Effects of Conventional versus Minimum Tillage on Groundwater Nitrate at a Manured Grass Field. Quality Assurance Project Plan

摘要

In cooperation with the Washington State University, Whatcom Conservation District, and Washington State Department of Agriculture, the Washington State Department of Ecology (Ecology) conducted a nitrate study on a 22-acre grass field near Lynden, Washington from 2004 to 2008. One of the study findings was that nitrate concentrations in groundwater reached high levels (maximum of 43 mg/L nitrate+nitrite-N) beneath the field following conventional tillage of the field. This Quality Assurance (QA) Project Plan describes a planned 2009-11 study to compare the effects of conventional tillage with the effects of minimum tillage. During conventional tillage, the soil is disturbed 8 times to a depth of 3 feet, while the minimum tillage method only disturbs the top few inches of soil one time. Because the soil is not completely turned over using the minimum tillage method, there is less opportunity for soil organic nitrogen to oxidize and mineralize to nitrate.