EFFECTS OF HUSBANDRY TREATMENTS ON NITROGEN CONCENTRATION OF GRAIN AND RELATED YIELDS IN WINTER-WHEAT EXPERIMENTS MADE IN SOUTHEAST ENGLAND

Experiments by the Rothamsted staff over 20 yr show that N (protein) concentratiom in wheat is influenced considerably by several husbandry treatments other than total fertilizer N. Even small differences can be of practical importance if values lie close to the minimum standard for bread wheat. In 15 experiments which tested timing of fertilizer N, an extra 60 kg ha-1 would have been needed in autumn to increase grain-N concentration by 0.1% on averge, but only 43 kg in early and 30 kg in late spring. The response to autumn N was similar in a ley-arable rotation experiment. Fertilizer N applied to a previous potato crop gave a grain-N% increase equivalent to a quarter of the fresh application on a silty clay loam soil but none on a sandy loam. Cumulative annual dressings of farmyard manure [FYM] benefited grain-N% as did residues from FYM applied to a previous potato crop, which gave increases equivalent to those from 16 kg ha-1 of fresh fertilizer N. In ley-arable rotation experiments, wheat after arable cropping did not reach bread-quality standard with the largest amount of fertilizer N (150 kg ha-1), but after lucerne, N% values exceeded the threshold value of 2.14% N with all rates. Benefits from lucerne and a grass-clover ley were still considerable when wheat was grown as a 2nd test crop after potatoes. Yield responses to these husbandry treatments tended to be small and positive, except that in the presence of larger dosages of fertilizer N farmyard manure sometimes caused a depression.