Soil health paper

The Five Principles of Soil Health

Soil health refers to soil’s capacity to function as a vital ecosystem that sustain plants, animals, and humans. Soil contains living organisms that perform functions required to produce food and fibre.

The idea of soil health emphasises the fact that soil is a living ecosystem which comprehends billions of bacteria, fungi, and other microbes. The soil ecosystem can be managed to provide nutrients for plant growth, absorb and store rainwater during dry periods, serve as a foundation for agriculture and provide habitat for soil microbes to keep the ecosystem functioning.[i]

 

Principle 1: Soil Cover

Anytime sunlight strikes bare soil, that sunlight is not being used to sequester carbon dioxide and to provide food and animal feed through photosynthesis. Soil cover provides numerous benefits that enhance the functioning of the soil ecosystem.

Controlling Wind and Water Erosion – soil cover protects soil from wind and water erosion.  The cover holds the soil in place along with valuable soil organic matter and nutrients.

Evaporation Rates – by providing shade from sunshine, soil cover reduces the soil evaporation rates, keeping more moisture available for plant use.

Soil Temperatures – cover helps to maintain the soil temperature in moderate range, keeping soil warmer in cold weather and cooler in hot weather.  The living organisms in the soil food web function best when soil temperatures are moderate.

Compaction – when rainfall hits bare soil, the energy from the raindrops causes soil compaction. Soil cover reduces soil compaction by dissipating that rainfall impact.

Suppressed Weed Growth – soil cover suppresses weed growth by limiting their access to sunlight.

Habitat – covered soil provides a habitat for soil ecosystem organisms that live above the ground.

 

Principle 2: Minimized Disturbance

There are three main types of soil disturbance: biological disturbance, often due to overgrazing which limits the plants ability to harvest CO2 and sunlight, chemical disturbance which may occur when applying fertilisers and pesticides and can disrupt the soil food web functions and physical disturbance due to, for instance, tillage.

Soil typically contains 45% minerals (sand, silt and clay), 5% soil organic matter, 25% water and 25% air. Water and air enter soil through pore spaces between the soil aggregates. Tillage may reduce and remove pore spaces from the soil, restricting water and air infiltration. By reducing soil porosity tillage may also cause water and wind erosion and water logging.

Tillage has been also found to reduce carbon content of the soil. [ii]

 

Principle 3: Diversity

Nature’s functions are based in biodiversity, while most conventional farming is monoculture.

Crop rotations mimic the nature’s plant diversity, benefiting the soil food web which improves water infiltration and nutrient cycling while reducing disease and pests. Crop rotations can be designed to include crops which are high water users, low water users, tap root, fibrous root, high and low carbon crops, nitrogen fixing legumes etc.

By increasing the diversity of your crops, you will also increase the biodiversity in the soil, leading to healthy soil which can efficiently cycle nutrients and make them available for plants. [iii]

 

Principle 4: Living Roots in the Soil

Perennial grasslands have both cool and warm season grasses. Adaptable plants in nature are able to grow from early spring to late autumn, allowing the plant roots to continually feed nutrients to the soil ecosystem. Cropping systems typically grow cool or warm season annual cash crops, which have a dormant period before planting and after harvest.

Cover crops can fill in the dormant period, providing nutrients for the soil ecosystem during the gaps. Cover crops can be incorporated as annuals, biennials, or perennials. Starting from small the farmers and ranchers can find the best fit for their operation.

Having living roots continuously in the soil can address many resource concerns:

• Harvest CO2 and sunlight, providing the carbon exudates to the soil ecosystem
• Building soil aggregates and pore spaces, which improves soil infiltration
• Cover the soil, controlling wind and water erosion, soil temperature, and rainfall compaction
• Catch and release of inorganic nutrients, improving water quality
• Salinity management
• Pollinator food and habitat
• Weed suppression
• Wildlife food, habitat, and space
• Livestock integration
• Adding crop diversity
• Adjusting the carbon/nitrogen ratio, to either accelerate or slow decomposition

 

Principle 5: Livestock Integration

Crop residues left on the fields provide many benefits to soil health including increased water infiltration, reduced soil erosion and no cost of the harvest. Incorporating livestock to graze those residues only increases the existing benefits of leaving those residues on the field. Through grazing livestock speed up the degradation process.

Grazing converts high carbon annual crop residue to low carbon organic material, balancing the carbon/nitrogen ratio and managing crop rotation residue for no-till seeding. Grazing also helps to manage weed pressure without the use of herbicides.

Cover cropping combined with livestock grazing can be a very efficient way to build soil organic matter (SOM) and enhance soil biology.[iv]

[i] USDA, Natural Resources Conservation Service North Dakota, Soil Health, retrieved from https://www.nrcs.usda.gov/wps/portal/nrcs/main/nd/soils/health/

[ii] Haddaway, N.R., Hedlund, K., Jackson, L.E. et al. How does tillage intensity affect soil organic carbon? A systematic review. Environ Evid 6, 30 (2017). https://doi.org/10.1186/s13750-017-0108-9

[iii] Richard J, Peukert Manuela, Succurro Antonella, Koprivova Anna, Kopriva Stanislav, The Role of Soil Microorganisms in Plant Mineral Nutrition—Current Knowledge and Future Directions, Frontiers in Plant Science, VOLUME 8, 2017              

[iv] Hewins, D.B., Lyseng, M.P., Schoderbek, D.F. et al. Grazing and climate effects on soil organic carbon concentration and particle-size association in northern grasslands. Sci Rep 8, 1336 (2018)

Cover Crop Strategies

Cover crops slow erosion, improve soil, smother weeds, enhance nutrient and moisture availability, help control many pests and bring a host of other benefits to your farm. At the same time, they can reduce costs, increase profits, and even create new sources of income. You will reap dividends on your cover crop investments for years because their benefits accumulate over the long term. [i]

Some common goals for cover crops are to:

• Provide nitrogen
• Add organic matter
• Sequester carbon dioxide
• Improve soil structure
• Reduce soil erosion
• Provide weed control
• Manage nutrients
• Furnish moisture-conserving mulch

 

Examples of some common uses of cover crops
	N source	Soil builder	Erosion fighter	Weed fighter	Good grazing	Attract beneficials
Warm season	Sweet clover, peas, Cowpeas	Sorghum-Sudan, mustards	Sweet clover, Cowpeas, Sorghum-Sudan	Buckwheat, Sweet clover, Cowpeas	Millet, grazing corn	Buckwheat, sunflower, mustards
Cold season	Clovers, hairy vetch, faba beans	Crimson clover, vetch, rye	Barley, rye, clovers	Berseem clover, rye, oats,	Berseem clover, red clover, annual ryegrass	Hairy vetch, crimson clover, peas

[i] This chapter is based on SARE’s publication: Managing Cover Crops Profitably, ed. Andy Clark, 3^rd ed, June 2012

Building Soil and Tillage

Soil is a complex substance with physical and chemical properties that allow it to sustain living organisms- not just plant roots and earthworms, but hundreds of thousands of different insects, wormlike creatures, and microorganisms. When these organisms are in balance, your soil cycles nutrients efficiently, stores water and drains the excess, and maintains an environment in which plants can thrive.

To recognize that a soil can be healthy, one has only to think of the soil as a living entity. It breathes, it transports and transforms nutrients, it interacts with its environment, and it can even purify itself and grow over time.

Regardless of how healthy or alive your soil is right now; cover crops can play a vital role in ensuring that your soil provides a strong foundation for your farming system. While the most common reasons for including cover crops in a farming system may relate to the immediate short-term need, the continued practice of cover cropping becomes an investment in building healthy soil over the long term.

Erosion control

Erosion of topsoil is common in many farms, depriving fields of the most fertile portion, that containing the highest percentage of organic matter and nutrients. Cover crops can play a major role in fighting soil erosion by:

• Slow the erosion caused by moving water by creating an obstacle course of leaves, stems, and roots through which the water must maneuver on its way downhill.
• Increase the soil’s ability to absorb and hold water, through improvement in pore structure, thereby preventing large quantities of water from moving across the soil surface.
• Help stabilize soil particles in the cover crop root system.

