Section C: Organic Agriculture in the Agroecoystem

Projected outcomes:

  1. Students will begin to apply ecological analysis to organic production systems.
  2. Students will learn about some key organic practices for both crop and livestock production.
  3. Students will learn how to get technical information about organic agriculture.

Background /Lessons:


Organic production. A production system that is managed in accordance with the Act and regulations in this part to respond to site-specific conditions by integrating cultural, biological, and mechanical practices that foster cycling of resources, promote ecological balance, and conserve biodiversity.

From the definitions section of the National Organic Standards, Electronic Code of Federal Regulations (e-CFR), Title 7: Agriculture, Part 205. Accessed December 2006.
See also expanded definition by the National Organic Standards Board

Like natural ecosystems, agro-ecosystems are characterized by nutrient flows and cycles, energy flows, and the interactions of living organisms with each other and the physical environment. However, agro-ecosystems differ from natural ecosystems in two key ways:

  • First, we expect them to export particular biological goods for our use.
  • Second, we deliberately manipulate them to get them to produce those goods in abundance.

These two special qualities of agro-ecosystems in turn affect their key ecological processes. As the definitions above show, organic agriculture seeks to work with ecosystem processes to achieve its production goals. Because crops and sites and farming systems are so variable it is a major challenge to create organic standards that meet the ecological goals and are still workable for farmers.

This section begins with a quick look at the role of the soil in the organic agro-ecosystem and then encourages students to think about the ecology of organic production by posing four ecological questions.

  1. What are the water and nutrient flows in the system?
  2. What are the sources and sinks of pollutants in the system?
  3. What are the interactions of living organisms in the system?
  4. What are the energy flows in the system?

The Ground Beneath Our Feet

“Organic and low-input farmers pay attention to their soils. In one interview after another, the first thing farmers talked about was how they managed soils.”
From The Real Dirt: Farmers Tell about Organic and Low-Input Practices in the Northeast, 2nd edition, edited by Miranda Smith and Elizabeth Henderson, Northeast Organic Farming Association and Northeast SARE, Burlington, VT, 1998.

Look at almost any text about organic farming, and soil management will be a dominant theme. All farmers value their soil (though they may feel forced to abuse it), but organic farmers are particularly passionate.

One way to look at soils is as a physical medium. It needs to serve a variety of mechanical functions: provide a substrate for plant roots to grow in, allow water to drain so plant roots have access to oxygen, but hold on to enough water that roots have access to water. The soil is also where plant nutrients are stored, transferred to roots, and sometimes lost.

Organic farmers also think about soils as a living system. They value the mechanical functions of soil, but they look beyond those properties to biological and ecological services. Organic standards seek to build and maintain good soil health, rather than simply avoiding damaging the physical structure of the soil.
See Module II, Section C and the Soil Ecology Powerpoint Presentation (Microsoft PPT) or (Adobe PDF) for a brief introduction to soil biology.

The producer must select and implement tillage and cultivation practices that maintain or improve the physical, chemical, and biological condition of soil and minimize soil erosion. Section 205.203(a) of the USDA organic regulations.

Since the 1980s one of the main advances in protecting agricultural soils has been the development of minimum-till and no-till systems for growing crops. No-till systems can significantly reduce both erosion and fuel consumption associated with tillage, but they almost always rely on herbicides for weed control. Because the use of synthetic herbicides is prohibited in organic agriculture, organic farmers face special challenges in trying to control weeds and minimize erosion at the same time.

However, there are a number of practices organic farmers use to minimize erosion and improve soil quality while managing pests, including:

  • conservation tillage (including ridge-till and zone-till)
  • cover crops
  • conservation of crop residues
  • mulching
  • extended crop rotations including perennial crops and small grains
  • strip cropping
  • application of compost and manure

These multiple strategies may be at least as effective as no-till in preventing soil erosion and improving soil quality. To date there has been little research directly assessing the impact of organic agriculture on soil conservation and quality. The Organic Center and the Agricultural Research Service have embarked on a two year study to assess soil quality in organic agriculture

In addition, some organic farmers are beginning to experiment with no-till in at least part of their rotation. For example, one organic dairy farm in Wisconsin planted no-till soybeans (Jodi, link to Miller Farm pdf) into a standing rye cover crop in 2006. The rye was killed when the planter went over the field, weed control was good over most of the field, and yield was 44 bushels/acre. This yield is about 15% lower than the 52 bushels/acre soybean yield from similar fields on the same farm, using normal tillage practices. However, the farmers think they can probably improve yields as they gain experience with managing organic no-till, and they plan to increase their no-till soybean acreage in 2007.

Activity 1: Soil building practices

For more information on soil conservation in organic production see

Ecological question 1: What are the nutrient and water flows in the system?

In a sustainable system, nutrients will be recycled to the extent possible and obtained from renewable sources.

