Yield and Soil Water in Three Dryland Wheat and Grain Sorghum Rotations

Abstract

Core Ideas Grain yield of the second wheat crop was 80% of first wheat crop in WWSF. Grain yield of the second sorghum crop was 63% of first sorghum crop in WSSF. Four‐year rotations were similar in productivity to 3‐yr WSF. Water productivity was greater with 4‐yr rotations than continuous wheat. Continuous no‐till did not increase second year wheat and sorghum yields. Diverse crop rotations sustain crop productivity by increasing crop water productivity and improving soil structure. The objective of this study was to compare two 4‐yr winter wheat (Triticum aestivum L.) and grain sorghum (Sorghum bicolor L.) rotations in terms of grain yield, available soil water, and water productivity along with continuous winter wheat. A field study was conducted from 1996 through 2015 on a deep silt loam soil near Tribune, KS. The study consisted of three crop rotations: continuous annual wheat (WW), wheat–wheat–sorghum–fallow (WWSF), and wheat–sorghum–sorghum–fallow (WSSF). Grain yield, biomass, water productivity, and soil water were all greater for sorghum after wheat compared with sorghum after sorghum. Similarly, grain yield, biomass, water productivity, and soil water were all greater for wheat after fallow compared with wheat after wheat. The yield of the second wheat crop was 80% of the first wheat crop in WWSF, whereas the yield of a second sorghum was only 63% of the first sorghum crop in WSSF. The average crop water productivity (7 kg ha−1 mm−1) of the WSSF rotation was greater than the other rotations. On average, the WSSF system produced 2.05 Mg ha−1 yr−1 wheat equivalent yield (WEY), which was similar to the 1.96 Mg ha−1 yr−1 WEY from the WWSF rotation and greater than WW, which produced 1.53 Mg ha−1 yr−1 of wheat grain. A WSF rotation would have produced 2.0 Mg ha−1 yr−1 WEY, so the 4‐yr rotations were not more productive than a 3‐yr WSF rotation.