Conservation tillage is a system that leaves enough crop residue on the soil surface after planting to provide 30% soil cover, the amount needed to reduce erosion below tolerance levels.  Conservation tillage aim for greater soil cover also because of additional benefits of crop residue. Cover crops are critical to producing this residue and have the potential to maximise conservation tillage benefits.

 

Organic matter additions

The benefits of organic matter include improved soil structure, increased infiltration and water-holding capacity, increased cation exchange capacity (the ability of the soil to act as a short-term storage bank for positively charged plant nutrients) and more efficient long-term storage of nutrients. Without organic matter soil is just a dead mixture of ground-up and weathered rocks.

Plant materials that are succulent and rich in proteins and sugars will release nutrients rapidly but leave behind little long-term organic matter.

Plant materials that are woodier or more fibrous will release nutrients much more slowly, perhaps even tie up nutrients temporarily, but will promote more stable organic matter, or humus, leading to better soil physical conditions, increased nutrient-holding capacity and higher cation exchange capacity.

Grains and other grasses and nonlegumes will contribute to humus production but will not release nutrients very rapidly or in large quantities if incorporated as they approach maturity.

Perennial legumes such as white and red may fail in both categories – their leaves will break down quickly, but their stems and root systems may become tough and fibrous and can contribute to humus accumulation.

Cover crops can promote good aggregation in the soil through increased production of microbial glues that help to form soil aggerates or “crumbs”. Well-aggregated soils also are less prone to compaction, which has been shown to reduce yields of vegetables such as snap beans, cabbage, and cucumber by 50 percent or more.[i]

 

Nutrient cycling

Cover crops enhance nutrient cycling in your farming system by taking up nutrients that otherwise might leach out of the soil profile. These excess nutrients have the potential to pollute groundwater and streams, not to mention impoverishing the soil they came from.

Furthermore, legumes have a gift of being able to fix atmospheric nitrogen to your soil. Several factors impact the efficiency of this nitrogen fixation and the loss of soil nitrogen by leaching. Of the common plant nutrients, nitrogen in the nitrate form is the most water-soluble and therefore the most vulnerable to leaching. Anytime soil is bare and appreciable rainfall , nitrates are on the move.

The best cover crops to use for nitrate conservation are nonlegumes that form deep, extensive root systems quickly after cash crops are harvested.

Legumes, with the help of rhizobia bacteria, can add nitrogen to enrich your soil. The efficacy of legume’s nitrogen fixation is determined by available rhizobia bacteria, presence of micronutrients like iron, potassium and sulphur, sufficient aeration of the legume roots and the pH suitable for rhizobia.[ii]

A real challenge for farming is to keep as much of the nitrogen as possible in a stable, storable form until it is needed by the crop. The best storage form of nitrogen is the organic form: the undecomposed residue, the humus, or the microorganisms themselves.

Materials with a high carbon to nitrogen (C:N) ratio, such as mature grass cover crops, straw or any fibrous, woody residue, have a low nitrogen content. They can “tie up” soil nitrogen, keeping it immobilised (and unavailable) to crops until the carbon “fuel supply” starts depleting.  Deep rooted perennial grasses are typically good at adding soil organic matter and sequestering atmospheric carbon dioxide.

[i] Wolfe, D. 1997. Soil Compaction: Crop Response & Remediation. Report No. 63. Cornell Univ., Department of Fruit and Vegetable Science, Ithaca, N.Y.

[ii] Ibid.

 

 

Managing Pests

Cover crops play an increasingly important role on farms worldwide. In addition to slowing erosion, improving soil structure, and providing fertility, there is a growing evidence that cover crops can help farmers to manage pests.[i]

Cover crops can reduce insect infestations, diseases, nematodes, and weeds. Applying cover crops help to minimize reliance on pesticides, cutting costs and reducing chemical exposure while protecting the environment and increasing consumer confidence of your products.

New strategies that preserve farm’s natural resources while improving profitability emphasizes a farm as an “agro-ecosystem” – a dynamic relationship of the mineral, biological, weather, and human resources involved in producing crops or livestock.

Environmentally friendly pest management starts with building healthy soils. Crops grown in biologically active soils resist pest pressures better those grown in poor soils. Reducing or eliminating pesticides favours diverse, healthy populations of beneficial soils flora and fauna. Eliminating or reducing tillage that causes losses of soil structure, biological life or organic matter make crops less vulnerable to pest attacks.

Insect management

In natural ecosystems, insect populations are controlled by their natural enemies. Conserving and encouraging beneficial organisms that control pest insects is a key to achieving sustainable pest management.

By including cover crops in your rotations and not spraying insecticides, beneficials often are already in place when you plant spring or summer crops. However, if you fully incorporate cover crops into the soil, you destroy or disperse most of the beneficials that were present. Conservation tillage is a better option because it leaves more of the cover crop residue on the surface.  The goal is to provide year-round food and habitat for beneficials to ensure their presence within or near primary crops.

When crops are attacked by pests, they send chemical signals that attract beneficial insects. The beneficials move in to find their prey. Maximising natural predator-pest interaction is the primary goal of biologically based Integrated Pest Management (IPM), and cover crops can play a leading role.[ii]

Beneficial insects need nectar and pollen to survive and reproduce. For example, adult parasitoid wasps feed on flowers, while the parasitoid larvae prey on pests such as aphids, caterpillars, and stink bugs. Lady beetle, aka ladybugs, feed on flowers, especially during times of prey scarcity. In addition to flowers, cover crops, such as vetch and fava beans, have extra-floral nectarines or spurs at the base of the leaves. These secrete a sugary syrup that attracts beneficial insects, such as syrphid flies to control aphids.

Disease Management

In the field, although plants are exposed to a wide diversity of micro-organisms, plant infection by micro-organisms is rare. A pathogen must cross many plant barriers before it can cause disease to root, stem, or leaves. You can use cover crops to reinforce these barriers.[iii]

Plant cuticle layers which protect the plants against pathogens can be physically damaged by cultivation, spraying or even by the impact of soil splashing raindrops or irrigation. In well-developed minimum till or no-till crop systems with cover crops you may not need cultivation for weed control and you can minimise spraying.

Many benign organisms are present on the leaf and on the stem surface. These biofilms play an important role in plant disease. Cover crops can help this natural protection process work by reducing the need for application of synthetic crop protection materials and by supporting beneficial micro-organism populations.

Soil-borne pathogenic fungi can also negatively impact production of many crops. Implementing non-hosting cover crops on your production, you can reduce plant disease incidence and severity by enhancing natural disease suppression.[iv]

However, in soils with high levels of disease inoculum, it takes time to reduce population levels of soil pathogens using only cover crops. Pathogen suppression with cover crops should be viewed as a long-term strategy which combines disease management with weed suppression, reducing erosion and nitrate leaching, and improving soil structure.[v]

Nematode Management

Most nematodes are not plant parasites, but feed on and interact with many soil-borne micro-organisms, including fungi, bacteria, and protozoa. Damage to the crop from plant-parasitic nematodes results in a breakdown of plant tissue, such as lesions or yellow foliage; retarded growth of cells, seen as stunted growth or shoots; or excessive growth such as root galls, swollen root tips or unnatural root branching.

You can gradually reduce a field’s nematode pest population or limit nematode impact on crops by using specific cover crops. Nematode control tactics involving covers include:

• Manipulating soil structure or soil humus
• Rotating with non-host crops
• Using crops with nematocidal effects, such as brassicas

A study in sugar beets production found that malt barley, radishes and mustard worked as the standard nematicide. Increased production more than offset the cover crop production and lamb grazing increased profit even further. [vi]

Weed Management

Cover crops can be used to smother crops to shade and outcompete weeds.  Cover crops can also serve as a “living mulch” to manage weeds in vegetable production.

