Feasibility of Four-Year Crop Rotations in the Central High Plains
2002
Schlegel, Alan J. | Dumler, Troy J. | Thompson, Curtis R.
In the central Great Plains, there has been an increase in summer crops, such as grain sorghum [Sorghum bicolor (L.) Moench] or corn (Zea mays L.), grown in a wheat (Triticum aestivum L.)–summer crop–fallow rotation. This field study quantified the effects of increasing cropping intensity beyond a 3-yr rotation on soil water dynamics and wheat and grain sorghum production and profitability and determined the grain yields necessary to ensure greater profitability over 3-yr rotations. Cropping systems evaluated were wheat–wheat–sorghum–fallow (WWSF), wheat–sorghum–sorghum–fallow (WSSF), and continuous wheat (WW). Available soil water (ASW) at wheat planting was 82 mm greater following sorghum than following wheat; however, fallow efficiency decreased from 50% following wheat to 20% following sorghum. At sorghum planting, ASW was 22 to 32 mm greater following wheat than sorghum. Before sorghum, soil water accumulation during fallow was much greater following wheat than sorghum (168 vs. 60 mm). Fallow efficiency was also greater (34 vs. 23%). Wheat yields were 43% (1.2 Mg ha⁻¹) greater following sorghum than wheat. Grain sorghum yields were 36% (1.5 Mg ha⁻¹) greater following wheat than sorghum. Production costs were similar for all rotations. The WSSF rotation had the highest net returns, about $95 ha⁻¹ compared with $92 ha⁻¹ for a simulated WSF rotation, $76 ha⁻¹ for WWSF, and $49 ha⁻¹ for WW. In this study, grain yields required to make 4-yr rotations more profitable than a 3-yr WSF rotation were recrop sorghum yields of 3.5 to 4.0 Mg ha⁻¹ and recrop wheat yields of 2.5 to 3.0 Mg ha⁻
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