing media by the extensive network of mycelial hyphae produced by the fungus. It’s a two-way relationship of sharing resources between two species, thus a classic symbiotic mutualism. The endomycorrhizal fungi rely on the plant, and the plant’s performance and survival are enhanced by the fungus.

How is this Symbiosis Established?

Mycorrhizal fungi can colonize plants from three main sources of inoculum: spores, colonized root fragments, and vegetative hyphae. Collectively, these inoculants are called “propagules,” and this is the standard unit of measure that is listed on most commercially available mycorrhizal products.

To colonize plant roots, these propagules must be present in the substrate and in close proximity to actively growing roots of a compatible plant. The growing root tips emit root exudates as they push through the substrate which signal the fungi to colonize the roots and establish the symbiosis. Once the roots are colonized, then the process is self-sustaining as the mycelia continue to grow with the plant’s root system and additional spores and hyphae are produced.

AMF propagules can be incorporated into the substrate prior to or during planting or they can be top-dressed on the surface and watered into a porous substrate. They can also be applied as a dip or slurry at the time of sticking a cutting, seeding, or at the time of transplanting. The propagules can also be applied as a drench to the soil and watered-in, applied to the outer surface of the rootball before transplanting, or used in transplant hole and backfill soil.

What are the Main Benefits of Mycorrhizae? There are numerous documented benefits that mycorrhizal fungi provide to plants. The key benefits that mycorrhizae provide to professional growers are Root System Enhancement, Improved Nutrient Efficiency, and Increased Water Absorption & Utilization.

What are Some of the Other Benefits of Mycorrhizae?

The symbiotic relationship with mycorrhizal fungi provides many additional benefits to plants and their environments, along with the top-three listed above. These additional benefits include Improved Soil Structure, Greater Transplant Success, Increased Stress Tolerance, Reduced Nutrient Runoff, and many more.

Who Can Benefit from Mycorrhizal Fungi?

This biological or “bio rational” technology, as we like to call it, is beneficial to every industry involving soils, plants, and people. These symbiotic organisms have been relied upon for successful reforestation and restoration projects for decades. In agriculture, mycorrhizal fungi are partnering with plants in symbiosis to contribute to sustainably feeding our growing global population, even in drought-affected areas, salty soils, desertified farmland, etc. Professional horticulturists, including greenhouse and nursery growers, can also experience the benefits of mycorrhizae in their own growing protocols to grow heartier, more vibrant, and more resilient plants for retail sale and landscape installations. Landscape architects, installers, and maintenance workers have been utilizing mycorrhizal inoculants in transplanting and sustainable landscape design for at least the last couple of decades. Even homeowners who are planting gardens and/or caring for their lawns and landscapes can now utilize this technology, as more and more mycorrhizal retail products are showing up on shelves in garden centers.

What are the Different Types of Mycorrhizal Fungi?

How Many Species of Mycorrhizae do I Need?

One of the many benefits of adding mycorrhizae into your growing practices is the fact that these beneficial symbiotic organisms are involved in building a healthy ecosystem for your plants within the growing media rhizosphere. And like any healthy ecosystem, biodiversity is very important. Therefore, selecting products with greater numbers of species of the types of mycorrhizal fungi that you need (either endo mycorrhizae, ectomycorrhizae, or both), will offer greater benefits to your plants, throughout their entire life cycles.

Research has shown that the diversity of mycorrhizae in the plant’s root system is important, as these different species of mycorrhizae provide different benefits to the plant under variable circumstances. For instance, some species are better at assisting in nutrient uptake, while others are more proficient in assisting the plant with water efficiency, and others are responsible for mitigating toxins and salts from reaching the plant’s vascular system. Research has also shown that different species of mycorrhizae provide different benefits during different seasons, with some doing the heavy lifting early in the growing season, and others kicking in during the warmer drier months, and others providing benefits towards the end of the growing season or throughout the winter.

Therefore, we recommend choosing products with greater diversity (at least 4 species in endomycorrhizal products, and at least 7 species in ectomycorrhizal products), in order to ensure that you are providing the ideal soil microbiome for your growing operation, landscape installation or maintenance, restoration project, arbor care, etc.

