Study on effect of different nitrogen levels on spatial distribution of cotton bolls and cotton yield.

【Objective】 This paper intends to make sure the optimal nitrogen usage in our area through the study of the effect of different nitrogen levels on spatial distribution of cotton bolls and yield of cotton.【Method】5 levels Nitrogen application were set up by applying the pure nitrogen factor of randomized block designs,and then field biotope experiment was carried out.【Result】Structure of space distribution for bolls is the most optimal for N3 treatment,meanwhile,boll number of upper branch and weight per doll could be increased by 35.08% and 17.44% respectively compared with N1 treatment without nitrogen application,and by 5.25% and 3.06% respectively compared with N5 with higher nitrogen usage;Moreover,weight per outer bolls can be raised by 3.24% and 3.64% respectively compared with lower and higher nitrogen application.In addition,yield of seed cotton and ginned cotton with fertilizer usage is higher than that without fertilizer.The yield increase is the highest under N3(mediate nitrogen application),reaching up to 13.01%;yield increase of N5(higher nitrogen application),is the lowest,coming only up to 5.86%.【Conclusion】 Mediate fertilizer level can optimize the structure of space distribution for bolls and improve its yield.According to revenue formula established with cotton yield and nitrogen usage amount,the amount for the highest yield(5 210.4 kg/hm2) is 332.4 kg/hm2,and for economical yield(5 200.5 kg/hm2) is 290.1 kg/hm2.