Animal manure and green manure (legume-N and hay) gradually replace Chemical-N, with following effects:

• Less denitrification, leaching, and volitilization, and less N-use by weeds -- if program is managed properly (e.g., nutrients applied at proper times, close to crop uptake)
• Mineralization rate (plant availability rate) is slow, matching long-term crop needs
• Build-up of soil organic content, structure, ion exchange capacity, and microbial activity (i.e., the "decay process," which is the production of humus, or the conversion of old plant residue into available nutrients for new plants)

Not every sustainable-agriculture farm requires livestock, but farmers who do raise livestock must match the crop farming system not only to local grain markets but also to the crop needs of livestock.

The P and K transition recommendations are keyed to specific needs of the crops and the nutrient balance in the soil.

• Unlike N, which can be added to crop-soil system via symbiotic fixation, the soil supply of P and K can only be replenished by external sources;
• The supply of P and K may be in surplus from conventional crop farming, and may not need replenishment for several years -- especially if improved soil structure, organic content, and pH levels act to increase the availability of existing supplies of P and K to plants;
• Sources of additional P favored by alternative farmers are rock phosphate as opposed to superphosphates (acid-treated), especially in a rotation scheme with green manures or with composting; animal manure is also an important possible source of phosphorus;
• Sources of K favored by sustainable-agriculture farmers are low analysis rock dust as opposed to KCl; more processed K may be needed during transition to sustainable agriculture.

The weed and insect control methods of alternative-agriculture farmers are intimately related to the crop rotation scheme, the tillage practices, and the population dynamics of pests and their natural enemies.

• Interrupting weed and insect life cycles with rotation scheme;
• Ridge tillage;
• Allelopathy (plant tissue residues emitting natural herbicides);
• Mechanical cultivation;
• Adjusting planting rate, time of planting, row and seed spacings, and altering choice of crop or variety;
• Integrated pest management (IPM), which includes regular scouting and "biocontrol" use of other insects and pathogens to fight pests;
• Use of "biologically based" pesticide formulations;
• Focus on economic threshold of weeds rather than visual threshold.

Sustainable agriculture differs from conventional farming in all four elements of the farming system. -- In other words, the switch to sustainable agriculture is a complete change of farming systems. The main uncertainties of farmers making the transition are shown below.

Elements of           Conventional             Alternative farming
Farming	       		  Farming*

Crop rotation         Corn-corn-corn or        Multiple crops, emphasis on
	                  corn-soybeans-corn       legumes and witner cover

Tillage practices     Minimum-till, no-till    Mechanical cultivation and
	                  or modboard plowing      ridge till whenever possible

Fertility program     Chemical fertilizer      Legumes in rotation,
	                  (NPK)                    greater use of organic N,
	                   	                       less chemical N, P and K;
          	           	                       soil structure regeneration

Pest control method   Routine application of   Low input, biological controls,
                      chemical pesticides      mechanical cultivation, crop
                                               rotation, disease-resistant
                                               cultivars, scouting for pests
                                               and beneficials; applying
                                               chemical pesticides as a
                                               last resort.

*Uncertainties:

What happens to yields with less inputs?

Will more labor and management be required?

What happens to profitability -- and how soon?

No. Alternative (sustainable) agriculture depends on far too many variables to be easily simplified into a single, nationwide approach. At least during its current formative stages, alternative agricultureal technology often must be highly "site specific" for most crops and geographic locations.

• Agronomic principles cannot be separated from the economic and philosophical goals of the individual farmer and the individual farm;
• The best results always come from adaptation of techniques to a single farm (in terms of soil, climate, labor, equipment, facilities, livestock needs, markets, and the farmer's skill and knowledge);
• Conversion to sustainable agriculture can be a long-term project -- a matter of several years rather than several months -- and not enough conversions are far enough along to provide answers for each and every new problem confronted by those just beginning to convert.

According to limited survey data, more farmers report a decrease in yields than an increase, but a large number report no change. Others have increased yields.

Reasons given:

Nutrient deficiency (cited by 48 percent)

Weed problems (72 percent)

Farmers do report better yields with time, in making the switch to sustainable agriculutre. Agronomic research also supports this conclusion. Improved soil tilth and water holding capacity, reduced disease pressure and improved soil nutrition are often contributing factors. As shown below, the soil exhibits increasing availability of legume-N in its second year of legumes. ("legume-N" refers to the nitrogen furnished by legumes such as soybeans, which naturally "fix" atmospheric nitrogen to their roots.

