| Abstrakt: |
Field experiments were carried out on six sites in eastern Scotland between 1987 and 1989 to determine the effect of nitrogen on the yield, N uptake and grain N concentration of spring barley grown for malting. The effects of fertilizer applications at rates from 0 to 150 kg N ha-1 and the timing of application were studied, using three fertilizer forms: calcium nitrate, ammonium sulphate and ammonium nitrate. Calcium nitrate applications significantly increased grain N concentrations (P < 0·05), and grain yields (P < 0·01 and 0·05) at two sites, above the values obtained with the other fertilizers, but there was no effect at the other sites. Split applications of calcium nitrate increased yields above those from single applications in some treatments at two sites. At low rates, recovery of 15N-labelled fertilizer was greatest when applied as calcium nitrate. Recovery fell at higher rates in calcium nitrate treatments, but rose in ammonium sulphate treatments. Uptake of fertilizer N, during the period of stem elongation in June, was significantly greater (P < 0·05) in the calcium nitrate and ammonium nitrate treatments. Maximum uptake was usually reached by the time of anthesis. Uptake of soil N was not as great during the early sampling periods, but continued up to harvest in most treatments. There was evidence of losses, between anthesis and harvest, of fertilizer N previously taken up by the crop. The uptake of soil N remained constant over the range of fertilizer treatments except with ammonium sulphate, where there was evidence of increased uptake at higher fertilizer rates, possibly due to ‘pool substitution’ of 15N-labelled fertilizer. The variation in soil N uptake between sites was greater than the variation in fertilizer N uptake caused by different forms of fertilizer and different application times. [ABSTRACT FROM PUBLISHER] |
