Strip-crop rotations: Yield spatial structure for spatially coincident and temporally subsequent corn and soybean production

Yield maps are probably the most common tool used in precision agriculture. Yield stability, measured by changes in spatial/map characteristics over years, is an area still requiring research. Our objective was to observe, characterize and explain changes in yield map spatial properties for two different crop sequences grown in the same field at the same time (strip-cropping): corn-soybean-corn (CSC) and soybean-corn-corn (SCC). Two fields were planted in alternating strips of corn (Zea mays L.) and soybean (Glycine max L. Merrill) in 2008. Crop-strip positions were switched in 2009 and both fields were planted entirely to corn in 2010. Yield spatial structure for corn and soybean, within the same field and season, were generally similar. Spatial structure differed with seasonal climate. In a dry year, corn and soybean exhibited lower yield, higher coefficients of variation, smaller range, lower nugget to sill ratio and greater spatial structure than in a moist year. Seasonal weather was most important to yield spatial distribution, while crop species and crop sequence were less important - grown within the same field during the same season, and also across the same seasons. Dry seasons, rather than wet seasons, resulted in greater yield spatial structure and caused corn and soybean to exhibit similar relative yield structure. Corn after soybean exhibited greater yield and less yield spatial structure than corn after corn, indicating that rotation mitigated some effects of seasonal dry weather.