Minimum tillage and no-tillage winter wheat–summer fallow for low precipitation regions

Dryland wheat (Triticum aestivum L.) is the principal crop grown on 3.35 million ha (8.28 million ac) of the semiarid Inland Pacific Northwest of the United States. In areas with less than 300 mm (12 in) of annual precipitation, challenges for wheat production are similar to those found in the Mediterranean region and Australia. Successful crop production depends on adequate precipitation capture and storage and weed control, which prove problematic under no-tillage (NT), the most effective soil conservation practice. Sweep-tillage (ST) is proposed as an equally effective conservation system, with local conventional wisdom saying that it produces higher yields than NT systems. A study established in 2006 and concluded in 2018 evaluated the performance of NT and ST winter wheat–summer fallow production systems. The null hypothesis for this research assumed no statistically significant differences in any of the soil and plant characteristics measured between NT and ST treatments. Sixteen 0.04 ha (0.10 ac) plots were established in a randomized complete block design, with two rotation entry points for a total of four treatment plots per year replicated in four blocks. Data were analyzed using a generalized linear mixed model. The NT system produced significantly higher crop yields and higher precipitation use efficiencies than the ST system (NT 3.38 ± 0.33, ST 2.66 ± 0.27 Mg ha–1 [NT 50 ± 5, ST 40 ± 4 bu ac–1]). Infiltration rates were higher and soil temperatures were lower in the NT system. The higher yields and lower soil temperatures in the NT system were unexpected and contrary to previous research conducted in this region.