Cover crops are left to grow between rows of the cash crop to suppress weeds by blocking light and outcompeting weeds for nutrients and water. They may also provide organic matter, nitrogen and other nutrients mined from underneath the soil surface, beneficial insect habitat, erosion prevention and wind protection.

To avoid competition with the cash crop, living mulches can be chemically or mechanically suppressed. Some cool season cover crops such as crimson clover may die out naturally during summer crop growth in warm climates and do not compete for water or nutrients. However, cover crops that regrow during spring and summer can compete strongly for water with spring planted crop.

A test conducted in Ohio, US, demonstrates how cover crops can successfully replace herbicides in some horticultural production systems. The study demonstrated that a killed mulch of a cover crop mix of rye, hairy vetch, crimson clover, and barley kept processing tomatoes nearly weed-free for six weeks in an Ohio test. Tomato fields kept weed-free for 36 days yield as much as fields kept weed-free all season. [vii]

Cover crops often suppress weeds early, then prevent erosion or supply fertility later in the season. For example, shade-tolerant legumes such as red clover or sweet clover that are planted with spring grains grow rapidly after grain harvest to prevent weeds from dominating fields in late summer.

[i] Snapp, S. et al. 2005. Evaluating cover crops for benefits, costs, and performance within cropping system niches. Agron. J. 97:1-11.

[ii] 420 Tumlinson, J.H., W.J. Lewis and L.E.M. Vet. 1993. How parasitic wasps find their hosts. Sci. American 26:145-154.

[iii] 314 Paxton, J.D. and J. Groth. 1994. Constraints on pathogens attacking plants. Critical Rev. Plant Sci. 13:77-95.

[iv] Magdoff, F. and H. van Es. 2001. Building Soils for Better Crops, 2nd Edition. Sustainable Agriculture Network. Beltsville, MD. www.sare.org/learning-center/bsbc

[v] Vincent V. Michel, Karolis Urba & John Clarkson, Mini-paper – Green Manures and cover crops to reduce the pressure of soil-borne diseases in annual crop, 2020

[vi] Koch, D.W. 1995. Brassica utilization in sugarbeet rotations for biological control of cyst nematode. SARE Project Report #LW91-022. Western Region SARE. Logan, Utah. www.uwyo.edu/Agexpstn/research.pdf

[vii] Creamer, N.G. et al. 1996. A comparison of four processing tomato production systems differing in cover crop and chemical inputs. HortSci. 121:559-568.

Crop Rotations

Finding the cover crops that fit best to your farming system takes careful planning. The same amount of time should be devoted to designing your cover crops as you devote to your cash crops.

Symbiosis can help you to plan your cover crop rotation, that would allow you to take the full advantage of their benefits. Below are some examples of common crop rotations:

Corn rotation

Provision of winter cover, building soil structure and nitrogen management are the major factors to consider when designing crop rotation for corn. Possible cover crops are rye corn, for winter cover and scavenging nitrogen, hairyvetch for spring ground  cover, mulch and nitrogen, red clover for similar benefits but a slightly less nitrogen and spring growth, and berseem clover for several cuttings for high nitrogen green manure.

Vegetable rotation

Periods of one or two months between harvest of early planted spring crops and planting of autumn crops can be filled using fast-growing warm-season cover crops such buckwheat, sweet clover cowpeas, sorghum-sudan grass or another crop suitable to your conditions.

Plant a winter annual cover on fields that would otherwise lie fallow. Oats add lots for biomass and nurse spring-seeded legumes, sorghum-sudan grass hybrid produces deep roots and leafy stalks that die with the first frosts, yellow sweet clover provides green manure, and brassicas and mustards can play a role in pest suppression and nutrient management.

Dry areas cereal-legume rotations

In dry areas, soils’ moisture availability and use by cover crops might be a concern. However, carefully managed, and selected cover crops in their rotations may result in increased soil moisture availability to cash crops. The key is to have flexible rotations that can be modified to capitalise on soil moisture when available while preventing adverse effects on cash crops.

Perennial medics persist due to hard seed (of concern in systems) providing green manure and erosion control, field peas and lentils are shallow-rooted yet produce crops and nitrogen in years of good rainfall.

Livestock and grazing

Among the several ways that cover crops can boost profits, grazing them is one of the most likely ways to provide a positive first-year return.

Where grazing infrastructure is present, even a modest amount of grazing from cover crops will normally pay for seed costs while also providing some soil improvements. Getting early autumn establishment of fast-growing covers such as cereals and/or brassicas (such as turnips, radishes, kale, etc.) can boost your financial return well above the cost of cover crop seeding.

The cost per ton of feed from a grazed cover crop is usually far less than the cost of hay or silage. Cover crops can provide quality grazing when grass pastures are of low quality, such as late autumn when grasses are poor quality or early spring before the grass greens up.

Incorporating cover crops into a pasture programme can provide a sequence of quality forage that can produce excellent animal performance for as much as twelve months a year and eliminate the need for hay or other stored feed.

Integrating livestock with cover crops can be a major plus for long-term soil health. The urine, manure and saliva from grazing animals has been found to stimulate soil biology. This is not surprising given that our soils evolved with herbivores impacting the soil biology. In fact, there is some evidence that grazing cover crops, especially where significant biomass is achieved, may be a very efficient way of building soil organic matter and increasing soil biology.[i]

Wildlife

The best way to manage wildlife is to promote a diverse landscape of native plants. However, a significant portion of land has been converted to introduced forages and crops for livestock and human consumption. Most crop and introduced forage systems are predominantly monocultures and only fulfill one aspect of wildlife habitat for a limited time during the year.

One way to increase plant diversity for the benefit of wildlife in these systems is to plant cover crops. Cover crops can be used to provide food or shelter during a time of year that the primary crop is not present. For instance, brassicas and legumes provide forage for game and wildlife like deer and turkeys.

However, population increases in deer, rabbits and small mammals can lead to crop damage, therefore cover crop management should be considered alongside other land management practices to mitigate potential problems.

[i] Ritchie, M.E.,” Grazing Management, Forage Production and Soil Carbon Dynamics”, Syracuse University, April 2020

 

Seed mixes for healthy soil

Since 2014, Symbiosis has been testing and analysing optimal cover crop mixes, perfecting the art so that the mixes allow to take a full advantage of the benefits of cover crops.

Symbiosis seed mixes are tailored to address the specific resource concerns of the clients. We will create a custom seed mix for you which considers your location, production system, resource concerns and planting schedule.

Nature’s Cycles

Ecological systems have many biogeochemical cycles operating as a part of the system, for instance: the water cycle, the carbon cycle, and the nitrogen cycle. The flow of nutrients that are critical for life – like carbon, nitrogen, oxygen, phosphorus, and sulphur – are a part of a closed system. These chemicals are recycled instead of being lost and replenished unlike the energy, which is an open system.

Soil is the main terrestrial reservoir of nutrients, such as nitrogen and phosphorus, and of organic carbon. Soil can be compared to a giant sponge, that infiltrates water and enhances access to essential nutrients, supporting plants, animals, and humans.[i]

Human activities and modern agriculture have significantly altered Earth’s cycles.  The human mobilisation of carbon, nitrogen, and phosphorus from the Earth’s crust and atmosphere into the environment has increased 36, 9, and 13 times, respectively, compared to geological sources over pre-industrial times. Fossil fuel burning, land-cover change, cement production, and the extraction and production of fertiliser to support agriculture are major causes of these increases. [ii]

Furthermore, losing the Earth’s soil carbon has changed the water cycle, leading to a rise in dangerous hydrological climate extremes: intense storms, floods, heatwaves, droughts, and wildfires.[iii]

However, growing market demand for environmentally friendly products together with the increasing cost of synthetic agricultural inputs have given an incentive for farmers to apply farming techniques to access free nutrients from the biogeochemical cycles.

[i] Walter Jehne, Regenerate Earth, Healthy Soil Australia, 2020

[ii] Schlesinger, W. H., and E. S. Bernhardt, 2013: Biogeochemistry: An Analysis of Global Change, 3rd Edition. Academic Press, 672 pp.

