Effects Of Irrigation Water Amount And Planting Density On Cotton Growth,Water And Nutrient Use In Southern Xinjiang

The double drought of soil and climate in Xinjiang,and the lack of water resources severely restrict the development of local agriculture.Exploring new water-saving irrigation planting models is of great significance for saving water resources,improving the local soil environment,and increasing cotton production in Xinjiang.This test was conducted from April to September 2018 in 2 test fields of the 31st Regiment?86°56?E,40°53?N?,Korla,Xinjiang.Using cotton"Xinluzhong 66"as the test material.Three irrigation levels?W₁:60%ET_C,W₂:80%ET_C,W₃:100%ET_C?and three planting density levels?D₁:210,000 plants/hm²,D₂:260,000 plants/hm²,D₃:320,000 plants/hm²?.A total of 9treatments were conducted to study the effects of irrigation volume and planting density on cotton growth traits,soil temperature,dry matter quality and yield,water use efficiency,plant nutrient absorption and distribution,and soil nitrate nitrogen residual distribution under cotton drip irrigation under film.The following research results were obtained:?1?Irrigation water amount and planting density had a very significant effect on plant height,stem diameter and leaf area index of cotton.Plant height,stem diameter and leaf area index all increased with the increase of irrigation water,plant height and stem diameter decreased with the increase of planting density,and leaf area index increased with the increase of planting density.The single factor of irrigation water and planting density had no significant effect on the height of the initial node and the number of branches,but the interaction of the two factors had a significant effect on the height of the initial node.The minimum initial node height of W₃D₁ was 11.75cm,which was 22.95%lower than that of W₃D₃.?2?The interaction between irrigation water and planting density had a significant effect on cotton yield.Dry matter accumulation and yield increased with the increase of irrigation water,rose first and then fell with the increase of planting density,water use efficiency decreased with the increase of irrigation water,and increased with the increase of planting density.W₃D₂ treatment resulted in a higher seed cotton yield of 7303.61kg/hm²,an increase of 7.5%compared with W₂D₂ treatment and 19.1%compared with W₁D₂ treatment.The dry matter accumulation at harvest time was 22068.36kg/hm²,and the water use efficiency was 1.40kg/m³,an increase of 12.9%compared with W₃D₁ treatment.?3?The irrigation amount and planting density had a significant effect on the nutrient accumulation of cotton in the growth period.The nutrient accumulation of cotton in each period increased with the increase of irrigation amount and planting density.Nitrogen,phosphorus and potassium were distributed in different organs in different growth stages.N and P were distributed in cotton boll>cotton leaves>stems,and K was distributed in cotton boll>stems,>cotton leaves.?4?During the cotton harvest,the content of nitrate nitrogen residue in soil layer0-40cm was relatively high and concentrated.With the increase of soil depth,the content gradually decreased and the distribution was more uniform.When the planting density was the same,the total soil nitrate nitrogen accumulation was W₁>W₃>W₂,and the soil nitrate nitrogen accumulation was reduced by 48.64%and 31.07%respectively compared with W₁and W₃.With the same irrigation amount,soil nitrate nitrogen accumulation was shown as D₃>D₁>D₂ on the whole,and the cumulative nitrate nitrogen amount treated by D₂ was reduced by 9.14%and 12.99%respectively compared with D₁ and D₃.In consideration of comprehensive output,water saving,and reduction of soil pollution residues,100%ET_Cirrigation and a planting density of 260,000 plants/hm² can be used as the optimal irrigation planting model in the Korla region of Xinjiang.