EFFECT OF NITROGEN ON THE METABOLIC ENZYME ACTIVITY OF LEAVES, PROTEIN CONTENT AND YIELD OF SORGHUM (SORGHUM BICOLOR [L.] MOENCH) IN NORTHERN CHINA

With the improvement of breeding level and mechanization, sorghum planting has achieved the transformation from high-stalk and rare-planting to dwarf and high-density planting in China, but there are few reports on dwarf sorghum under high-density planting condition. Therefore, the aim of this work was to study the effect of different nitrogen doses (0, 100, 200 and 300 kg of nitrogen ha(-1)) on its metabolic enzyme activity, the leaf area and Chlorophyll, so as to explore changes of yield and protein content of dwarf sorghum under the high-density planting management in northern China. The results of the two-year trials indicated that chlorophyll content, leaf area and the activity of nitrate reductase (NR) and glutamine synthetase (GS) were positively correlated with yield and protein, 200 kg of nitrogen ha(-1) as the best rate, promoted metabolism enzyme activity, raised leaf area and chlorophyll content, and ensured the highest yield and protein content.