Double Crop Soybean in the Mid-Atlantic.

Double cropping increases total production of food, feed, fiber, and/or fuel without additional land requirement. When combined with no-till practices, the additional residue and continuous “green” cover increases soil organic matter, reduces soil erosion and runoff, minimizes deep leaching of nutrients, and generally improves physical, chemical, and biological soil functions. Double cropping soybean with small grain is one of the most common cropping systems in the Mid-Atlantic USA, and represented 30 to 60% of those soybean hectares over the last 20 years. Although the double-crop small grain-soybean system has historically been more profitable than single-crop soybean, late planting (June-July versus April-May) results in lower yields because of inadequate leaf area development. To overcome this leaf area deficiency, steps to must be taken to maximize and protect growth. These include, in order of importance: 1) position soybean for a longer season; 2) grow more leaves; and 3) protect valuable leaf area. Practices that position soybean for a longer season include: a) plant an early-maturing small grain cultivar; b) begin small grain harvest when seed moisture approaches 20%; c) use a stripper header to speed up wheat harvest; d) plant soybean immediately after wheat harvest; and e) choose a late-maturing soybean cultivar. Growing more leaves involve: a) meeting early-season nutrient needs; b) irrigating during the vegetative stages if needed and available; and c) insuring maximum leaf area through variety selection, narrow rows, greater seeding rates, and uniform planting. Finally, because leaf area is so valuable, double-crop soybean may require different pest management strategies for weeds, insect pests, disease, and nematodes. Due to the importance of the double-crop small grain-soybean system, five Mid-Atlantic universities initiated new research and extension programs. An overview of research conducted is presented.