Hidden from view beneath the soil surface in the farmer’s field there is a relationship between fungi and plants that is fundamental to life on the planet. Fungi can’t make their own food, they have to absorb their nourishment from living or dead organic matter. Organisms like fungi help assure the earth’s resources recycle as they should. There is one particular group of fungi that works in cooperation with important crop species. This article will shed some light on this special “farmers’ fungus” that pays big dividends. We have come to understand that in natural habitats, plant roots are a complex mixture of both fungi and plant. This relationship is called a “mycor-rhiza” which literally means ‘fungus-root’. Approximately nine out of every 10 species of plants form an association with these specialized mycorrhizal soil fungi in order to thrive. The plant needs the fungus and the fungus needs the plant. The fungus is responsible for getting the nutrients and water from the soil, and in return, it gets carbohydrates from the plant (figure 1). This is what is called a “symbiotic” relationship; one in which both plant and fungus benefit. The fossil evidence indicates that this plant/fungus relationship dates back over 460 million years.

What are they?

The body of the fungus consists of very thin strands called hyphae (figure 2). In healthy soils, these strands grow from within the root cells of the crop and spread out into the soil, greatly increasing the surface area of the root system. The most widespread type of mycorrhizal relationship are known as arbuscular mycorrhizae (also known as “endo” mycorrhizae) and are formed by most agricultural plants. These plants include most grains, vegetables, fruit and nut trees, vines and turf grasses.

What they do

The mycorrhizal relationship effect on the root system is dramatic. Most of the absorbing area of the root system is actually fungal hyphae. Hyphae are much thinner than roots or root hairs and are able to penetrate the tiniest pores in the soil. A thimbleful of healthy soil can contain miles of fungal hyphae! As a result, the efficiency of the plants’ nutrient and water uptake is increased enormously. Agricultural soil often contains abundant nutrients but availability to the crops themselves can be limited. Research demonstrates that mycorrhizae are particularly important in mobilizing phosphorus, nitrogen, zinc, iron, calcium, magnesium, manganese, sulfur and other tightly bound soil nutrients, transporting them back to the plant. This plant-fungus relationship can pay of big on the farm. Crop plants become able to absorb soil nutrients previously unavailable and utilize fertilizer inputs much more efficiently. The result is often significant savings in fertilizer costs (figure 3).

Water, water everywhere?

Agriculture’s need for fresh water is growing faster than nature can provide. It’s quickly becoming one of the key resource issues of the 21st century. How do natural areas provide for such luxuriant plant growth without irrigation? One key factor are the mycorrhizal threads attached to plant roots scouring the soil for available resources. They absorb water during periods of adequate soil moisture, then retain and slowly release them to the plant during periods of drought. Natural areas have achieved a level of drought tolerance that far exceeds agricultural areas partially because an enormous web of mycorrhizal threads act as a sponge, protecting plant communities from extreme moisture deficits. The mycorrhizal threads can penetrate into the small soil pores to access pools of water that are unavailable to the thicker roots. An extensive body of research has documented the importance of the mycorrhizal relationship for efficient water use and drought protection for a wide array of important crop species. The ever-increasing cost and declining quality of water are formidable issues facing farmers today. Today, mycorrhizal fungi can be a powerful tool for farmers seeking to improve water-use efficiency and lower irrigation costs.

Does my farm have mycorrhizal fungi?

Some modern agricultural practices reduce the biological activity in soil. Fungicides, chemical fertilizers, cultivation, compaction, soil erosion and periods of fallow can all adversely affect beneficial mycorrhizal fungi. Extensive testing of agricultural soils indicates that many intensively managed lands such as agricultural fields lack adequate populations of mycorrhizal fungi. Farming extensive acreage affects the mycorrhizal relationship in two fundamental ways. First, it isolates the crop plant from the beneficial mycorrhizal fungi available from natural settings. Secondly, it increases the need for water, nutrients, and soil structure required to sustain a healthy crop. Once lost from a farm, arbuscular mycorrhizal populations are very slow to re-colonize, unless there is close access to natural areas that can act as a source of mycorrhizal spores and hyphae to re-populate the affected area. Arbuscular mycorrhizal fungi do not disperse their spores in the wind, but rather grow from root to root. The spores do not easily move long distances back to the farm soil from undisturbed natural sites. Unfortunately, growing crops immediately adjacent to undisturbed natural ecosystems is not always an option on the modern farm.

How do I use mycorrhizal inoculants on my farm?

