Effects of different nitrogen fertilizer levels on dry matter and N accumulationof cotton under jujube and cotton intercropping

Dry matter and N accumulation of cotton cultivar, CCRI49, were studied under the jujube and cotton intercropping system at 4 nitrogen levels, pure N 0 (N0), 207 (N1), 310 (N2) and 414 (N3) kg/ha. The results show that the cotton dry matter weights and nitrogen accumulations in different treatments are in the Logistic equations, and the biomass and N accumulation in the close crown areas of jujube are higher than those in the far crown areas under the N0 and N1 treatments, while they are opposite under the N2 and N3 treatments. The beginning times and maximum accumulated rates of rapid accumulation of dry matter are delayed when excess or insufficient N fertilizers are applied in the close crown areas, and the accumulations of dry matters in reproductive organs are reduced. The decreased values of metabolin caused by the higher N fertilizer are less than those of the low N treatmnet or nonN treatment. It is shown that the optimal nitrogen rate could accelerate the accumulation of biomass and N at the earlt growth stages, improve excellent photosynthate absorption, accumulation rate and earlier present time of maximum N uptake rate, and benefit to the formation of high cotton yield. Excess and deficiency nitrogen applications are disadvantages for establishment of rational colony.