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

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 NO 3 ‐N moving through the profile.