A Guide to Sustainable Agriculture

In a time when the majority of our food is produced with large inputs of fossil fuels, synthetic fertilizers, and pesticides, it is heartening to know that more sustainable methods of agriculture do exist and are practiced at farms all over the country. For consumers who are becoming more interested in where their food comes from and how it was grown, this guide gives a behind-the-scenes look at sustainable production systems.

Although there is no single definition of sustainable agriculture, it can be described as a food production and marketing system with the following characteristics:

In practice, a sustainable and profitable farm can take many forms. The following farming methods and management strategies are common on many sustainable farms throughout the US.

Soil Conservation and Improvement	Water Conservation and Water Quality
Alternative Pest Management	Sustainable Livestock and Poultry Production
Markets and Profitability	Sustainable Weed Management Strategies

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Soil Conservation and Improvement

Cover crops: Instead of leaving the ground exposed between plantings, and vulnerable to wind and water erosion (a major problem in the US), farmers plant cover crops, whose roots hold down the soil, as well as controlling weeds and reducing soil compaction. When cover crops are turned under, they add nutrients and organic matter to the soil (this is also called 'green manure'.) Common cover crops include legumes such as clover and alfalfa, which fix nitrogen, an important nutrient for many commercial crops.

Green manures: A crop that is grown in order to be turned under and incorporated into the soil for soil enrichment.

Living mulches: Living mulches are cover crops planted together with the main crop, for the purpose of reducing weeds, increasing nutrients, and preventing erosion.

Mulching: Mulch is a layer of organic or inorganic material applied to fields around plants to suppress weeds, prevent soil moisture from evaporating, and moderate soil temperatures. Common mulches include straw or plastic sheeting.

Crop residue left on fields: Crop residues, such as corn stalks, are left on the surface of the field after harvest and eventually decompose to become valuable organic matter.

Conservation tillage: Conservation tillage is a method of cultivation where there is no tilling or minimal tilling and crop residues are left on the ground. The main purpose is to prevent the soil erosion that often occurs when soil is disturbed during tilling. The organic matter from crop residues also improves soil.

On-Farm Composting: Composting is the breakdown of organic matter into a usable form of soil fertilizer. Compost on a farm can come from manure, bedding material, or crop waste. Composting reduces the need to purchase outside inputs and can even become an additional source of income if there is excess compost that can be sold to nearby garden centers and other buyers.

 

Water Conservation and Water Quality

Efficient Irrigation: Drip irrigation is an example of more efficient water delivery. A system of tubing drips water at the root zone, where it can be absorbed before evaporating. Water waste is minimized, there are fewer weeds since water is distributed only where needed, and there is less nutrient runoff that can result from large applications of water. Irrigation sprinklers are an example of a less efficient type of irrigation, although they are generally less expensive than drip irrigation.

Improving the water-holding capacity of soil: Adding organic matter to soil (by mulching, using green manures, spreading compost, etc) improves the ability of sandy soils to retain moisture and creates air space in dense clay soils, preventing waterlogging.

Growing crops adapted to the amount of rainfall received: Selecting drought-tolerant varieties can be an important water management strategy, as is avoiding planting water-hungry crops (such as alfalfa) in dry regions where excessive irrigation would be required.

Buffer zones: Native vegetation planted on the edges of rivers or surrounding fields acts as a buffer zone between agricultural fields and bodies of water, helping protect water resources by filtering contaminants from farm runoff. Added benefits include providing habitat for a variety of species, including beneficial insects and pollinators, and reducing erosion caused by wind and water.

 

Alternative Pest Management

Biointensive Integrated Pest Management (IPM): IPM is an alternative to the heavy use of synthetic pesticides, which are harmful to the health of farm workers and consumers, use large amounts of energy to produce, and often result in pests developing resistance to pesticides. IPM is an ecology-based strategy utilizing the knowledge of pest interactions with other species and the environment.

Agricultural areas are viewed as part of the overall ecosystem and practitioners aim to support a balance in the system rather than wiping out an entire species from the area. This effort usually involves taking steps to boost the populations of natural pest predators. It also acknowledges that the existence of a pest does not necessarily mean it is significantly harming crops; the goal is to keep pest populations within acceptable limits. Regular monitoring helps growers assess pest populations. IPM does not mean that no pesticides are used, but that some pesticides may be used as a last resort, in combination with other strategies such as designing the agricultural system with habitats for beneficial organisms, rotating crops, and choosing pest-resistant cultivars.

