Results from two experiments with winter wheat, comparing top-dressings of a liquid N-fertilizer either alone or with added herbicide or mildew fungicide or both, and of 'Nitro-Chalk' without or with herbicide or fungicide or both

Experiments with winter wheat in 1972 and 1973 tested all combinations of ‘Nitro-Chalk’ ν. liquid N-fertilizer, 56 ν. 112 kg N/ha, 0 ν 5·6 1/ha of herbicide (2·8 kg acid equivalent/ha) and 0 ν 0·7 1/ha of mildew fungicide, all applied at growth stage 4–5 of the Feekes scale. The liquid fertilizer (26 % N) was a solution of ammonium nitrate and urea, the herbicide was a mixture of dichlorprop and MCPA and the mildew fungicide contained 75 % (w/v) of the active ingredient tridemorph.

The herbicide and mildew fungicide were sprayed either alone or together and neither scorched the wheat leaves. Liquid N-fertilizer by itself slightly scorched the wheat leaves and scorch was increased by adding herbicide to it, but more by adding the fungicide and most by adding both; it was then severe, especially with 112 kg N/ha.

Weed control after adding herbicide to the liquid fertilizer was at least as good as from herbicide sprayed alone.

In July, foliar diseases were much more severe with 112 than with 56 kg N/ha, but effects of the other treatments, including fungicide, on foliar diseases, were then very small.

With 56 kg N/ha, yields were slightly larger with ‘Nitro-Chalk’ alone than with the liquid N-fertilizer alone, but with 112 kg N/ha they were slightly larger with the liquid fertilizer; adding herbicide to the liquid fertilizer did not change these results. With either amount of N, adding mildew fungicide to the liquid fertilizer made it less good than ‘Nitro-Chalk’, presumably because of the damage from leaf scorch; adding both herbicide and fungicide to the liquid fertilizer increased the damage.