BROADCASTER ARCHIVES

Soil Health and Biodiversity in Practice:
Harnessing biology, ecology and resiliency on the farm.
By Atina Diffley

This article was first printed in the April 2007 issue of the Organic Broadcaster, published by the Midwest Organic and Sustainable Education Service.

I once read that you aren’t really an organic farmer until you can think about pest species before bed and not lose sleep. That single sentence cost me as much sleep as the pests! I struggled with a mental battle between pest and crop for a long time before I began to understand biological diversity.

A healthy farm reflects a diverse ecosystem. To be a successful and sustainable organic farmer, it is important to develop and promote a biologically diverse system that includes all forms of life – from bacteria to fungi to trees and grasses to insects and mammals. All parts of the life cycle are closely interconnected, all equally important.

A metaphor I like to use to image organic farming systems is a spinning jump rope. The spinning rope represents all the forms of life, the communities and ecosystems; the evolutionary processes of interconnected multiple species.

The organic farmer’s goal is to jump a cash crop into this spinning rope of life without knocking the rope down. To develop a system design that keeps the rope spinning smoothly.

Conventional farmers often asked me what we use for a particular pest or disease. They tell me their greatest fear in transitioning to organic is giving up their “protection”. At this point in my farming experience, biological diversity has become deep-rooted in me as our crop “protection”. I feel as much terror at the thought of damaging our bio-diversity as a conventional farmer does at the thought of not being able to use their familiar inputs.

Management decisions farmers make, such as providing habitat and wildlife linkages, tillage and fertility practices dramatically affect biodiversity levels. The very act of putting land into agricultural use limits gene flow among populations and fragments habitats available to any particular species. The closer a farm system is to a native ecosystem the higher the number of species.

Manage farmland as one part of a larger watershed or ecosystem. To my knowledge, humans and a few well-trained dogs are the only species that recognize and respect the Jeffersonian grid. Most species don’t recognize legal boundaries. What habits can you provide that will create links in the larger ecosystem of your area?

Look at an aerial map of your area (available from your county). Map out what presently exists as biodiversity habitat; woodlands, un-mowed grass, hedge rows, wild flowers, waterways, ponds, refuge strips, wetlands AND cropland that you have in soil building crops, especially perennial sods.

Lay out your production areas with the preexisting topography and natural resources as guidelines. Maintain and restore wildlife corridors. Avoid conversion of sensitive habitats to agricultural production. Conduct restoration based on native species and ecosystems. Create field breaks with perennial vegetation.

I think of organic system design as a pyramid of three levels with a base of biodiversity and soil health. All systems and practices designed to create the base goal.

The first and most important level of the pyramid happens before the season begins through planting time: system management. This is your plan to build the internal strengths of your organic system. Soil building, crop rotation, biodiversity habitat, record keeping, soil and water conservation, are all part of a healthy system design. Creating healthy soil and biodiversity creates the conditions for healthy plants. Providing biodiversity habitat for beneficial insects increases ecological pest control.

The second level is post-planting planned management. These are practices that reduce crop stress and optimize quality and yield. Examples: cultivation, irrigation, spacing.

The tip, and smallest part of the pyramid is reactive management. This is where off-farm inputs come in. As systems increases in biodiversity and soil health the need for off farm inputs generally decreases.

Healthy soil is biologically diverse, alive soil. Without sufficient biological life a downward spiral of soil degradation begins. Intensive tillage and insufficient soil building decrease organic matter (OM) and soil biodiversity. Loss of OM and biological life cause soil aggregates to break down and soil surface becomes compacted. Erosion by wind and water increase and more OM and microbial life is lost. Soil water storage and nutrients for plants are reduced and crop yields / quality declines.

Reverse the picture and it is rosy indeed. Increase OM in the soil and biological activity, diversity and nutrient cycling increase. Biological activity increases aggregation, which improves pore structure and tilth. Healthy hydrology increases, providing both better drainage and increased water holding capacity. In initial phases of residue decomposition, bacteria and fungi hold soluble nutrients like N, reducing leaching. Protozoa, nematodes and other larger organisms feeding on the bacteria and fungi gradually release N, P, K and other nutrients, as the plant needs them. All these biological benefits contribute to healthy plants with increased pest and disease resistance. A beautiful soil food web dance.