[iii] Walter Jehne, Regenerate Earth, Healthy Soil Australia, 2020

Carbon Cycle

Carbon is the main component of biological compounds as well as a major component of many minerals. The carbon cycle comprises a sequence of events that are key to make Earth capable of sustaining life.

If soils are one of our greatest assets, then carbon is the currency. Storing carbon in the soil is a long-term investment on agricultural productivity.

The Earth’s bread baskets are areas, where nature has built vast soil carbon deposits. Ukraine, New Zealand and the Great Plains in the US, are examples of areas were agriculture has been able to benefit massive soil carbon stocks built by nature.

There are many reasons for a farmer to increase soil carbon stocks in soil. Protecting and increasing soil organic carbon can:

1. Increase soil water holding capacity
2. Protect or increase soil fertility
3. Maintain and increase resilience to climate change
4. Reduce soil erosion
5. When implemented through the conversation of natural ecosystem, reduce habitat conversion

The best way to increase your soil organic carbon (SOC) is to apply agriculture techniques that focus on building soil’s physical health and replenishing organic matter within the soil.

These practices include mulching, cover-cropping, no-tillage, and agroforestry that protect the soil from elements and return carbon and organic matter to the soil. Research indicates that fertilisers and irrigation alone cannot increase yield – when applied in carbon-depleted soils, only 30 percent of fertiliser and irrigated water reach crops.[i]

[i] Lal R., “Soil Carbon dynamics in cropland and rangeland”, Environmental Pollution, 116, 2002, 353-362

Water cycle

Water is a renewable resource that belongs to a gigantic cycle, the hydrological cycle. It is evaporated from the Earth and the sea into the atmosphere. The energy required for evaporation is supplied by the sun. In the atmosphere, water is transported by the wind in the form of vapour, until it finally returns to the Earth in the form of precipitation.[i]

When water is applied to a dry soil, a certain amount will be absorbed or stored before drainage starts. If the storage capacity and drainage rate of the soil is exceeded, then water will either pond on the surface or run off downslope. Available water capacity (AWC) measures the capacity of soil to absorb and store water available for plants. [ii]

In soil with a good structure, the particles of sand and silt are held together in aggregates (small clumps) by clay, humus, and calcium. The large empty spaces between the aggregates (macropores) allow water and air to circulate and plant roots to grow down into the soil. The small empty spaces (micropores) hold the water the plants need. This “ideal” structure is called granular, or crumbly.

You can tap into the nature’s water cycle by improving your soil’s water holding capacity[iii]:

• Optimise the key ratios in between the essential minerals (see symbiosis.co.nz for more information)
• Increase soil organic matter
• When feasible, avoid using heavy equipment
• Use cover crops like Sorghum-Sudan grass to open compacted soils
• Reduce evaporation and improve soil structure with crop rotation (when precipitation is sufficient)
• Apply mulching
• Reduce tillage
• Use tap rooted cover crops for subsoiling

[i] Tan K.H, “Principles of Soil Chemistry”, CRC Press, Fourth Edition, 2011

[ii] McLaren, R.G., and K.C. Cameron, “Soil Science: Sustainable Production and Environmental Protection”, Oxford University Press, 2nd Edition, 1996

[iii] NRCS, “Effects on Soil Water Holding Capacity and Soil Water Retention Resulting from Soil Health Management Practices Implementation – A Review of the Literature Posted to the NRCS Soil Health Website as of 9/2016”, USDA, March 2018

Nitrogen cycle

Plants require large amounts of nitrogen and contain between 1 to6% nitrogen on a dry weight basis. Nitrogen is almost always the nutrient in most demand as plants need it as a primary constituent for amino acids and for chlorophyll molecules, which is responsible for photosynthesis. [i]

Although most of the soil nitrogen is relatively immobile, nitrate is easily leached when water drains thought the soil. Leaching mainly occurs in late autumn, winter, and early spring when water drains through the soil. Undisturbed ecosystems, such as forests, lose truly little nitrogen by leaching, whereas intensively fertilised and irrigated fields and pastures can lose significant amounts of nitrate. [ii]

Optimising natural nitrogen fixing and reducing nitrogen and leaching can reduce significantly farm input costs while having a positive impact on the environment.

You can reduce nitrogen leaching and denitrification by improving your soil structure and using appropriate cover crops[iii]:

• Increase organic matter in soil to reduce nitrogen and phosphorus losses
• Crop rotations with nitrogen fixing legumes
• Prevent nitrogen leaching by applying nitrogen scavenging cover crops
• Promote the growth populations of nitrogen fixing soil organisms
• Reduce tillage

Phosphorus cycle is also of great importance, see www.symbiosis.co.nz for more information.

[i] McLaren, R.G., & K.C. Cameron, “Soil Science: Sustainable Production and Environmental Protection”, Oxford University Press, 2nd Edition, 1996

[ii] Ibid.

[iii] Magdoff F. and Harold Van Es, “Building Soils for Better Crops”, SARE Outreach Publications, Third Edition, 2009

Soil ecosystems

Soil organisms play principal roles in several ecosystem functions. Soil organisms decompose organic compounds, including manure, plant residue, and pesticides, preventing them from entering water and becoming pollutants. They sequester nitrogen and other nutrients that might otherwise enter groundwater, and they fix nitrogen from the atmosphere, making it available to plants.

Many organisms enhance soil aggregation and porosity, thus increasing infiltration and reducing runoff. Soil organisms prey on crop pests and are food for above-ground animals.

Try to use management practices that promote a thriving and diverse population of soil organisms:

• Feed the soil food web with crop residues and organic materials
• Reduce the use of chemical pesticides
• Reduce the use of synthetic fertilisers
• Practice cover cropping and crop rotations
• Minimise soil disturbance
• Integrate livestock or wildlife to enhance soil biology

 

 

Legumes

Legumes prevent erosion, suppress weeds and add organic matter to the soil. One of the main reasons for selecting legumes as cover crops is their ability to fix nitrogen (N) from the atmosphere and add it to the soil.

Faba (tick) beans

Faba beans are the only true bean that can grow and thrive in cool wet soils and are one of the highest nitrogen-fixing grain legumes.

Unlike most legumes, faba beans continue producing nitrogen through grain fill and maturity. Faba beans tiller very well from the axillary buds making regrowth after grazing a benefit. The vigorous taproot of the faba bean can range from 50cm to 130 cm in depth and can provide more overall biomass than spring peas. One downfall of faba beans is that the larger seed size does not always work well in seed mixes.

White clover

White clover can withstand heavy traffic and supplies a food source for pollinators. As a legume, white clover supplies efficient Nitrogen for soil. It is often used as a soil stabiliser in fruit orchards.

White clover is also an important pasture legume, often grown together with perennial grasses. It can provide up to 20% of the crude protein value to a forage.

Even if white clover makes an excellent forage, it carries a moderate bloat risk. Consequently, white clover should consist to a maximum 0% of the available forage.

Balansa clover

Due to the small seed size, comparable to a white clover, balansa requires less kilograms of seed per hectare than many other clovers. When balansa is in the early rosette stage of its life cycle, above ground growth may be limited but it will be utilising its energy to anchor the taproot which has been observed to reach 35cm deep in just 45 days.

Balansa is very tolerant to grazing in the rosette stage, in fact this encourages balansa to tiller more readily. If you are suffering from soybean cyst nematodes, the bonus is that balansa is not a host plant.

Flowering will occur about two weeks later than crimson clover in the spring and can last for about 45 weeks. The flowers can range from white to pink and are extremely attractive to pollinator insects. As balansa matures it produces large hollow stems, making a roller/crimper a viable termination method.

Berseem clover

Berseem clover produces a non-bloating, high quality forage, that’s more palatable than alfalfa. Berseem forage has been observed to maintain a CP content of 28-30% throughout harvesting regiments, which is slightly higher than crimson clover or alfalfa.

