Dynamics of soil and plant nitrogen in cultivated and no-till spring wheat systems following old pasture

Abstract

Abstract When old pasture is cultivated, nitrogen (N) may be released in quantities that exceed crop demand. No-till cropping is an option that may be more conservative of N. This report considers uptake and distribution of N by a wheat crop established by full cultivation or no-till methods, out of 12-year-old clover/grass pasture. N uptake was more rapid in cultivated soil and in both systems was essentially complete after 40 days. The no-till treatment did show some further N accumulation later in the season during grain fill. Mineral N values and plant uptake rates indicate that N mineralisation was rapid in both systems but only just adequate in no-till. Sampling the soil to 1.5 m depth in the winter following the crop showed both systems to have similar and substantial (about 160 kg N/ha) quantities of NO3-N moving through the profile.