Soil nitrogen analyses and their relation to nitrogen responses in winter wheat

Analyses for nitrate and ammonium were carried out periodically on surface soil samples, obtained at various times throughout the season, from a large number of nitrogen on winter wheat experimental sites. It was found that soil analyses for nitrate alone or nitrate plus ammonia were of no value for prediction of soil‐nitrogen status and nitrogen‐fertiliser responses in winter wheat. Responses of winter wheat to nitrogen fertiliser on freely drained soils where the nitrate nitrogen content of the soil was 15 ppm or more at sowing time were only reduced by this nitrate left over from the previous season when the November–February inclusive rainfall was less than 9 ins.