Berseem clover has low water requirements and can provide strong biomass recovery after being mowed. A rapidly, consistent stand can be achieved because germination can occur in just 7 days and minimal hard seed counts.

This clover produces flowers which are self-sterile, so reseeding is not a concern. These flowers do provide a great pollen source, which is highly sought after by honeybees.

With good shade tolerance, this species can be utilised for inter-seeding into crop systems or forage mixtures.

Crimson clover

Crimson clovers spring growth can rapidly produce a large amount of biomass. Crimson can grow at lower temperatures better than almost any other clover species. Maturing earlier in the spring than hairy vetch allows this species to reach its maximum N production sooner.

Peak N production occurs during flowering around the middle of May when it is induced by 12 hours of daylight. This species grows great in mixes and fits well into a traditional corn/soybean rotation.

Even if the clover is winter killed, it still can produce a thick mulch that reduces erosion, increases infiltration and has been shown to inhibit small seeded weed species from germinating. If desired, crimson clover can be utilised in a rotation that would allow it to reseed the field. The deep, red blossoms are 2.5 cm in length and are renowned for their beauty and nectar production. The flowers attract many pollinators and some greatly beneficial insects, such as pirate bugs and lady bugs.

 

Lentil

Lentil thrives in cool, dry conditions where they can remain relatively free of disease.

With a shallow rooting structure that does not have the ability to reach subsoil moisture, low water use and supports mycorrhizal fungi, makes lentils an excellent cover in front of cereals or deep rooting crops.

Though not recommended to be grown for production in higher rainfall environments, if excessive moisture is present during the growing season it will delay plant maturity. This will be excellent for producers who want to plant a summer mixture where the mix can continue to grow under ideal conditions.

Lentils are known for their ability to emerge through thick cereal stubble due to their strong seedling vigor. With rapid seed germination, seedlings generally outgrow the threat of insects or disease pressure during establishment. Throughout its life cycle, lentil provides a higher quality forage. Mature lentil straw is much higher in CP, digestibility and palatability when compared to cereal straws.

Red clover

Red Clover is a fast-growing legume, which high crude protein content and good digestibility make it an excellent forage.

Cold tolerance, Nitrogen production and quick establishment are also some of its useful properties. Due to its fast growth, red clover can be used to suppress weeds. Its flowers attract pollinators and beneficial insects.

If red clover is used as a forage for sheep, it is good to bear in mind that red clover produces estrogens which may alter with breeding cycles. Red clover is susceptible to root rots and foliar diseases which often shorten its lifespan.

Lucerne

With its Nitrogen fixing nodules on main tap and lateral roots, Lucerne is known of its ability to render Nitrogen to soil. Lucerne thrives best on a deep permeable soil, so it is not normally the first choice for compacted soils.

Perennial Lucerne varieties go dormant over winter and generally survive well unless heaving, waterlogging, or icing occur.

Lucerne is high in crude protein and it is grown for grazing and hay forage across temperate areas of the world. Lucerne is resilient because it has a large tap root that can reach deep into the soil, accessing both nutrients and water. It is also an excellent choice for weed control.

Peas

Pea’s rapid spring growth can be amazingly effective at suppressing weeds. With a N content of 3-4%, peas produce 150 to 300kg /N/Ha.

The residue breaks down rapidly, releasing the N quickly. Once established pea can withstand heavy frosts but can easily be killed by herbicide at all growth stages.

With no hard seed and ease to kill, peas do not pose any weed threat. Pest cycles can be broken with peas in your rotation and has been documented to be amazingly effective at reducing take-all disease in wheat.

Persian clover

Every aspect of this plant supports its reputation for excellent forage quality. Mature stems are soft, hollow and have thin structural plant cell walls, leading it to be more digestible than red clover or lucerne.

Some common forage tests boast CP 16-21% and IVDMD 63-78%. Not to mention, studies have shown Persian clover to be more palatable than rape, lucerne, fescue, or perennial ryegrass. High productivity during October November provides excellent regrowth potential following grazing or the ability to support two spring hay cuttings.

Given the right circumstances, one could expect Persian clover to naturally reseed and be redistributed by wind/water via its very mobile, light weight, seed pods. Spring flowers are known to also attract flower flies, which larva are a leading predator of aphids.

Linseed

Linseed, also known as common flax or linseed, is a member of the genus Linum in the family Linaceae. It is a food and fibre crop cultivated in cooler regions of the world. Textiles made from flax are known in the Western countries as linen, and traditionally used for bed sheets, underclothes, and table linen.

Flax can be utilized in many small grain and corn rotations as a potential cover crop or fibre/oil crop. Compared to other common crops, overall nutrient demand is lower and little nitrogen is needed. Vegetative growth normally requires 50 days before flowering occurs but after this flowering can last 2-4 weeks.

Flax can be utilised as a green manure if terminated early enough, but take caution if attempting to cut too late as lignin/cellulose content increase with maturity and would hamper decomposition. Nearly 95% of the water flax extracts from the soil is in the top 60 cm to 90 cm because of its shallow root structure.

This species is an excellent companion crop next to other species in an early season mixture. Flax is generally a self-pollinated crop, but pollinating insects are attracted to the various blue/purple colors of the flowers. Because flax is a broadleaf species, most diseases associated with it will not transfer over and cause infection to corn, soybeans, or wheat except for powdery mildew and rhizoctonia after legumes.

Vetch

Vicia sativa is a sprawling annual herb, with hollow, four-sided, hairless to sparsely hairy stems which can reach two metres in maximum length.

The leaves are stipulate, alternate and compound, each made up of 3-8 opposite pairs of linear, lance-shaped, oblong, or wedge-shaped, needle-tipped leaflets up to 35 millimetres long. Each compound leaf ends in a branched tendril.

The pea-like flowers occur in the leaf axils, solitary or in pairs. The flower corolla is 1-3 centimetres long and bright pink purple in colour, more rarely whitish or yellow. The flowers are mostly visited by bumblebees. The fruit is a legume pod up to 6 or 7 centimetres long, which is hairy when new, smooth later, then brown or black when ripe. It contains 4-12 seeds.

Alsike clover

Alsike Clover grows where other clovers do not. It thrives even in heavy clay soil and in areas prone to flooding. Alsike Clover is an efficient Nitrogen fixer and it provides forage for honeybees and other pollinators.

This perennial clover can be mowed back if needed and is suited to cool temperatures but with a lot of sunlight. Alsike Clover grows well in mixtures with grasses but can be toxic for horses, so it is not recommended for pasture.

Caucasian clover

This is a long-lived perennial legume suitable even for acid soils and for soils where Phosphorous availability is limited. Caucasian clover has a good pest and disease resistance and it can tolerate heavy grazing.

As a legume, Caucasian clover fixes nitrogen to soil, but is not particularly good in adding organic matter.

Caucasian clover spreads underground via rhizomes. It has a slow establishment in large quantities, but it may cause bloat in cattle.

Hairy vetch

Hairy vetch is one of the best Nitrogen producers. It is a winter hardy crop, known from its ease of establishment. The vines of hairy vetch can grow over 3.5 metres long, which can cause challenges with wrapping of the plant on the equipment.

Hairy vetch does miracles with the topsoil, creating the illusion of planting in a cloud due to the soil’s looseness. It can be planted together with plants like cereal rye, that allows the hairy vetch to climb up the ryecorn to allow air movement across the soil surface.

Arrotas clover

High protein content, palatability and low bloating risk make Arrotas Clover a great grazing and forage cover crop. It is best adapted to a temperature range of 5-30 Celsius degrees.

Arrotas Clover has a long and vigorous taproot that open soils and its tall stem suits well for weed suppression.

Some of the limitations of Arrotas Clover are low toleration of poorly drained or saline soils and weak dry matter production during winter.

Lotus

Lotus is a perennial legume with tolerance of moderately acidic soils. It makes high nutritive forage for sheep and cattle and it is not known to cause bloating among livestock.

