Quantifying Nitrogen Mineralization of Oat on Sandy Soil.

The use of spring-planted green manures on sandy soils provides a nitrogen source for subsequent crop growth. Due to the high porosity of these soils and low organic matter content, plant available nitrogen is largely lost to leaching before it can be taken up by the cash crop. The objectives of this study were to measure spring-planted cover crop growth and N-uptake, and determine the interactive effect of a combined oat cover and N fertilizer on in-situ N-mineralization. This was a two-year study at the Hancock Agricultural Research Station in the Central Sands of Wisconsin. The experimental design was a randomized complete block, split-plot design with two cover crop whole-plot treatments (oat and no cover) and two split–plot N-rate treatments (0 and 168 kg-N ha^-1). Cover crops were planted in the spring, grown for six weeks, and chemically terminated. In-situ PVC columns were inserted and incubated in the 0 and 168 kg-N ha^-1 sub-plot treatments and the oat and no cover whole-plot cover crop treatments. Soil columns contained 30 g of Rexyn^TM 300 (H-OH) Beads and incubated for three 30-day time periods and surrounding column soil samples were collected every ten days. Resins and internal and external soil column samples were analyzed for NO₃ and NH₄. Net mineralization calculations displayed a decrease in mineralization in the oat+fertilizer treatment compared to the no cover + fertilizer treatment. These early findings suggest that oats are rapidly decomposing and immobilizing N, which could mean less nitrate loss early in the growing season and more N supply later in the growing season.