Tillage Effects on Soybean Yield, Water Use and Water Use Efficiency on a Sandy Loam Soil Under Irrigated Conditions.

Crop production with no-tillage (NT) has been increasing worldwide for several decades as producers seek to reduce input costs of conventional tillage (CT) practices. Few studies have reported the effects of various tillage practices and crop rotations on soybean water use (WU) and water use efficiency (WUE). We hypothesized that NT has a positive impact on soybean WU and WUE in a 2-yr rotation compared to CT. A field study was conducted to evaluate and compare the effect of NT and CT practices on WU and WUE of soybean in a corn (Zea mays L.)-soybean (Glycine max L.) rotation on a sandy loam soil under overhead sprinkler irrigation system in the northern Great Plains. Tillage treatments were replicated five times in a randomized block design. Seasonal WU and WUE for soybean were determined for the 2014 growing season according to the water balance and WUE equations under NT and CT practices. Results showed that soybean grain yield was significantly lower in NT (2351 kg ha^-1) than in CT (2733 kg ha^-1). Soybean yield differences due to tillage may have been associated with variations in soil water content, soil temperature, and plant population between NT and CT practices.  Results also showed significant differences between NT and CT for both soybean WU (434, 418 mm) and WUE (5.4, 6.5 kg ha^-1 mm^-1), respectively.