Water Use Efficiency and Yield Increament Factor of Hybrid Cotton with Mulched Drip Irrigation

A 3 year field experiment for the effects of interaction of water and nitrogen was conducted in the years 2008,2009 and 2010.The experiment included 9 water treatments(55% FC(55% field capacity of 0-60 cm profile of 5-10 cm beside drip irrigation pipe before every irrigation time,the same as below),65% FC,75% FC,W1(3 d 18 mm,irrigation with 18 mm every 3 days),W2(3 d 30 mm),W3(5 d 18 mm),W4(5 d 30 mm),W5(7 d 42 mm),W6(10 d 60 mm) and 4 nitrogen treatments(N1(fertilizing nitrogen with 0 kg/hm2),N2(150 kg/hm2),N3(300 kg/hm2),N4(450 kg/hm2)).Effects of interaction of water and nitrogen on yield and yield components and irrigation water use efficiency(IWUE),total water use efficiency(TWUE)were studied under the different treatments of nitrogen and water during the cotton growth period from enthesis to ripening with mulched drip irrigation.Results showed that the correlation coefficient between seed cotton yield and boll numbers per plant boll weight and dry matter accumulation,reached to extremely significant level.Dry matter accumulation(DMA)showed an indirect effect on yield through boll numbers per plant.Increase of boll number per DMA was the guarantee of a high yield with a cultivation of high boll weight.Under the condition of sufficient water,increase of nitrogen application could cause the adverse effects of IWUE and TWUE.The change of IWUE was not significant in changing the irrigation interval(when the irrigation was applied to 6 mm/d),the maximum irrigation water used efficiency occurs when irrigation interval was 6.5 d and nitrogen application was 258.4 kg/hm2.