Wheat tillage and water quality in the Southern plains

Abstract

This study considers the impact of conventional-till (moldboard plow or sweeps) and no-till wheat ( Triticum aestivum L.) management practices on surface and groundwater quality. Concentrations and amounts of sediment, nitrogen (N), and phosphorus (P) in surface runoff, and associated nutrient levels in ground water were determined for seven dryland watersheds at two locations for periods up to 14 years. In general, annual surface runoff was similar for both tillage practices, ranging from 6 to 15 cm. Compared with conventional till, no-till reduced sediment, N, and P loss an average of 95%, 75%, and 70%, respectively. Concurrently, elevated levels of dissolved P (maximum 3.1 mg l −1) in surface runoff, and nitrate-N in ground water (maximum 26 mg l −1) were observed. About 25% more available soil water was in the no-till soil profiles, but this did not translate into increased grain yield. Instead, no-till grain yields were reduced an average 33% (600 kg ha −1) compared witj conventional till, which is attributed to a lower availability of surface applied fertilizer, and increasing cheat ( Bromus tectorum L.) and associated weed problems. From an overall agronomic and environmental standpoint, our results indicate that the management of no-till systems should include careful fertilizer placement and timing.