Crop Diversity: Monocrops (large swaths of land occupied by a single crop) encourage pest outbreaks since the insect is surrounded by its favorite food and does not have to travel far to reach its next food source. In contrast, a higher diversity of plants builds overall resistance to pest outbreaks because pests have more difficulty locating their favored food and find it more difficult to locate mates.

Trap Crops: A trap crop is grown to attract insect pests away from the main cash crop. The trap crop is often removed once the pest populations reach high levels so they do not move into the main crop. Trap cropping requires a great deal of knowledge about the insect’s feeding and egg-laying habits, ability to move, the optimal layout of the trap crop (around the field vs. within the field), and other concerns.

Microbial pesticides: The most commonly used microbial pesticide is the bacterium Bt (Bacillus thuringiensis), which affects the lining of a pest’s stomach. Bt is very selective, affecting only the pests that ingest it while not affecting most beneficial insects. It is also considered safe for humans. There is some controversy over crops that have been genetically engineered to contain Bt. Farmers who use it sparingly contend that its constant presence in a plant will speed the process of insect resistance, making it ineffective and taking away a valuable pest control tool from organic farmers.

Sustainable weed management strategies

The sustainable management of weeds means taking a proactive stance by designing and planning to prevent weeds, instead of addressing weed problems with herbicides and tillage. The following are some strategies used in weed prevention and management:

Intercropping (growing two or more crops together) is one weed-reducing tactic. When different types of plants are grown more closely together, the crops can more easily compete with weeds, as there is less space for weeds to establish. Soybeans interplanted with green wheat benefit from wheat's ability to outcompete weeds for space. Intercropping of corn, beans, and squash is commonly used in Central America, and was used by Native Americans as well. The corn stalks provide a trellis for the beans, beans fix nitrogen in the soil, and the low-growing squash shades out weeds.

Mulch: Mulches, such as straw, can be applied to around crop plants to prevent sun from reaching the soil - greatly reducing the ability of weeds to grow.

Smother crops: Short term plantings of certain crops (including buckwheat) can be used to out-compete and smother weeds.

Allelopathic crops: Allelopathic plants produce chemicals that inhibit the growth of plants around them. Allelopathic cover crops such as rye can be cut and left on the field to prevent the growth of small-seeded weeds. Certain food crops withstand the effects of allelopathy better than others.

Crop rotation: Rotating the field in which a crop is grown from year to year can go a long way towards reducing weed levels. A change in growing conditions (time of cultivation, etc) leaves many weeds unable to adapt and thrive. The same weeds that could do well in a field of annual vegetables may not succeed in rows of grain crops grown close together. Crop rotation also discourages insect pests and disease because pest growth cycles are often linked to a particular crop, so when the crop is moved to a location without the pest it takes a while for the pest to get re-established. In addition, moving the location of crops can inhibit the spread of diseases.

 

Sustainable Livestock and Poultry Production

Most of our meat, poultry, and eggs come from large industrial facilities called CAFOs (Confined Animal Feeding Operations), where many animals are kept close together indoors, unable to engage in their natural behaviors. To prevent disease caused by the poor conditions, animals are given antibiotics, as well as artificial hormones for faster growth or increased milk production. Animal waste is often concentrated in man-made lagoons (resulting in water and air pollution that affects nearby communities and aquatic habitats far away), and workers may be underpaid.

Fortunately, there are still small farms in the US that raise animals in a more humane and sustainable manner. Raising animals outdoors on a pasture where they are free to roam has many benefits for the animals, the environment, and human health. Find pasture-raised meat, eggs, and dairy.

Many farmers use rotational grazing, or management intensive grazing, where pastures are divided into sub-units called paddocks and animals are moved from one paddock to the next in order to give the forage time to recover. This system also prevents undesirable plants from becoming dominant, which often happens as animals in uncontrolled or continuous grazing systems repeatedly eat their preferred forage. Rotational grazing requires an investment in fencing and increased time spent managing the livestock, but pastures can be greatly improved when they are allowed time to recover between grazing.

