Determination of the nitrogen status of soils in the west midlands

Nitrogen release values were obtained by a modified technique involving incubation of moistened soil samples for one week at 35°. the proportion of nitrate in the nitrogen released from different soils varied greatly. Both air‐drying of soils and air‐dry storage of soil samples before incubation increased the nitrogen released during incubation. Nitrogen release values fluctuated during the season and were maximum in the spring and late autumn. Values, obtained from incubating soils immediately after air‐drying, correlated significantly with crop response to nitrogen fertilization.