Research On Irrigation And Fertilization System And Fertilization Strategy Of Cotton Under Film

In order to find out the optimal application amount of water and nitrogen and the optimal fertilization strategy in the growth period of cotton under mulch drip irrigation in Northern Xinjiang,this paper carried out the following two research contents:(1)in 2018,the experiment of irrigation and fertilization was carried out,and the irrigation amount(W1:5250 m~3/hm~2,W2:4500 m~3/hm~2,W3:3750 m~3/hm~2,W4:3000m~3/hm~2)and nitrogen application amount(N1:300 kg/hm~2,N2:262.5 kg/hm~2,N3:225 kg/hm~2),to study the effect of different water and nitrogen application rates on cotton growth and soil water and nitrogen distribution characteristics;(2)based on the optimal irrigation and nitrogen application rate combination obtained from the irrigation and fertilization test in 2018,the fertilization strategy test will be carried out in 2019,and the fixed fertilization period in the whole growth period(T1:Fertilization after 0.5 h irrigation,T2:Fertilization after 2 h irrigation,T3:Fertilization after 3 h irrigation,T4:Fertilization after4 h irrigation)and changing fertilization period(T5:fertilization after 4 h in bud stage,fertilization after3 h in flowering stage,fertilization after 2 h in boll stage;T6:fertilization after 3 h in bud stage,fertilization after 2 h in flowering stage,fertilization after 0.5 h in boll stage).Two fertilization flow rates(F1:3.8 L/min?F2:6.1 L/min)were set up T5,T6 treatment during the changing fertilization period..The effects of different fertilization strategies on cotton growth and water and nitrogen use efficiency were studied.Through the above two experiments,the optimal irrigation and fertilization system and fertilization strategy for cotton field in Northern Xinjiang were obtained,which provided theoretical basis and technical support for scientific water and nitrogen management of cotton under mulch drip irrigation in Xinjiang.The main research results are as follows:(1)In the experiment of irrigation and fertilization system,the effect of irrigation amount on the growth index of cotton was significant.The plant height,stem diameter,Lai and aboveground dry matter quality of cotton increased with the increase of irrigation amount,and the effect of irrigation amount on Lai,aboveground dry matter quality,cotton quality and plant morphological index of cotton was greater than that of nitrogen application.When the irrigation amount is 3750 m~3/hm~2 and the nitrogen application amount is 262.5 kg/hm~2,the boll number per plant,boll quality and yield of cotton reach the highest,and significantly improve the quality of cotton,and the water use efficiency and irrigation water use efficiency of cotton reach the highest.(2)The surface water content of soil increases with the extension of growth period;the amount of nitrate nitrogen and ammonium nitrogen in 0-20cm soil layer is relatively high.With the increase of irrigation and nitrogen application,the degree of nitrogen leaching to deep soil increases continuously.When the amount of nitrogen application is 262.5 kg/hm~2,the content of nitrate nitrogen in root layer is relatively high.To sum up,the amount of nitrogen application is 262.5 kg/hm~2,and the amount of irrigation is 3750 m~3/hm~2,which can be used as the optimal combination of water and nitrogen application in this area.(3)The changes of fertilization period and flow rate had no significant effect on the growth of leaves,branches and buds.Under the condition of fixed fertilization period,in the seedling stage and bud stage,the later fertilization period is more conducive to the increase of plant height,stem diameter and aboveground dry matter quality;after flowering stage,fertilization after irrigation for 2 hours can promote the growth of plant height,stem diameter,aboveground dry matter quality and boll number of cotton.Under the condition of changing fertilization period,when the fertilization flow rate is 3.8 L/min,it is more conducive to the accumulation of dry matter quality in the shoot.When the fertilization strategy of3 hours irrigation in bud stage,2 hours irrigation in flowering stage,0.5 hours irrigation in boll stage and6.1 L/min fertilization flow rate was adopted,the growth of plant height and stem diameter in each growth stage was promoted,and the yield and boll number per plant were improved.The yield under the condition of changing fertilization period was significantly higher than that under the condition of fixed fertilization period.(4)There was no significant difference in length,uniformity,specific strength and elongation between fixed and changed fertilization periods.The effect of different fertilization rate on cotton quality is less.There was no significant difference in water and nitrogen use efficiency among the treatments at fixed fertilization time.Under the condition of changing fertilization period,Makrolon value is significantly larger.When the fertilization strategy of bud irrigation for 3 hours,flower irrigation for 2hours,boll irrigation for 0.5 hours,and fertilization flow of 6.1 L/min,it can effectively improve water use efficiency,irrigation water use efficiency and nitrogen partial productivity.To sum up,changing fertilization period:fertilization after 3 hours of irrigation in bud stage,2 hours of irrigation in flower stage,and 0.5 hours of irrigation in boll stage;fertilization flow rate is 6.1 L/min,which can be used as the best fertilization strategy in this area.