 

Markets and Profitability

An environmentally sustainable farm is not fully sustainable unless the farmer can make a living. Here are some strategies used by small farms to earn a stable and sufficient income:

Diversification: Growing a diverse array of crops is an insurance against bad weather, pests, and other unpredictable events that can cause a crop to fail. A farmer growing many different crops is less dependent on the success of a single crop and will be less impacted by a single crop failure. Diversification also discourages pest outbreaks, as discussed above.

Direct Marketing: Direct marketing can take many forms, including farmer’s markets, Community Supported Agriculture (CSA) programs, farm stands, pick-your-own, and sales to restaurants. This contrasts with the high integration of production, processing, and distribution in the conventional system, where there are typically a few large farms and processors. Selling directly to consumers gives farms a higher portion of the food dollar and an opportunity to meet face-to-face with consumers to promote their fruit, vegetables, meat, and dairy.

Value-Added Products: For extra income, many farmers add value to their farm products through further processing. Examples of value-added products include: cheese or yogurt, braided garlic, yarn or other items made from wool, jams and preserves, baked goods, soaps, lip balm and other body care items, and much more.

Organic Certification: Certified organic food commands a price premium over conventional or non-certified food. However, the third-party certification process can be prohibitively expensive for some farms. Many small farms generally follow organic principles but are not certified; ask farmers at your local farmer’s market how they grow their produce or raise their livestock.

Want to read about how individual farms practice sustainable agriculture? The Sustainable Agriculture Research and Education (SARE) program profiles 10 farmers from across the country.

 

 

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References

Adam, Katherine, Radhika Balasubrahmanyam, and Holly Born. “Direct Marketing.” National Sustainable Agriculture Information Service. 1999.

“Alfalfa: The Thirstiest Crop.” Natural Resources Defense Council. 7 June 2001.

“Alternative Marketing and Business Practices.” USDA Alternative Farming Systems Information Center.

Bennett, Chris. “Buffer zones: common sense conservation.” Delta Farm Press. 16 August 2007.

Born, Holly and Janet Bachmann. “Adding Value to Farm Products: An Overview.” National Sustainable Agriculture Information Service. 2006.

Clancy, Kate. "Greener Pastures: how grass-fed beef and milk contribute to healthy eating." Union of Concerned Scientists. March 2006.

“Conservation Tillage.” Sustainable Conservation.

“Conservation tillage: the end of the plough?” Food and Agriculture Organization of the United Nations. 3 May 2000.

Cranshaw, Whitney. “Natural Pesticides.” Brooklyn Botanical Garden.

Dufour, Rex. “Biointensive Integrated Pest Management (IPM).” National Sustainable Agriculture Information Service. 2001.

Earles, Richard. “Sustainable Agriculture: An Introduction.” National Sustainable Agriculture Information Service. 2005.

“Essential Steps to a Sustainable Agriculture.” The Kerr Center for Sustainable Agriculture.

Feenstra, Gail et al. “What Is Sustainable Agriculture?” UC Sustainable Agriculture Research and Education Program. December 1997.

“Pasture-Raised.” Sustainable Table.

Sullivan, Preston. “Principles of Sustainable Weed Management for Croplands.” National Sustainable Agriculture Information Service. 2003.

“Sustainability in Agriculture.” USDA Alternative Farming Systems Information Center. 30 July 2008.

“Sustainable Agriculture: Introduction.” Rainforest Alliance.

“Trap Cropping and Insect Control.” Resource Guide for Organic Insect and Disease Management.

“What Is Sustainable Agriculture?” Sustainable Table. http://www.sustainabletable.org/intro/whatis/

Wisniewski, Suzanne L.W., Mark Ritchie, and Kristen Corselius. “Sustainable Agriculture: Making Money, Making Sense.” The Institute for Agriculture and Trade Policy. 2001.

1. Beetz, Alice E. “Rotational Grazing: Livestock Systems Guide.” National Sustainable Agriculture Information Service. November 2004.

Information compiled by Rose Anderson-Gips, Sustainability Intern, Summer 2008