Effects of rates and methods of nitrogen application on grain yields and yield components of spring-sown wheats in South Otago, New Zealand

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Abstract
Results are presented from trials in which 0, 25, 50, or 100 kg N/ha was either broadcast before sowing, drilled with the seed, or topdressed after emergence. The form of N was either calcium ammonium nitrate or ammonium sulphate and urea. Grain yield responses were inversely related to yields without N and were predominantly linear for increasing rates of N. An equation describing these effects is presented. Drilling of urea with the seed at 100 kg N/ha caused severe germination injury. N as nitrolime increased grain yields mainly through increases in ear numbers. Kernel weights were slightly reduced by N and numbers of kernels per ear slightly increased in one year out of two.