a1 Agricultural Research Institute of Northern Ireland, Hillsborough, Co. Down
Three experiments were carried out in which nitrogen was applied to spring barley (cv. Midas) either all in the seed bed or as a divided dressing with 10 or 25 kg/ha in the seed bed and 50 or 60 kg applied at emergence or 10, 20, 30, 40, 50, 60 or 70 days after emergence. Applying part of the nitrogen as a top dressing up to 30 days after emergence and 50 days after emergence had no significant effects on the grain and straw yields respectively, compared with applying all the nitrogen in the seed bed. Grain yields were progressively reduced with top dressings from 40 days after emergence (first node stage) onwards. Applications at 60 or 70 days did not give more grain yield than the no-nitrogen control, but gave straw yields which were intermediate between the no-nitrogen and seed-bed nitrogen treatments. Top dressing at 40 days after emergence stimulated tiller survival but did not improve grain yield because there were fewer grains per ear. Thousand-grain weights were lowest with top dressings at 50 days after emergence and grain nitrogen increased progressively with delay in top dressings from 30 days after emergence onwards.
(Received November 10 1983)
(Revised November 10 1983)