Agronomic and Economic Comparison of Full-Season and Double-Cropped Small Grain and Soybean Systems in the Mid-Atlantic USA
Browning, Phillip W.
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Increased demand for barley has changed the proportion of crops grown in Virginia and the Mid-Atlantic USA. Winter wheat is the predominant small grain crop, but barley can be a direct substitute, although much less of it is grown. Soybean is grown full-season and double-cropped after both small grains. Historically, wheat was the primary small grain in the soybean double-crop rotation because of its greater profitability. The barley-soybean cropping system is not a new concept in the region, but the literature is outdated. New agronomic and economic data that directly compares full-season soybean, barley-soybean, and wheat-soybean systems using modern cultivars and management practices is needed. The objectives of this research were to: i) determine soybean yield and compare cropping system profitability of the three cropping systems; ii) perform a breakeven sensitivity analysis of the three cropping systems; and iii) determine the effect of planting date and previous winter crop on soybean yield and yield components. Soybean grown after barley yielded more than full-season soybean in two of six locations and more than soybean double-cropped after wheat in three of six locations. Net returns for the barley-soybean system were the greatest. These data indicate that soybean double-cropped after barley has the potential to yield equal to or greater than full-season soybean or double-cropped soybean following wheat, but its relative yield is very dependent on growing conditions. The profitability comparison indicated that the barley-soybean cropping system was generally more profitable than the full-season soybean and double-cropped wheat-soybean systems. This conclusion was supported by the breakeven sensitivity analysis, but remains dependent on prices that have been extremely volatile in recent years. In another study, soybean yields declined with planting date at two of four locations in 2009, a year that late-season rainfall enabled later-planted soybean to yield more than expected. In 2010, soybean yield decline was affected by the delay in planting date at both locations. Winter grain did not affect soybean yield in either year. Yield component data reinforced these results and indicated that the lower seed yield in the later planting dates was due primarily to a decrease in the number of pods.
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