An attempt to improve the yield and quality of direct-drilled winter wheat grown continuously

Abstract

SUMMARYSix field experiments on the effects of rate and time of application of nitrogen, three variety trials and one trial combining varieties with rates of application of nitrogen, all on winter wheat grown continuously and direct-drilled on a single farm, are described and the results discussed.The experiments showed that worthwhile yield responses could be obtained to very high rates of N application and that percentage protein in the grain increased linearly with amount of N supplied even to the highest rate (350 kg N/ha) applied. The effects of time of application were variable but there was a suggestion that applying the nitrogen in two doses in the spring gave more yield than a single dose, in one experiment. Applying some N in the autumn gave no more yield than applying it all in the spring.The variety trials gave results reasonably consistent with those of the National Institute of Agricultural Botany but the variety x nitrogen trial showed clear differences between varieties in response to nitrogen; the oldest variety, Maris Huntsman, showed a maximum at about 240 kg N/ha whereas none of the new varieties had reached their maximum by 270 kg N/ha.It is argued that field trials devoted to improving crop yields for a particular farm are worthwhile if site x treatment interaction is large and season x treatment interaction is small.