Soybean production in the midwestern USA: technologies for sustainable and stable yields

摘要

The two-year maize-soybean rotation is the predominant cropping system of the US Corn Belt (the upper Midwest), and there is evidence that soybean yield in this cropping system has not increased over the past decade. Possible reasons for this includechanges in weather patterns, buildup in soybean diseases and insects, and temporarily decreased breeding progress resulting from rapid incorporation of glyphosate tolerance into cultivars. Yields of glyphosate-tolerant cultivars currently equal or exceedthose of "conventional" cultivars, however. Breeding for tolerance to diseases and insects has generally provided only partial tolerance, and pests continue to reduce yields annually. Studies suggest that planting date targets are generally being met inmost cases, and that seeding rates are within optimal ranges in most fields. There has been an increase in soybean produced using reduced or no tillage, in order to decrease both soil loss and production costs. Research has shown that tillage has littleeffect on soybean yield, however. Seed inoculants and different methods of providing plant nutrients have been found to have little effect on yield. Glyphosate is used on some 75 percent of the soybean area, and provides excellent weed control and little crop injury, though glyphosate-tolerant weed biotypes have begun to appear. Reducing the intensity of soybean in the cropping system might increases yields and yield stability, especially in combination with improved IPM practices, and may offer one way to increase yield.