This is an adaptive cover crop which survives in different soils. It fixes Nitrogen to soil and has a deep rooting system. The two subspecies that are commonly used in cover cropping are Lotus Corniculatus and Lotus Pedunculatus.

While lotus is sensitive for overgrazing it can be quite difficult to kill.

Lupins

Lupins are legumes with deep taproots and nitrogen fixing nodules. They are great at producing green manure and opening and aerating soils.

The flowers of blue and yellow lupins attract beneficial insects and enhance pollination.

Lupin poisoning of cattle has been due to quinolizidine alkaloids or their N-oxides. Bitter lupins have more toxins. Sweet lupins have less or none.

Subclover

Subterranean clovers offer a range of low-growing, self-reseeding legumes with high nitrogen contribution and excellent weed suppression. They grow close to the ground, piling up the biomass in a compact layer.

Subclover cultivars are described by their days to maturity, which can vary from 85 days to 130 days. Denser and less viney than hairy vetch, it persists longer as a weed-controlling mulch.

Subclovers thrive in Mediterranean climates of mild, moist winters and dry summers.

Medics

Once established, few other legumes outperform medics in soil-saving, soil-building and-in some systems-forage. Medics earn a place in dryland crop rotations because they provide N while conserving moisture comparable to bare ground fallow.

Quick spring regrowth suppresses early weeds. Good stands of medics in well-drained soil can contribute sufficient residue to build soil organic matter levels.

Green plants, dry plants and burs of burr medic provide good forage, but solid stands can cause bloat in cattle. The burs are concentrated nutrition for winter forage but lower the value of fleece when they become embedded in wool. Annual medics over seeded into row crops or vegetables can be grazed in fall after cash crop harvest.

Sweet clover

There are biennial, summer annual and winter annual species of sweet clover. They are known for their abilities as soil builders, fertility sources, subsoil aerators and erosion preventers.

Sweet clovers produce abundant biomass and moderate amounts of nitrogen. Its taproot branches deep into subsoil layers. It is the most drought resistant of forage legumes, which thrives in temperate regions wherever summers are mild.

Biennial yellow sweet clover can produce over 7 tons of dry matter in its year of establishment. Annual sweet clover is not frost tolerant but can produce up to 10 tons of dry matter over a summer after being over-sown into a grain crop.

Gland clover

This legume is adaptable to a wide range of soil types. It is resistant to red-legged earth mites and aphids and is both suited to low rainfall environments and has moderate tolerance of water logging.

Gland clover is known of its ease of seed production and compatibility with other annual legumes in mixtures.

Gland clover is susceptible to competition from more vigorous species during establishment and needs restricted grazing during flowering.

Strawberry clover

Strawberry clover is known for its ability to establish and persist on wet, saline and alkaline soils. It is a cool-season forage legume with most of the production in late spring and early summer.

As a leguminous and hardy plant, strawberry clover is a beneficial component of natural or organic pasture management and lawn care due to its ability to reduce nitrogen leaching from the soil and out-compete weeds.

Strawberry clover may cause bloat in ruminants. This can be managed with a significant grass component in pasture.

Grasses

Grasses tend to have extensive root systems. Some establish rapidly and can significantly reduce erosion. They are useful for scavenging nutrients, especially Nitrogen, and can produce large amounts of residue. Grass residue is typically low in Nitrogen and high in Carbon.

Sorghum Sudan

Sorghum-Sudan grass hybrids are unrivaled for adding organic matter to worn-out soils. These tall, fast-growing, heat-loving summer annual grasses can smother weeds, suppress some nematode species, and penetrate compacted subsoil if mowed once. Seed cost is modest. Followed by a legume cover crop, Sorghum-Sudan grass hybrids are a top choice for renovating over farmed or compacted fields.

The hybrids are crosses between forage-type sorghums and Sudan grass. Compared with corn, they have less leaf area, more secondary roots and a waxier leaf surface, traits that help them withstand drought. Like corn, they require good fertility -and usually supplemental nitrogen -for best growth. Compared with Sudan grass, these hybrids are taller, coarser, and more productive.

Annual ryegrass

Extending the grazing season while protecting and building the soil is a great benefit of this species.

The biomass nitrogen content can range from 1.3-2.4%, and can vary depending on the amount of residual nitrogen left from the previous crop. Reports of annual ryegrass having the potential to scavenge up to 230kg of residual N/Ha/yr have been recorded.

Ryegrass can be very successfully broadcast into established row crops. Winter killed ryegrass can still provide weed suppression, soil protection and trap residual N until spring.

Ryegrass attracts very few pest insects that could pester the next crop. With lower needed seeding rates per hectare means you will spend less on freight and your applicator can remain in the drill or in the air longer.

Millet

With extremely rapid growth, brown top millet can fill narrow growing windows to produce a nice quality forage. Under ideal conditions seed will germinate within 5 days, and forage or seed will be ready to harvest within two months’ time.

Exceptionally fine stems and leaves allows plant material to dry down effectively for dry hay production. Brown top millet is an effective nurse crop, much like oats, in stabilising erosive hill slopes and providing cover for slower growing target species to become established. Research has shown brown top helps to suppress root-knot nematodes within the soil.

With the ability to easily reseed and that seed to remain viable in the soil profile for years, makes brown top millet an excellent regenerating food plot for wildlife.

Prairie grass

Prairie grass grows vigorously during winter and spring. Prairie grass can be planted when the soil temperature is above 10 degrees Celsius.

With its high protein content and particularly good palatability, prairie grass has high grazing and forage potential.

The limitations of this cover crop have a relatively short lifespan and weak toleration of poorly drained, heavy textured or infertile soils.

Cocksfoot

Cocksfoot is a high yielding perennial grass, capable of producing up to 15,000 KG of dry matter per hectare in ideal conditions. It is great at sequestering atmospheric carbon and building soil organic matter.

Deep roots of cocksfoot species help to hold soil together and reduce erosion, making it also very drought resistant. However, cocksfoot must be regularly grazed, or it becomes coarse and unpalatable.

Cocksfoot has a high tolerance of aluminum and will also grow well in shallow soils. It does not perform well in soils that are prone to waterlogging. Cocksfoot has many subspecies that are suitable in growing in different climates.

Tall fescue

This deep-rooted perennial grass is great at sequestering carbon and building soil organic matter, especially if the grazing system allows long recovery times.

The tall fescue varieties that originate from Europe or America are spring/summer active varieties while those of Mediterranean origin are winter active and summer dormant.

Tall fescue has a high nutritive value comparing favourably to perennial ryegrass, phalaris and cocksfoot.

Perennial brome

Perennial brome grasses are extremely palatable perennial grasses which can produce high-quality herbage throughout the year and a particularly good choice for producing winter forage. Common varieties are Atom, Grasslands Gala and Bareno.

Brome grass is a sod-forming perennial, spreading aggressively underground by rootstocks or rhizomes. It forms a dense sod which is an excellent soil binder and withstands considerable abuse from trampling by livestock.

The profusely branched root system not only holds soil effectively while the grass is growing, but it also adds much organic matter and fibre to the soil, which makes it more resistant to erosion.

Festulolium

Festulolium is a hybrid cross between Festuca and Lolium species. It is mainly utilised in pastures for grazing and stockpiling.

It has higher forage yields than perennial ryegrass, increased mid-summer growth compared to other cool season grasses, high disease resistance, winterhardiness and persistence.

This grass is easy to establish due to its rapid germination and seedling vigor.

Perennial ryegrass

Perennial ryegrass is a highly efficient builder of soil organic matter, due to its belowground productivity. It is a valuable forage and soil stabilisation plant.

Perennial ryegrass establishes easier and more quickly than most of long-lived pasture grass varieties. Under ideal conditions, perennial ryegrass is ready to graze within 60 days of planting.

Perennial ryegrass can also be inter-seeded in existing weak stands of grass with fairly good results. Perennial ryegrass has a wide range of adaptability to soils but thrives best on dark rich soils. It will withstand wet soils with reasonably good surface drainage. It will not tolerate standing water for extended periods of time.