One of the most important groups of soil fungi, the mycorrhizae, grow within plant root tissues and extend filaments some distance into the surrounding soil expanding the volume of soil from which plant roots can absorb moisture and nutrients. Research has shown increased yields of 50% in peppers with healthy levels of mycorrhizae. Keeping the soil covered, over winter cover and sod crops increase levels of mycorrhizae. Tillage, brassicas, buckwheat, beets and spinach reduces.

It is important to remember that soil OM includes ALL of the organic substances in or on the soil.

• Living organisms: bacteria, fungi, nematodes, protozoa, earthworms, arthropods, and living roots.
• Fresh: dead plant, animal and other organic substances that have only recently been added to the soil.
• Decomposing matter.
• Humus: Organic matter that few soil organisms can decompose.

Fortunately we have the tools to build soil OM and biological life. Soil building crops, reducing tillage intensity, including sod crops in rotation, reducing erosion, increasing utilization of crop residue, adding manures, compost and other organic materials increase the percent of OM.

Think of compost not as a fertilizer, but as sheer life force – a biological inoculant. Used as the sole source of fertility it can lead to nutrient imbalances. In moderation with soil building crops it creates a living, healthy soil.

As nature’s original soil building crop, weeds can be managed as a valuable tool rather then the enemy. The goal is management not annihilation. Huge biodiversity available and the seeds are free. Just don’t let them reseed or compete with your cash crop!

Plant rotation in fields (cash crop, weed and soil building) is an important component of biodiversity. Different species have different nutrient needs, different pests, and support different species both above and belowground. Different rooting structures source different nutrients from the soil – which brings more diversity of nutrients into the nutrient cycling as the plants decompose.

Rotation is not a recipe. Stay flexible and respect weather conditions. A few helpful guidelines include: A MINIMUM of three different crops over seven consecutive years. Plant a deep-rooted crop as part of the rotation. Grow some crops that leave a significant amount of residue. Including cover, catch, sod and green manure crops helps restore fungus damaged by tillage. Don’t follow a crop with another closely related species.

Tillage increases the breakdown of OM matter and affects biological life. It is an important area to have conscious systems. Optimum tillage systems for any farm adjust for soils and climate as well as the need for mechanical weed control, lessening compaction and incorporation of cover crops and compost. Tillage system should favor those that leave residue and mulches on the surface and that limit the pulverization of soil aggregates. Although a fine seedbed is tempting, the damage done to aggregation and healthy fungus needs to be kept in balance. Use it, don’t abuse it!

And everyone’s favorite topic: INSECTS! The majority of insects are not pests. Many are of benefit to humans and the environment.

Bees, moths, beetles, flies and other insects pollinate crops and wild plants. Predacious and parasitic insects are important natural predators of pest species. Insects are extremely important in the breakdown of dead plant and animal material and the recycling of nutrients from these materials. They also supply a dietary component of many types of animals, including other insects, fish, amphibians, reptiles, birds and mammals.

Organic systems of ecological pest management are based on system practices. Off-farm pesticide inputs are a reactive solution of last resort. Before you spray be sure the insect damage is of economic concern. Allowing some pest insects in crops will attract beneficial insects. Avoid use of non-selective pesticides.

All species, including all types of pest, have natural enemies. Take advantage of nature’s insect ecosystem services. Study the life cycle and needs of both pest and beneficial insects.

To increase beneficial insect biodiversity provide food and diverse habitat. Some species need pollen or nectar to reproduce. Manage over wintering environments. Cut up fields with biodiversity strips of grasses and flowers.

Trap cropping and row covers can be a valuable pest control tool while limiting damage to beneficial insects.

The end result? Optimal crop yield and quality with high positive and low negative environmental effects.

A few books which are excellent resources and downloadable free from SARE.
"Building Soils for Better Crops" (available for sale by the MOSES Bookstore.)
"Managing Cover Crops Profitably" (available for sale by the MOSES Bookstore.)
"Manage Insects on Your Farm: A Guide to Ecological Strategies"

Atina Diffley farms at the Gardens of Eagan, a fifth generation family farm, just south of the Twin Cities in MN. For news about exciting changes at GOE, see their webpage at  www.gardensofeagan.com.