Preplanting and Seed Selection

Organic soybeans were grown on approximately 60,000 acres in Iowa in 1998. Though the market remains strong for organic soybeans, determining your market should occur before any acreage is planned. Buyers will help determine the varieties their organic farmers should grow based on their needs. A list of some of the buyers operating in Iowa is included on page 14. All organic soybean varieties are bred for the food-based tofu or natto market (e.g., specific seed size and protein requirements).

The ideal crop preceding soybeans is winter rye, an allelopathic crop, to help prevent weed establishment. In the spring, rye that is less than 8 inches in height can be killed with a field cultivator. If plants are taller, rye should be mowed or cut with a stalk chopper before cultivating or disking to kill the rye. A second cultivation may be necessary if there are any remaining rye plants.

Fall soil sampling will help determine if soil is adequate for soybean production. Adjustments to a

Organic strawberries are commonly mulched with straw to prevent weeds and disease, aid in moisture retention and keep fruits free of soil particles.

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Many organic farmers plant a cover crop of winter rye on ridges prior to their soybean crop to assist in erosion and weed prevention.

Rotary hoes or harrows are the first tillage operation used on organic farms.

Many organic farmers plant a cover crop of winter rye on ridges prior to their soybean crop to assist in erosion and weed prevention.

Row cultivators are used two to three times to control weeds between rows.

proper soil pH of 6.5 to 7.0 can be made through applications of lime in the fall or spring (usually Iowa soils do not require dolomitic lime). Phosphorus may also be required and can be supplied through composted manure or rock powders. Seeds are planted when the soil is adequately warmed for this tropical crop (usually around May 15), 1 inch deep, in a planting population ranging from 175,000 to 225,000 seeds/acre (depending on the variety). Seeds normally are planted in 30 or 36 inch rows, depending on planting/cultivating equipment specifications. Seeds planted in narrower rows have been attempted, but currently, the most economical method of weed management requires cultivators, which usually cannot fit narrow rows.

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