Wheat-soybean Double Cropping Can Utilize Early-maturing Soybean in Mississippi.
Stephen Kyei-Boahen and Lingxiao Zhang. Delta Research & Extension Center, IITA, C/O IIAM-PAN, Nampula, MS, Mozambique
Double-cropping soybean [Glycine max (L.) Merr.] after harvesting wheat (Triticum aestivum L.) is an important production system in the mid-southern USA. A major problem with this system is the low soybean yield due to the delayed planting of late-maturing cultivars. Field studies were conducted at Stoneville, MS (33o26' N lat) to evaluate the seed yield and net returns from early soybean maturity groups grown in a double-crop system under limited irrigation, and compare the results with those from a full-season system. Soybean cultivars from maturity group (MG) III, IV and V were used. Double-cropped soybean yields ranged from 2055-3767 kg ha-1 and were 10-40% lower than their full-season counterparts. For both systems, the average yield and net returns from group IV, in particular the late IV, were among the highest, whereas those from groups III and late V were generally the lowest. The net returns from the full-season soybean averaged $85 to 274 ha-1 higher than those from the double-cropped soybean; however, the net returns from the double-cropped wheat more than compensated for these differences. The 3-yr average wheat yield was 5170 kg ha-1 and accounted for more than 60% of the combined net returns from the double-crop system. These results indicate that yields and net returns from double-cropped MG III or IV soybean could be equal or greater than MG V cultivars, but the late IV provided the highest yield and economic return. The data further indicated that wheat-soybean double-crop system using MG III or IV under limited irrigation was more profitable than the full-season soybean system.