Field experiments made in 1984 and 1985 compared the effects of ammonium chloride with those of other nitrogen fertilizers applied to winter wheat in spring. The dressing was divided, 40 kg N/ha in March and 160 kg N/ha in April. In both years take-all in July was at levels which usually decrease yield, and take-all ratings were greatest in plots treated with ‘Nitro-Chalk’ (calcium ammonium nitrate) and least in plots treated with ammonium sulphate, but the differences were not statistically significant. Ammonium chloride and the other treatments, urea and ‘Nitro-Chalk’ with potassium chloride, had intermediate effects and the ranking of treatments according to disease was consistent in both years. In 1984 the mean yield was 8·27 t/ha, range 7·92 t/ha (with ammonium chloride) to 859 t/ha (with ‘Nitro-Chalk’) and in 1985, 821 t/ha, range 7·;42 t/ha (with ‘Nitro-Chalk’) to 8·55 t/ha (with ammonium sulphate). In both years treatments had no significant effects on yields and the relationship between yield and disease was obscured in 1985 because of highly correlated disease and block effects.
Whereas applying spring nitrogen all in the ammonium form seemed to decrease take-all slightly, the effects on yields of winter wheat were inconsistent. There is no evidence of extra benefit to be gained from applying the ammonium as ammonium chloride to crops at risk from take-all in this country, but there may be some benefit in applying KCl with ‘Nitro-Chalk’ top-dressings in the spring.