Crop rotation is certainly a central element in any sustainable-agriculture farming system.

Developing a crop rotation that not only improves soil condition and prevents buildup of pests but that also suits the following needs of a specific farm:

Growing appropriate crops for the soil-water-climate resources available;

Having markets for the crops in rotation;

Matching crops with available equipment, labor, storage and processing facilities;

Providing the necessary labor and management for the crops grown;

Integrating the crops with livestock nutritional needs;

Identifying the effects that a new crop mix will have on the farm's seasonal cash flow;

Identifying the effect that a new crop mix will have on the farm's eligibility for USDA price support payments.

How do farmers approach the transition to sustainable agriculture?

Gradual withdrawal of potentially harmful chemical inputs and employement of new strategies over period of year;

Conversion of one field at a time, to gain knowledge and experience. (Some researchers recommend about 10 percent of cropland per year.)

Under the 1985 farm bill, yes. In its 1990 "Alternative Agriculture" report to Congress, the U.S. General Accounting Office concluded that farm program changes must be made "To ensure that farmers have the flexibility to use a variety of management approaches, particularly those that emphasize low-input, sustainable agricultural methods." The 1990 farm bill has responded by adding extensive "flexibility" provisions.

Based on these results of interviewing 74 large-scale farmers in depth:

75 percent would diversify into additional crops if they could maintain their existing program crop acreage base;

most are concerned that adopting alternative agriculture practices would require greater management skills and cause greater weed problems, lower yields, and lower profits;

most believe that growing nitrogen-fixing legumes would be "more costly and time-consuming than using commercial fertilizers;"

most believe that the best way to reduce economic risk is to participate in farm programs rather than switch to more crop diversification...

USDA currently operates a broad array of programs designed to spread the word about sustainable agriculture's benefits. Launched in a small way by the 85 farm bill and significantly strengthened by the 90 bill, USDA's sustainable agriculture efforts now include major Agricultureal Research Service, Cooperative State Research Service and Extension Service programs.

Agronomic techniques and principles, focused on integrating specific crop-practice changes with whole-farm systems approach

Skill and amount of labor needed, not only for production aspects but also for overall management

Risk definition, including:

labor availability vs. timely cultivation (in view of variables such as weather, growth stage, pest populations, etc.),

trade-offs between quick, usually effective weed control with chemicals vs. environmental, weather, cost and health risks

Societal concerns, including:

energy savings (less petrochemicals used in farming),

environmental benefits vs. costs (and who pays?)

how to match sustainable agriculture with existing USDA programs, both in conservation and in price support areas

Under the 1990 farm bill, specific sustanable agriculture research is authorized for $40 million per year. To judge what $40 million may buy, consider what $10 million in USDA money plus $14 million in matching state and private money already has baught in the 100 sustainable agriculture projects involving 1,860 farmers funded since 1988.

SUSTAINABLE AGRICULTURE RESEARCH STUDY RESULTS:

• cover-crop practices cut soil erosion and reduce nutrient losses affecting water quality while providing "free" nutrients for following crop;
• switching to rye or other crops that are toxic to weeds often provides effective weed control;
• lower-chemical-input corn, wheat, soybean, rice and vegetable farms can maintain or increase yields;
• use of legumes and other green manures usually pays multiple benefits;
• ridge tillage eliminates herbicide use on some soil types in Midwest corn production;
• disease-free apples can be grown in the Northeast without fungicides;
• grazing sheep in orchard both controls weed and aids diversification;
• switching to three-year rotation boosts wheat yields sharply by breaking the cycle of disease organisms in the root zone;
• low-tech, low-cost gypsum blocks monitor soil moisture accurately enough to boost productivity while lowering costs and saving scarce water;
• manure management systems reduce environmental problems while boosting profitability;
• intensive rotational grazing cuts herbicide use and operating costs while improving year-round forage management.

For further information on sustainable agriculture, contact your local Extension agen, the Soil Conservation Service, or the National Agricultural Library. For information on submitting research proposals to the LISA program, please contact any of the following:

North Central Region:
University of Nebraska
Lincoln, NE 68583
(402)472-2937

Northeast Region:
University of Vermont
Burlington, VT 05405
(802)656-2630

West Region:
Utah State University
Western SARE
Ag Science Bldg., UMC 4865
Logan, UT 84322-4865
(801)797-2257

Alternative Farming Systems Information Center:
National Agricultural Library,
USDA, Room 111
Beltsville, MD 20705
(301)344-3704