Organic standards encourage nutrient cycling and use of nutrients from renewable sources by:

  • requiring producers to manage soil fertility through use of rotations, cover crops, and the application of plant and animal materials. Section 205.203(b) of the USDA organic regulations.
  • prohibiting use of many fertilizers derived from non-renewable sources, including synthetic nitrogen (anhydrous ammonia, urea) and superphosphate

Most organic farmers in Iowa and Wisconsin rely primarily on green manure crops, local animal manure, and compost to replace nutrients lost by the removal of harvested crops. And good certifiers will seek to ensure that an organic farm’s nutrient management plan will emphasize on-site cycling of nutrients. However, the standards do allow use of some non-renewable fertilizers, such as rock phosphates. In addition, plant and animal-based fertilizers are not necessarily sustainable. For example, manure can be applied in such a way that it pollutes. Or materials such as seaweed could be harvested in an unsustainable manner for use as fertilizer. Thus, how the certifier and farmer interpret the requirement to “promote ecological balance” can influence the sustainability of nutrient management on organic farms.

Conventional farmers and researchers think about providing nutrients directly to the plants. Organic farmers and researchers think of building up healthy and fertile soils, which will then take care of the plants. To date, relatively little research has been done based on the organic paradigm. One interesting organic paradox is that in established organic fields, crops often attain higher yields than would be predicted for conventional systems based on the same available nitrogen levels. A number of organic soil amendments and supplements have not been tested by university researchers. This does not necessarily mean these products are not effective, but marketing claims should be treated with caution.

Activity 2: How will you feed your crop?

Organic standards strongly encourage the use of compost, and they also have strict criteria for the production of compost. For more information on compost see the discussion and associated activities in Module IV, Section C and Cornell’s Composting in Schools website. These materials cover composting in general. Refer to the organic standards in the How will you feed your crop? worksheet for specific requirements for organic composting.

For an overview of manure and compost use in organic agriculture see ATTRA publication Manures for Organic Crop Production.

Organic standards do not directly address use and cycling of water. However, organic farmers often observe that as their soil quality increases under organic management, the ability of their fields to absorb rainfall and retain moisture during droughty conditions increases significantly.

Ecological question 2: What are the sources and sinks of pollutants in the system?

(c) The producer must manage plant and animal materials to maintain or improve soil organic matter content in a manner that does not contribute to contamination of crops, soil, or water by plant nutrients, pathogenic organisms, heavy metals, or residues of prohibited substances.
Section 205.203(c) of the USDA organic regulations.

A sustainable system will minimize the amount of pollutants introduced into the environment.

What is a pollutant? It is a chemical that is damaging to human health or the environment. Just as a weed is a “plant out of place,” so whether something is a pollutant depends in part on context. For example, soil particles are a valuable resource in the crop field. However, if those same soil particles are carried from the field to a stream or river by erosion, they become sediment—a pollutant that can severely damage aquatic communities.

Activity 3: Resource or Pollutant

Although the sources of many agricultural pollutants, such as synthetic fertilizers and pesticides, are prohibited in organic agriculture, allowed inputs can also be pollution sources. For example, soil or manure turn into pollutants when mismanaged and displaced. A sink is where the pollutant winds up. Surface waters, including rivers, lakes, and the ocean, are a common sink for agricultural pollutants.

Organic standards are designed to minimize the risk of pollution, but regulations alone cannot prevent pollution. Good management is required to implement the practices appropriately, and sometimes unpredictable weather can cause even well-managed agroecosystems to result in some pollution.

The best-known aspect of organic agriculture is that it prohibits the use of synthetic pesticides and fertilizers. What is a synthetic pesticide or fertilizer? A synthetic product is one that has been created by some kind of human manipulation and is not otherwise found in nature.

Are all natural pesticides and fertilizers allowed? In fact, many natural products are also prohibited. For example, arsenic occurs naturally and was historically used as a fungicide, but its use is prohibited in organic agriculture. The National List of Allowed and Prohibited Substances sets forth in general terms the prohibited materials that cannot be used; those that are allowed; and restricted materials that may be used in limited circumstances. However, agricultural inputs are often sold under brand names that do not make it easy for farmers to know what the exact ingredients are. In addition, many products contain so-called inert ingredients that they do not have to specify on the label. In order to help farmers and certifiers identify which products meet organic standards, the Organic Materials Review Institute (OMRI), a non-profit organization, reviews products on the markets and certifies them as Acceptable or Restricted, if they can be used in organic production. Unfortunately, there are more products on the market than have been reviewed by OMRI, so there are probably products in the market that would qualify as organic but are not included in the OMRI list.

Activity 4: Check it out!

Soil Management: National Organic Program Regulations published by ATTRA provides an overview of practices organic farmers can use to meet the requirements of Section 205.203 (a) through (d) of the USDA organic regulations.

Ecological question 3: What are the interactions of living organisms in the system?

Sustainable agro-ecosystems will try to work with species interactions and will favor species diversity.

