Effects of Different Ratios of Base and Topdressing Nitrogen Fertilizer on the Leaf Senescence and Yield of Insect-resistant Hybrid Cotton

Pot experiment using equal amounts of nitrogen in different ratios of base and topdressing nitrogen fertilizer i.e.2∶1,1∶1,1∶2,respectively,was completed to study the effects of nitrogen fertilizer types on leaf senescence and yield of insect-resistant hybrid cotton 'Yuza 35'.The results showed that SOD,POD activities,and the content of chlorophyll,soluble protein were lower,and MDA content was higher in leaves on full budding and flowering stage when the ratios of base and topdressing nitrogen fertilizer was 1∶2 applied.But SOD,POD activities and the content of chlorophyll,soluble protein were the higher,and MDA content was lower in leaves after full bolling stage.3.66% and 7.33% more yield was harvested compared with the ratios of base and topdressing nitrogen fertilizer was 1∶1 and 2∶1,respectively.It was concluded that leaf senescence be postponed when the ratios of base and topdressing nitrogen fertilizer was 1∶2.