Water Quality Impacts and Yield Comparisons Between Conventional Tillage and Two Conservation and Tillage Systems Under Furrow Irrigation in the Semi-Arid Western United States.

Conservation tillage is a vital component for preventing soil loss and reducing impacts to water resources from nutrient and sediment runoff. However, a concern for furrow irrigators is the ability to uniformly irrigate with high amounts of residue and achieve profitable yields using conservation tillage. The purpose of this study was to assess yield and water quality differences between three different tillage systems, conventional till (CT), minimum till (MT), and strip till (ST) under furrow irrigated grain corn for two growing seasons. In 2011, this field study began in northeastern Colorado on farm scale plots, with each tillage system replicated twice. Water runoff samples were collected in each plot at the bottom of the field during six irrigation events during the growing season at 0,120, and 240 minutes after initial water runoff. These samples were taken using small weirs installed at the end of the furrows. Furrow flumes were also installed to measure water flow rates and runoff volume to determine sediment and nutrient load. Laboratory analyses of runoff samples were conducted to quantify total phosphorus and nitrogen, total soluble phosphorus, ortho-P, nitrate, and sediment levels. Results from 2011 revealed that ST had the lowest flow rate, the least amount of sediment loss, and thus less total nutrient loss. Additionally, grain corn yield for ST was the highest of the three tillage systems, followed by CT and MT having comparable yields to each other. We attribute the higher yield of the strip tillage system to the data showing lower flow rates and higher infiltration in the ST plots compared to the other tillage systems.