Value of a one-time sweep application in managing no-till fallow
Farmers across the intermediate rainfall (12–16 inches of annual precipitation) cropping region of eastern Washington traditionally use a tillage-based summer fallow-winter wheat (Triticum aestivum L.) system in their crop rotation. By adopting conservation tillage, farmers have increased implementation of no-till (i.e., chemical herbicide) summer fallow systems to reduce erosion and increase profitability. However, they have expressed concerns regarding adequate seed zone soil moisture for fall seeding of winter wheat and consistent control of tough weeds during the fallow period. The main objective with this research project was to examine the value of a one-time “sweep” cultivation to improve seed zone moisture and kill weeds that can be troublesome with a cost-effective herbicide application (traditionally multiple glyphosate applications) compared to a true no-till fallow (NTF) system. An on-farm trial (OFT) established over four years examined the impact of a single sweep cultivator operation in fallow on seed zone soil moisture, yield, and grain quality. Weed data were not collected, but visual observations were made. The treatments were NTF and a sweep operation (Sweep) replacing the second of three herbicide applications in the NTF system. The OFT was a randomized complete block design with four replications. The Sweep did not affect seed zone moisture, grain yield, or test weight. Grain protein was less following the sweep application but did not affect the market value of the crop. The sweep, as anticipated, was an adequate weed control operation. In conclusion, the Sweep did not increase seed zone moisture, but was effective in removing weeds that can be difficult to control with glyphosate.