Everything in an ecosystem affects other parts of the ecosystem. Typically, production agriculture has focused on the negative impacts of organisms other than the crop. In this worldview, all non-crop plants are seen as weeds that compete for water, nutrients, and sunlight, and all non-crop animals from insects to birds and mammals are seen as useless at best and crop-destroying pests or disease carriers at worst.

There is some truth to this outlook. Weeds do compete with crop plants, and many types of animals eat parts of the crop and can cause substantial yield losses. Agro-ecosystems differ from natural ecosystems in that we require them to export a good portion of their production for off-site human consumption. So we cannot afford to give weeds, crop predators, and diseases a free hand.

On the other hand, it turns out that many non-crop organisms benefit crop production in a variety of ways, such as by improving nutrient cycling and availability to the crop, eating crop pests, providing habitat for beneficial species, and reducing disease. Organic practices such as crop rotation, cover cropping, planting trap crops, and encouraging beneficial insects use biological diversity to support the farm

Organic agriculture now goes further and requires farmers to protect and increase biodiversity on their farms, even in ways that do not contribute to crop production. However, implementation of this requirement is still evolving. The Wild Farm Alliance has developed guides to help farmers and certifiers improve biodiversity at Recommended practices include

  • identifying critical habitats such as riparian areas and wetlands, wildlife corridors, native grasslands, hedgerows, etc. on the farm map
  • identifying areas of concern such as invasive species and erosion
  • managing water use to benefit wildlife as well as crop production
  • preserving and restoring native habitat
  • scheduling farming practices to benefit wildlife (for example, timing haying to allow ground-nesting birds to fledge)
  • managing predation by non-lethal means such as use of guard animals

Activity 5: take stock

Ecological question 4: What are the energy flows in the system?

In the past two hundred years, our agriculture has made tremendous gains in the amount of food produced per hour of human labor. In large part, these gains have been made by substituting energy from fossil fuel for energy from human work. On average in the US it takes about 2 kcal of fossil fuel to bring 1 kcal of food energy to harvest (in general grain crops have a positive energy balance, vegetable crops are roughly neutral, and meat products have a negative energy balance).

As we begin to recognize the problems caused by releasing CO2 into the atmosphere, and as the cost of fossil fuels begins to rise, agriculture is faced with the challenge of improving fossil fuel energy efficiency without unacceptable increases in labor and cost. To what extent can organic farming contribute to this challenge?

At present, the standards for organic agriculture do not address energy use directly. Like conventional farmers, organic farmers use fossil fuels to power their tractors and other farm machinery. However, there is one big difference in energy use between organic and conventional agriculture: organic agriculture prohibits the use of synthetic nitrogen fertilizer, which accounts for roughly 20 to 30 percent of the fossil fuel energy input for many crops.

There are other differences between organic and conventional agriculture that have energy use implications, but it is not clear whether overall they add up to energy savings for the organic or conventional system. For example, organic agriculture does not use synthetic pesticides, which account for a little over 10 percent of the fossil fuel energy used to produce conventional corn. On the other hand, organic farmers often manage weeds with added cultivation and other practices that consume fossil fuels, such as flame weeding.

Like conventional farmers, organic farmers can reduce their consumption of fossil energy by

  • Recycling nutrients and resources on the farm
  • Minimizing transportation costs by using feed on-farm or selling to and buying from local sources
  • Choosing energy-efficient equipment and buildings
  • Allowing animals to graze (including strip-grazing of standing crops) to avoid energy use involved in harvesting, drying, and storing feed crops. In fact, if the crop will be used to feed livestock, consider switching from row crops to pasture. (See energy data from the Wisconsin Cropping Systems Trials, especially Table 3.)
  • Using renewable energy sources such as wind, solar, or biomass-fueled power

More than half of the energy in our food system is used not on the farm, but in transportation, processing, storage and packaging, and home cooking. Organic agriculture does not offer any energy efficiencies in this important area.

Sustainable practices for the organic consumer

  • Buy local foods, when possible
  • Avoid excess packaging
  • Use energy-efficient appliances and techniques when possible and minimize car travel
  • Use renewable energy sources, if possible (solar and wind power)
  • Consider eating lower on the food chain or sticking to grass-fed meat and dairy products. (Most of the food energy contained in grain is used by livestock to sustain their own life and only a small amount is stored as meat. Thus it takes 4 lbs of corn to produce 1 lb of pork and 10 lbs of corn to produce 1 lb of beef)

For more information on energy see Impacts of Organic Farming on the Efficiency of Energy Use in Agriculture.


Organic standards are designed to promote the ecological sustainability of agriculture, with particular emphasis on soil and water quality, and increasing attention to natural habitat preservation. The requirements of organic agriculture go far beyond a prohibition on pesticide use.

There are two agro-ecological issues, however, that the current organic standards do not address explicitly: quantity of water use and energy use. Many organic farms are highly efficient in both energy and water use, but that is a result of the farmer’s personal values rather than a requirement of the standards.

As the organic standards continue to evolve, perhaps these important ecological concerns will be addressed more directly.