Cover crop and minimum tillage effects on yield, irrigation water use, and net returns

The addition of cover crops and minimum tillage to current row-crop production practices in the mid-southern United States could holistically improve the sustainability of these farming systems. This relatively short-term study was conducted to determine if the addition of these practices into corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotational systems in the region would decrease irrigation water use while improving yield, irrigation water use efficiency, and net returns above production costs. The effects of cover crops and minimum tillage on these parameters were investigated from 2017 to 2019 on six pairs of production fields in northwest Mississippi. A pair was created by dividing a single field that had been under uniform management into two fields that were land leveled and hydrologically separated with an earthen berm. Control fields were managed according to standard practices within the region, which include winter fallow and multiple tillage passes, whereas treatment fields were managed with winter cover crops and minimum tillage. The addition of cover crops and minimum tillage had no effect on yield (p =.09), irrigation water use efficiency (p =.38), or irrigation water applied (p =.83). The net economic return on average across all site years was a loss of US$233 ha^–1. These results reflect the short study period as changes resulting from these practices often occur on a greater time scale. The value proposition for adoption of a cover crop–minimum tillage system will be challenging in the mid-southern United States if potential benefits are to be expected in the early years of adoption.