A farmer can enhance crop root growth, nutrition and yield, reduce irrigation and ameliorate many problems resulting from intensive agriculture by inoculating with mycorrhizal fungi. A more sustainable approach to crop establishment and growth includes using mycorrhizal fungi as an inoculant before, during, or following planting. The goal is to create physical contact between the mycorrhizal inoculant and the crop roots. They can be sprinkled onto roots during transplanting, banded with or beneath seed, used as a seed coating or watered in via existing irrigation systems. Treating seed either before or during sowing produces excellent results. Just one pound of a mycorrhizal inoculant concentrated powder can easily treat enough seed to plant one acre. The type of inoculum product and application method depends upon the conditions and needs of the crop and farmer. Generally, mycorrhizal application is easy, inexpensive, and requires no special equipment. Liquid forms of mycorrhizal inoculants are becoming very popular due to the ease of handling, mixing, storage, and their effectiveness in penetrating many soil types and treating existing plants. It is also now possible to have vegetables, fruit and nut crops which begin their life cycle in a nursery inoculated with mycorrhizal fungi. Unfortunately, most crop plants raised in nurseries are started in sterile soils and receive intensive fertilization, water, and pesticides. Although these artificial conditions can produce vast volumes of plants, they also result in non-mycorrhizal plants that are often poorly adapted to the eventual out-planted conditions on the farm where they will be subject to the harsher environment of the open field. Conversely, nursery-grown plants that have already been colonized with mycorrhizal fungi are better equipped to take advantage of soil resources and can establish rapidly and successfully in the field.

What about Fungicides?

Of course, mycorrhizae are fungi so it stands to reason that some fungicides will reduce or eliminate them from the soil and roots. Fortunately, research and experience indicates that certain types of fungicides do not adversely affect mycorrhizae. A list of common agricultural fungicides and their effects on mycorrhizae can be accessed at BioStim. Sometimes it helps to apply fungicides four to six weeks prior to the mycorrhizal treatment. Mycorrhizal inoculums may also be applied after the use of a fungicide. Follow manufacturers’ guidelines for the time required for the fungicide to “clear” the soil media.

Farm fungi pay dividends

Many mainstream agricultural markets are already benefiting from the use of mycorrhizal inoculums, and use continues to increase dramatically. Recent advancements in mycorrhizal research and application technology have made farm use of mycorrhizae easier and more cost effective than ever. The economic return for mycorrhizal inoculation can exceed its cost several-fold, not only from increased yields, but also by reduced fertilizer, and water costs. Using a mycorrhizal inoculant, Del Gates of North Dakota increased flax yields by 27%. Ron Miller’s wheat farm in Nebraska increased its yield of organic wheat by 42% by treating the seed with a mycorrhizal inoculant powder. Agronomists in California’s San Joaquin Valley documented a 20% yield increase of sorgum sudan grass at four different seeding rates following mycorrhizal inoculant treatment. Other studies have shown similar success with onions, alfalfa, melons, garlic, carrots, rice, strawberries, tomatoes, potatoes, almonds and a host of other crops where yield increases have ranged from 10 – 40%, often with reduced inputs and cost. Learning about the role of mycorrhizal fungi and the conditions that inhibit or promote their presence in the soil is the first step toward healthier crops, increased yields and lower costs. The next step is to add the fungi to the root zone when planting or transplanting and when restoring distressed soils. Good soil is a precious resource containing millions of years worth of nutrients and microorganism development. However, to be successful the farmer requires an appreciation of the “friendly fungus” that can pay big dividends.

Solar isn’t just for rooftops. It builds soil too!

It may come as a surprise to many to find that in healthy soil there is a poor relationship between plant productivity and the amount of applied nitrogen (N) or phosphorus (P). Recent research undertaken by Dr David Johnson and his team at New Mexico State University (NMSU) found there are other factors of much greater importance. What are these factors? And what can farmers do to optimise them?

The NMSU researchers discovered that plant growth is highly correlated with how much life—and what kind of life—is in the soil. In fact, microbial community structure, particularly the ratio of fungi to bacteria, had significantly more influence on yield than the concentration of inorganic N or P.

Given that flourishing communities of beneficial soil microbes are the ‘key’ to plant production, what is the secret to ensuring the right microbes are present in the right amounts?

