NITROGEN-UTILIZATION EFFICIENCY IN MAIZE AND GRAIN-SORGHUM

The efficiency of utilization of N by maize and sorghum (defined as gr ain yield per unit N uptake) varies under different climatic, soil and management conditions. To maximize N-use efficiency, the minimum N re quirement for a given yield level must be established. The maximum N-u se efficiency (NUE) of sorghum was smaller than for maize (48 vs. 61 g grain(-1) g(-1) N absorbed), and was associated with a higher grain N concentration in sorghum. Cultivar differences in NLTE in sorghum wer e related to grain N concentration. In both crops, NUE declined when N was supplied at high levels or when growth was Limited by moisture su pply. These conditions result in increased stem and grain N concentrat ion. Crop models can integrate the effects of abiotic factors on grain yield, and allow the development of strategies for improving the util ization of N to maximize grain yield and to minimise N losses from the production system. (C) 1998 Elsevier Science B.V.