Studies on the method of reducing amount of controlled release nitrogen fertilizer applied to cotton cultivated in the Yellow River bottomland

To investigate the effects of reducing amount of controlled release nitrogen( N) fertilizer on growth and yield of cotton cultivated in Yellow River bottomland,we conducted a field experiment using transgenic Bt Cry1A + CpTI hybrid cotton cultivar,CCRI( China Cotton Research Institute) 75with four N fertilizers treatments,including reducing amount( 180 kg·hm- 2) of controlled release N fertilizer( T1),urea applied as base fertilizer and endoplasm coated urea as topdressing fertilizer in flowering stage( T2),the same amount of urea and endoplasm coated urea mixed as base fertilizer and topdressing fertilizer( T3),traditional amount( 225 kg·hm- 2) of controlled release N fertilizer( T4,CK). The results indicated that N applied as T3 could improve the growth and development of cotton,and increase the LAI,dry matter accumulation of vegetative organs and reproductive organs,the number and weight of boll,and analysis of variance showed and the seed cotton yield and lint yield in-creased by 5. 33% and 4. 33% than CK,respectively. But N applied as T1 could decrease seed cotton yield and lint yield by 7. 34% and 7. 28% than CK,respectively,and analysis of variance showed that the seed cotton yield was significantly different.