Plants. That’s right. The most important factor for promoting abundant plant growth is to have green plants growing in the soil all year round.

The plant-microbe-soil connection

You may have heard that ‘plants take from the soil‘. Nothing could be further from the truth. Observe what happens in bare soil. It dies. Then it blows or washes away. If you could ’see’ what happens around the roots of actively growing plants you would want to have as many green plants in your soil for as much of the year as possible. The NMSU researchers found that planting diverse cover crops between cash crops resulted in better yields than the use of synthetic fertilisers and that wasn‘t all. Soil tests showed that the availability of essential minerals and trace elements increased. How does it work? Carbon inputs from living plants support the microbial activity required to improve soil structure, increase macro- and micronutrient availabilities and enhance soil water-holding capacity. In turn, these factors improve plant productivity. It’s a positive feedback loop.

The NMSU research team found that as cover drop density increased, the effect became quadratic, due to the synergies between living plants and soil microbial communities. That is, 1 + 1 = 4.

It all starts with photosynthesis

The energy needed to maintain flourishing soil ecosystems begins as light. This energy must cross two bridges in order to recharge the soil battery. First, the photosynthetic bridge. In the miracle of photosynthesis, light and CO2, are transformed to biochemical energy (carbon compounds) in the leaves of green plants.

Second, the microbial bridge. In the presence of beneficial bacteria and fungi photosynthetic rate increases and carbon ‘flows’ from plant roots into soil microbial intermediaries.

If one of these bridges has been blown (e.g. no green plants or compromised microbial communities), soil health declines.

Every summer, around 22 million hectares of Wheatbelt soils lie bare across eastern, southern, and western Australia. Herbicides are commonly used to maintain the soil in a plant-free state. Bare ground and low levels of biological activity result in declining structure, reduced infiltration, poor moisture retention, inadequately buffered pH, and an open invitation to weeds.

Take a step back in time…

Most of the temperate regions currently used for crop and pasture production supported vigorous, diverse groundcover at the time of European settlement. Summers in the southern half of the Australian continent have been hot and dry for thousands of years, yet there were more summer-active than winter-active plants in the original vegetation. This is an important point. It is not ‘natural’ for the soil to be bare over summer (or winter, for that matter).

Despite successive months of summer temperatures above 100° Fahrenheit (37 °C) and little or no rain, observers of the original groundcover reported it to remain remarkably green (Presland 1977). Active growth was possible during hot dry periods because the soil had a high water-holding capacity.

After many decades of the bare ground over summer—every summer—the water-holding capacity of our agricultural soils has significantly declined. The original groundcover contained more broadleaved plants (forbs) than grasses (Lunt et al 1998). Nutritious summer-active native legumes within genera such as Lotus, Hardenbergia, Kennedia, Cullen (formerly Psoralea), Glycine, and Desmodium were once abundant in their respective endemic areas, as were many food plants used by indigenous people, including yarn daisies (Microseris). As a general rule, broadleaved plants are more important than grasses for microbial diversity and nutrient cycling.

Not surprisingly, the most palatable and mineral-dense summer-active plants quickly disappeared from the original groundcover due to unmanaged grazing.

Restoring soil function

The more closely we can mimic the structure and function of year-round species-rich groundcover, the more productive and ‘problem-free’ our agricultural enterprises will be.

If there is sufficient moisture to support summer weeds there is sufficient moisture to support a summer cover crop. Furthermore, it is generally cheaper to sow a summer cocktail than to spray weeds. The purpose of a multi-species cover crop is to restore below-ground diversity which will, in turn, restore biological soil function (natural N-fixation and P-solubilisation) and plant productivity.

The nutrient sourcing and moisture retention benefits of diverse cover crops will continue to build in successive years as soil health improves.

Summer cocktails

Examples of broad-leaved plants that can be used in multi-species summer cover crops (cocktail crops) include sunflowers, buckwheat, chickpea, sunn hemp, amaranth, cowpeas, soybean, safflower, camelina, sugar beet, squash, and lab-lab. These can be combined with a range of plants from the grass family, including pearl and proso millet, sudangrass, forage sorghum, maize, etc. Aim for at least I0 species or varieties in your mix, with more broad-leaved plants than grasses.

