Growing High Yielding Organic Soybeans

In a recent article in the OMAFRA CropTalk newsletter Horst Bohner, OMAFRA Soybean Specialist listed ten ideas to increase soybean yields. I want to include them here with some comments (in brackets) to adapt them for organic crops.

Good Rotation - For a 100% yield potential, soybeans should only be grown 1 out of 4 years. A corn/soy/wheat rotation is also excellent and provides a 98% potential. Ontario research has shown rotation can increase yields 4.2 bu/ac. (A good crop rotation is a basic foundation of any crop program.)

High Yielding Full Season Varieties - Check the soybean variety trial brochure (www.gosoy.ca) before picking a variety. For example, OAC Wallace yields 8 bu/ac more than OAC Bayfield. (Some growers will use a shorter season variety to allow fall wheat or spelt planting).

Early Planting - An early-May planting date compared to late-May will provide about 3.8 bu/ac extra yield. (Organic soybean growers typically need to plant late May as part of their weed control program, a necessary trade-off).

Narrow Rows at the Right Seeding Rate

194,000 seeds/acre in 7.5" rows, 177,000 seeds/acre in 15" rows. Narrow rows can increase yields 3.5 bu per acre. (Most organic soybean growers plant wider rows as part of their weed control program to allow row cultivation. 20" rows would likely be ideal but many have equipment that is better suited for 30" rows. I would recommend 160,000 seeds/acre, which is higher than many 30" recommendations and allows for plant losses due to emergence problems and mechanical injury from weeding equipment. This should give a final plant population of approximately 120,000 plants per acre)

Inoculants - Response (perhaps 1 bu/ac) is likely to be higher if soils are sandy, pH is low, or the field has not been in soybeans for at least 5 years. (Make sure the inoculant product is permitted by your CB).

Timely Weed Control - This is especially important in organic. Plan a multi-technique approach (good management last year, early tillage this spring, harrowing/rotary hoe before and after planting, row-cultivation and a walk through the fields to get critical weeds. In my experience the difference between good weed control and poor in organic soybeans can be 10 bu/ac.)

Fertilizer and Manure - Phosphorous (P) and potassium (K) should be applied according to a soil test. However, manure can provide yield gains even if soil test levels are adequate. Research indicates that fertility can affect yield by up to 6 bu/ac. (Organic farmers more typically use manure or compost instead of purchased fertilizers but it is important not let P and K levels get too low. Manure applications should be managed for the whole crop rotation and it may be more appropriate to apply it before corn or fall cereal crops. Some evidence now indicates there are more soybean aphid problems in soils with low soil potassium levels.)

Appropriate Tillage - When compaction is a problem, tillage is necessary for good yields. If the soil is in good shape, tillage will provide little yield response. (In organic soybeans, tillage is generally needed to manage weeds. Several passes of spring tillage 1-2 weeks apart can help to reduce early weed flushes of annual weeds before planting.)

Horst's tips on insect and disease management and seed treatments are less critical for organic since we do have choices for products to use. In many cases a good rotation, resistant variety, good seed quality, and overall good crop management can help to reduce the need for these pesticide products.

To see the original article on non-organic soybeans go to http://www.omafra.gov.on.ca/english/crops/field/news/croptalk/2009/ct-0309a2.htm