Crested dogstail

Crested Dogstail has traditionally been a grazing grass and can be found in abundance in sheep pastures. Crested dogstail grows well late into the season when other grasses have halted their growth.

The wiry spikelet of crested dogstail is often by-passed by livestock, allowing regular reseeding. Its leafy lower growing leaves are palatable particularly for sheep. Crested dogstail has good cold tolerance and it can stay green long into the winter.

Yorkshire fog

This tufted perennial grass can grow up to 1 metre high. It is very tolerant of waterlogging and has been long used as a valuable fodder grass in the northern hemisphere.

Yorkshire fog can tolerate a wide range of fertility and acidity conditions. Its value for grazing is better when it is still young. Low palatability may result in companion species being overgrazed allowing Yorkshire fog to invade these areas.

Timothy

Timothy is known for its palatability and superior winter hardiness. It has a shallow root system, which makes it unsuitable for droughty soils.

Timothy is used mainly for hay, but also for pasture and silage. It makes an excellent companion grass for alfalfa or clover since it does not compete with legumes. Timothy thrives best on rich, moist bottom lands and on finer textured soils, such as clay loams.

Phalaris

Phalaris is a persistent and productive temperate perennial pasture grass. It is known for its ability to control weed growth and tolerance to extended periods of heavy grazing.

This grass performs good even in waterlogged or poorly drained soils and is very pest and disease resistant.

Phalaris may become dominant in the pasture and exclude all legumes, causing a decline in pasture quality and production. Maintaining grass-legume balance requires good grazing management.

Herbs

Herbs attract beneficial insects and make a great forage for livestock. Mineral rich herbs are known to have a beneficial impact on livestock health and fertility.

Chicory

Chicory prefers loamy and well drained soils. As a forage, Chicory is rich in Potassium, Calcium, Magnesium, Sulphur, Zinc and Sodium. It is a grazing tolerant plant with good drought resistance.

Chicory is one of the first plants to come out from winter dormancy, so it can be used as summer forage. Different species of beneficial insects are attracted to chicory, which makes it an excellent pollinator.

High residues of soil Nitrogen are not recommended for Chicory, as it tends to reduce the accumulation of dry matter in the taproot.

Plantain

Plantain is a low growing broad-leaf forb with good drought and winter hardiness. It has de-worming and antibiotic properties and its dense root system allows good traffic bearing.

High in sugar, plantain is very palatable for livestock. It is often used for erosion control, building soil and for weed suppression.

The seeds of plantain are small, which may cause problems in seeding.

Sheep’s Burnett

Sheep’s Burnett is a deep-rooted perennial herb, which is palatable, and has high levels of protein and Vitamin A.

Deep tap roots help Sheep’s Burnett to remain green on thin and dry soils. It starts to grow early in the spring, has high grazing quality and a long season.

The deep tap roots draws up minerals and elements and stores them in the top layer of the soils; there they are easily available for other plants too.

Borage

Borage is a herb native to the Mediterranean region which attracts beneficial insects. It has biofumigant properties and it is often used to protect brassicas and legumes from pests and diseases.

Borage is a very hardy plant and will thrive in almost any soil. It is technically an annual, however it readily reseeds itself from year to year.

Parsley

Parsley is a herb which belongs to the same family as carrots. It grows deep-green foliage above a long taproot.

Predatory wasps and other beneficial insects are attracted to parsley’s scent and flowers. It can be inter-planted with tomato rows to attract wasps that feed on hornworms. Parsley is often intercropped with asparagus and corn.

Yarrow

Yarrow is a perennial herb which distinctive rhizome enables the plant to survive drought better than most plants. It can be planted to combat erosion.

The flowers of yarrow attract beneficial insects like ladybugs and predatory wasps.

While yarrow is often regarded as a weed, it can be used for grazing and it has decent nutritional value.

Grains

Grains used in cover cropping are winter hardy cereals with extensive soil holding root systems and good weed suppression potential. They absorb unused Nitrogen to soil, thrive in low-fertility soils and cover the ground quickly.

Buckwheat

Buckwheat’s vigorous growth habits make it an exceptional choice for a quick establishing crop with superior weed suppression.

This is your crop if you desire a crop that flowers quickly and for extended periods of time. Flowering can occur in the first three weeks of growth and continue for ten weeks.

These flowers attract a large array of beneficial and pollinator insects. If soil moisture usage is a concern, then buckwheat is a good choice. Buckwheat uses about half as much water as a soybean crop.

Black oats

Black oats are sometimes known as Japanese or bristle oats. They are similar in terms of their appearance to common oats but are larger in size and deeper rooting. They are generally used as a soil improving crop or green manure.

They may be especially useful if brassicas already form an important part of the rotation and subsequently cannot be used as a green manure.

Grazing Corn

Corn has long been utilised as a forage source for livestock, proving to be extremely palatable with high nutritional value.

BMR cultivars only improve the forage quality and it is documented by researchers/farmers to notably increase milk production/productivity. Corn is considered a subtropical crop so it can withstand colder nights, higher elevations and Southern growing regions better than tropical warm season grasses like sorghum, Sudan or sorghum x Sudan species.

Like millets, corn poses no prussic acid risk unlike the other warm season grasses previously listed. Grazing corn is the cheapest way to utilise biomass production and cattle have been observed to naturally balance their diets, not just gorging themselves on the grain.

Cereal Rye (Ryecorn)

Cereal Rye has an excellent fibrous root system that alleviates surface compaction. Rye can be successfully planted later than almost any other cover crop due to its low germination and growth temperature requirements.

Cereal rye is known for being the best cereal crop at retaining residual N. It’s typical for a autumn planted cereal rye crop to scavenge on average 10 to 20kg of N, with cases scavenging in excess of 45kg of N. The vigorous spring growth has successful weed suppression through competition and allelopathic chemicals.

Rye can be terminated in the spring through the alternative methods of rolling, mowing, or crimping after boot stage. Rye will out yield any other cereal crops when planted in droughty, infertile, or sandy soils.

Triticale

Triticale has an excellent fibrous root system which allows it to prevent erosion, scavenge nutrients and build soil structure.

This cover crop is known for its great grazing and forage values. With its high biomass production, Triticale suits well for weed suppression. Triticale is a winter hardy crop that grows well in colder temperatures.

Barley

Barley provides great erosion control and weed suppression and tolerates well in dry conditions and light soil. It has a short growing period and it can produce more biomass in a shorter time than any other cereal crop.

If used as a winter annual, barley develops a deep, fibrous root system. As a spring crop, the root system will be relatively shallow, but it holds soil together well.

Several studies suggest that barley can reduce the risk of leafhoppers, aphids, armyworms, root-know nematodes, and other pests.

Brassica

Brassica and mustard cover crops are known for their rapid autumn growth, great biomass production and nutrient scavenging ability. Most brassica species release chemical compounds that may be toxic to soil borne pathogens and pests.

Tillage radish

Rapid autumn growth in short windows, allows radishes to fit perfectly into a traditional corn and soybean rotation.

Radish residue breaks down very quickly in the spring, leaving a clean seed bed until the end of autumn. The residue has been proven to inhibit small seeded annuals from germinating. Nutrients that were scavenged are readily released back into the soil for the subsequent crop.

A field planted in radishes, will allow the soil to dry and warm faster in the spring. The large root channel left behind is rich in nutrients, allows tremendous water infiltration, reduces water erosion, and a path for crop roots to follow through compacted soil layers. During decomposition, radish bio-fumigates the soil which can reduce pest and nematode populations.

Rape

Rape’s rapid forage growth produces quality pasture equivalent to alfalfa, with a crude protein value around 16-17%. Boasted for its nutrient scavenging abilities, rape can accumulate potentially large amounts of residual N up to 100kg N/Ha.

Also, root exudates secreted by rape are known to aid in turning insoluble P into a more available form.

Adding rape in between wheat crops has been shown to greatly reduce take-all in wheat. Rape has an excellent, deep penetrating taproot with a dense fibrous root mass surrounding the tube.