Summer cocktail of sunflower, maize, soybean, cowpea, camelina, sugar beet, sudangrass, pearl millet, proso millet, pasja turnip, tillage radish, sweet clover, and squash on Menoken Farm. Cover crops can be either grazed or rolled while green, prior to the sowing of the follow-on crop.

Will there be a yield penalty?

Yield penalties may be observed In crops following summer groundcover If:

i) the summer groundcover did not include a diversity of broadleaved plants (aim for more non-grasses than grasses);

and/or

ii) high rates of inorganic N (e.g. urea) or P (e.g. MAP, DAP) were applied to either the cover crop or the follow-on crop, damaging the microbial bridge. Note: Inorganic N has been applied previously, for several years in succession, N use must be reduced slowly, as populations of free-living N-fixing bacteria will initially be very low.

What’s N got to do with it?

Aside from water, nitrogen is frequently the most limiting factor to crop and pasture production.

Nitrogen is nitrogen, irrespective of the source, but the same nitrogen compounds can have opposite effects, depending on the way they enter the soil and the form in which they exist in plants.

This paradox has created much confusion.

It is neither natural nor healthy for crop and pasture plants to contain high levels of inorganic nitrogen (nitrite, nitrate, etc). Nitrogen is much safer and more productive when in an organic form.

Closing The Nitrogen Loop

The efficiency of the use of applied N is generally less than 50% due to losses from leaching, volatilization, and denitrification (Kennedy et al 2004). These inefficiencies cost farmers a great deal of money as well as contribute to environmental pollution.

Fortunately, biological N fixation is a spontaneous process when adequate carbon is available under actively growing plants, provided large amounts of synthetic N have not been applied. In biologically active soils, sugars and other carbon compounds exuded by plant roots support vast colonies of beneficial fungi and bacteria, which in turn produce sticky substances that glue soil parties together and enhance soil structure.

Once aggregates (small lumps) start to form, free-living nitrogen-fixing bacteria, which require a low partial pressure of oxygen, can begin their work of fixing atmospheric nitrogen. These bacteria are called associative diazotroph, ‘associative’ because they are only found inside aggregates attached to living plant roots or connected to plants via the hyphae of mycorrhizal fungi-and ‘diazotrophs’ because of their ability to use nitrogenase enzymes to fix atmospheric nitrogen.

The nitrogen fixed by associative diazotrophs does much more than support plant growth. It also makes a significant contribution to the soil food web and is essential to the formation of stable forms of soil carbon, such as hummus.

In addition to associative diazotrophs, mycorrhizal fungi are indispensable for closing the nitrogen loop. Their ability to transfer organic N from the soil food web into plant roots circumvents the need for nitrogen to be present in an inorganic form (Leake et al 2004, Leigh et al 2009).

The activities of mycorrhizal fungi also contribute to the rapid sequestration of soil carbon.

But here’s the rub.

The applicant on large quantities of inorganic N-such as found in urea, MAP, DAP, etc inhibits the activities of both associative diazotrophs and mycorrhizal fungi. Long-term use of these products results in a decline in soil structure, the decline in soil carbon-and ironically, a decline in soil nitrogen (Khan et al 2007, Mulvaney et al 2009).

Reducing N dependence

Where diverse summer cover crops are being grown to support soil microbial communities, it is advisable to reduce N use, but this must be done slowly, to provide time for free-living N fixing bacteria to re-establish. There is no need for synthetic N in the cover crop provided a variety of broadleaved plants, including legumes, are present. Nitrogen inputs in follow-on crops can be reduced to 80% in the first year, 50% In the second year, and 20% In the third year. In the fourth and subsequent years, the application of a very small amount of N (around 1kg/ha) will help to prime the natural nitrogen-fixing processes in soil. Remember, associative diazotrophs (the most important of the free-living N-fixing bacteria) and mycorrhizal fungi (needed for N transfer to plants) have only one energy source liquid carbon from an actively growing green plant. At the same time as you are weaning your soil off synthetic N, you must also be maintaining as much diverse year-round living groundcover as possible.

Will I need to add P?

Plant roots produce hormones called strigolactones that control root extension, lateral root development, and the production of root hairs. The presence of strigolactones in the soil also stimulates root colonization by mycorrhizal fungi (Czarnecki et al 2013). Vigorous root systems and symbiotic relationships with mycorrhizal fungi are essential for maximizing the ability of crop plants to obtain water, nitrogen, phosphorus, potassium, sulfur, calcium, magnesium, and a wide variety of trace elements such as zinc, copper, boron, manganese, and molybdenum.