Yellow Mustard

Mustard produces significantly more glucosinolates than other brassicas, which bio-fumigates the soil during decomposition, proving to be toxic to many soil pathogens and pests.

To best utilize these glucosinolates, mature green vegetation should be turned into the soil. In no-till operations you will still benefit from having this species for this use.

When allowed enough growing season, brown mustard stem residue can remain erect throughout the winter months, aid in capturing snow to help build moisture in the soil profile.

Growing mustard in a potato rotation was observed to increase tuber quality and yields similar to that of chemically fumigated fields. Other documented effects of having mustard in your rotation is suppressing potato early dying and reduced root rot in pea rotations.

Brown Mustard

Mustard residues which contain glucosinolates suppress soil-borne fungi and nematodes. For use as a soil biofumigant, mow mustard crop at flowering stage, but before mature seed set, and incorporate into the soil immediately.

The difference in between brown mustard and yellow mustard is that brown mustard grows more biomass and its glucosinolates are better at suppressing soil pathogens and nematodes.

Strong brown mustard stem residue can remain standing through winter, capturing snow and building moisture in the soil. Brown mustard emerges rapidly after planting and survives well in cool conditions.

Turnip

Sugary Turnip makes good forage for livestock. They are full of protein and suit perfectly for winter grazing. As Turnip survives well in colder temperatures, it can be planted in the late autumn.

The deep roots of turnip open soil for other plants to follow. Turnip can also efficiently use residual Nitrogen and put it back into the soil.

Turnip is high in glucosinolates, which may cause thyroid enlargement for young stock, if fed too long with Turnip. If livestock can graze immature plants, Nitrogen toxicity may also become a problem.

Kale

Kale is a winter hardy cover crop, which tap roots help to break up soil. It can withstand a cold winter and begin growing in the spring as the weather warms.

Kale protects the soil from erosion and tolerates saline soils. It is high in protein and feed value and very palatable for both sheep and cattle. Broad leaves of kale help to smother weed growth.

Swede

This brassica grows well in areas of high rainfall; however, they require well drained soils. With ideal growing conditions, swedes can yield up to 20 tons of dry matter per hectare.

Swedes are one the highest energy forage crops and since they are very frost tolerant, they can provide forage late into the winter and early spring.

Swede grows slowly and it typically requires 150-180 days to reach maturity. It can be used as a pioneer crop or to provide weed control and soil preparation prior to renovating with perennial pasture.

Alyssum

Alyssum makes a great cover crop for weed suppression and for attracting beneficial insects. Its flowers attract predatory wasp species that feed on caterpillars, aphids, and other pest insects.

Alyssum adds carbon to soil, and it is a winter hardy flower that can be set out in early spring. In frost-free climates Alyssum can be also grown throughout the fall and winter.

This cover crop likes a sunny climate but does not tolerate well prolonged dry periods.

Arugula

Arugula (Eruca Sativa) is an overwintering Brassica, which is useful for suppressing weeds and minimising surface compaction. Even though it provides less ground cover that turnips or rape, it has more biofumigant properties.

Arugula has been found to reduce the populations of root knot nematodes when inter-cropped with tomatoes. The arugula attracts nematodes, but they cannot reproduce on its roots, so nematode populations reduce. Arugula acts both as a green manure and a nematode trap crop.

Broadleaf

Broadleaves are commonly used to suppress weeds, build organic matter, improve water infiltration, and create forage for livestock. Their flowers attract beneficial insects and their roots anchor the soil, preventing erosion.

Phacelia

Phacelia scavenges for N in the soil and provides C to build soil organic matter. It can be used for feed or hay in soil with low to medium nitrogen availability.

Great root structure breaks up clay soil. Phacelia is a long day plant, flowering only when days are longer than 13 hours (Nov to Mar). It germinates at temperatures above 2.8 Celsius and winterkills at -8 Celsius.

Great as a pollinator because its vibrant blue flowers attract bees and other insects. A quick growing plant which makes a fine, feathery but dense carpet that shades and holds the soil but allows moisture to trickle through. The extensive root systems create biomass comparable to buckwheat. Fibrous root systems can reach a depth of 75 cm. Phacelia can produce 6-16 tons per hectare of biomass in 14 weeks contributing 37-60 units of N per hectare.

Great for sugar beet nematode control. Can survive temperatures above -6 degree and can grow up to 1.2 metres tall. Its use as an autumn/winter cover crop may be appropriate when it will be followed by a vigorous cash crop in early spring. 

Sunflower

Sunflower is renowned for its extensive and prolific root system and its ability to soak up residual nutrients out of reach for other commonly used covers or crops.

This species can also take advantage of short growing seasons in case of damaging hail or poor emergence to cash crops.

If planning to harvest for oil or seed or simply to attract birds, sunflowers have remarkably similar planting and harvesting methods to that of corn. Because insects are attracted to the bright colours of sunflower heads, pollinators and beneficials such as bees, damsel bugs, lacewings, hoverflies, minute pirate bugs, and non-stinging parasitoid wasps are often found in fields of sunflower and in following crops.

Sunflowers also work very well in cover crop cocktails/mixtures. With rapid early season establishment, additional covers under the canopy that normally do not grow under cool conditions can begin to take advantage of warmer and favourable weather when sunflowers are growing slower.

With upright growth and anchored plants in the soil, surrounding vining/climbing cover crop plants can support their own growth by working their way up to reach sunlight thereby providing the structure they need to grow. Because sunflowers can add significant biomass production in just a short growing season, they can also serve as additional forage or silage for livestock fees.

Safflower

This warm season broadleaf has a deep taproot, which can break hard soil, enhancing water and air movement in the soil structure. It is suited perfectly for cereal crop rotation, as it is successful at breaking many plant diseases.

Growing safflower may reduce pest pressure while attracting beneficial insects. It has good grazing and forage potential, even though its’ spines can cause palatability issues when mature.

Safflower is also a very efficient nitrogen scavenger that supports mycorrhizal growth.

Chenopodium

Chenopodium are numerous species of perennial and annual herbaceous flowering plants known as the goosefoots. They belong to a family of Amaranthaceaa. Fat hen can be interseeded as a trap crop while quinoa and chia are protein rich super foods with flowers that attract beneficial insects.

Quinoa

Quinoa is a fast-growing crop, ready to harvest after 4-5 months from planting. This protein rich broad leaf may face competition from weeds especially during the first two to three weeks.

Quinoa thrives in cooler weather and due to its’ deep taproots, it is extremely drought tolerant. As it originates from the Andean mountains, it can tolerate high levels of salt, wind, and frost.

Ideally plant quinoa to loose, sandy soil with a pH level from 6.0 to 8.5. Some growers have found that it is suited well to a crop rotation with grasses. Quinoa is prone to several fungal diseases, that is why good drainage is important. Quinoa flowers also attract beneficial insects.

Depending on the variety, optimal growing conditions are in cool climates with temperatures that vary between −4 °C during the night to near 35 °C during the day. Due to its high demand, this superfood has faced supply shortages in the past years, making it also an attractive cash crop

Lamb’s quarter (fat hen)

This Chenopodium is often considered to be a weed but in many regions it is cultivated as a grain or vegetable crop as well as animal feed.

Lamb’s quarter prefers nitrogen rich soils where it grows particularly fast. Lamb’s quarters are vulnerable to leaf miners, which makes it a useful trap crop for cash crop interseeding. It attracts leaf miners which might otherwise have attacked the cash crop.

Also known as fat hen, it is used as feed for chickens. Cattle and sheep may accumulate toxic levels of nitrate if their feed contains too much of lamb’s quarters.

Chia

Chia is a highly nutritious Chenopodium originally from central America. The flowers of chia seed attract bees and other beneficials and it performs very well as a weed-suppressing cover crop.

Chia prefers well-drained soils of light to medium texture. It is not particular with respect to soil pH, but it does require a sunny location. The demand for healthy foods is increasing the prices for Chia, making it also an interesting cash crop.