Many of these elements are essential for resilience to climatic extremes such as drought and frost. The application of large quantities of water-soluble P such as those found in superphosphate, MAP, DAP, etc inhibits strigolactone production by plant roots. That is, the use of these products will reduce root extension, root hair development, and colonization by mycorrhizal fungi. The long-term results in destabilization of soil aggregates, loss of porosity, reduced aeration, increased soil compaction, and mineral-deficient plants.

In addition to having adverse effects on soil structure, the application of inorganic phosphorus is highly inefficient. Around 80% adsorbs to aluminum and iron oxides and/or forms calcium, aluminum, or Iron phosphates, which, in the absence of microbial activity, do not plant-available(Czarnecki et al 2013). Only 10-15% of fertilizer P is taken up by crops in the year of application.

In old and deeply weathered soils, biological processes are more important than chemical processes when it comes to making nutrients.

Your soil already contains sufficient P, but it will only be in a plant-available form when the right microbes are present. If levels of mycorrhizal colonization are high, there will be no need to add large quantities of inorganic P.

Cover crops (and follow-on crops) can be supported with biology-friendly products such as pelletized compost or liquids such as compost extract, worm leachate, or milk. Compost extract containing around 1kg/ha (no more) of each of N, P, and S, plus whatever trace elements are required (as determined by plant tissue test) should be sufficient in most situations.

Strategic grazing

Land can respond positive y to the presence of animals, but the way they are managed is extremely important. Strategic (high-density, short-duration) grazing of summer groundcover helps to stimulate biological activity and cycle nutrients tied up in plant material. Aim to graze no more than one-third to one-half of the biomass, using mob stocking or strip grazing techniques to ensure the soil surface is completely covered with trampled plant material (Jay Fuhrer, pers. comm.).

Where grazing is not an option, cover crops can be rolled. Menoken Farm.

Putting it all together

Changing fertilizer practice alone is not sufficient to improve soil health. Unless biology-friendly fertilizers are used in combination with diverse year-round living cover the essential microbes won’t be there to be supported. For the same reasons, the presence of summer groundcover alone is not sufficient-indeed it may prove detrimental. There will be a tie-up of N and a yield penalty in the follow-on crop unless key functional groups, particularly the associative diazotrophs and mycorrhizal fungi, are working together. This simply cannot happen if large amounts of inorganic N or water-soluble P are applied.

• Strategic grazing of summer groundcover helps cycle nutrients tied up in plant material. Aim to graze no more than 30-50% and trample the remainder onto the soil surface. If grazing is not an option, cover crops can be rolled while still green.

• There is no need for either synthetic N or P in your ‘summer cocktail’ provided a good range of broadleaved plants, including legumes, are present.

• Remember to wean off N slowly in the follow-on crop. Cut back to 80% in the first year, 50% in the second year, and 20% in the third year, then maintain levels at 1kg/ha/yr. If you feel you must, also apply 1kg/ha/yr of inorganic P and 1kg/ha/yr of S-but no more!

• Improved weed management is one of the many benefits of integrated land management. Most crop and pasture weeds are stimulated by nitrate. The current farming model is essentially creating the problem. Weeds become less of an issue under biological forms of cover cropping. This is partly to do with groundcover but more usually the result of closing the nitrogen loop.

• Above all, the capacity of the soil to absorb and hold water is critical for dryland crop and pasture production. Although it may seem counter-intuitive, the most effective method for improving soil structure and increasing water-holding capacity is to maintain active year-round plant cover, which increases soil carbon, supports microbial activity, and improves the ratio of fungi to bacteria.

From light to life

Diverse summer cover crops are sown with biology-friendly fertilizers are the fastest way to restore soil function in Wheatbelt soils. These principles also apply to dairy, beef, lamb, wool, and horticultural enterprises in the winter rainfall zone.

Sunlight intercepted by bare earth is converted to heat energy, driving evaporation and soil loss.

Sunlight intercepted by green leaves is converted to biochemical energy, fuelling soil life, enhancing soil structure, improving nutrient cycling, and increasing water-holding capacity.

Why not turn ‘light’ into ‘life’ on your farm?

Perhaps just try one paddock to begin? Your soil will love you- you will love your soil.