| Compared with other planting modes,machine-picked cotton planting mode with equal row spacing of 76 cm has the advantages of better chemical defoliation effect and higher quality,but a series of problems such as unstable yield and lack of supporting cultivation measures due to the decrease of density.Moreover,the natural conditions such as drought and little rain in southern Xinjiang and high pressure of agricultural irrigation are the reasons.Therefore,in order to investigate the effects of density and irrigation quota on the utilization of water and nitrogen of cotton under this cultivation mode,as well as the changes in the migration and distribution of groundwater,nitrogen and salt,etc.A major cotton producing areas in southern xinjiang awat,set up three density of 135,000 plants/hm~2(M1,and low density),and 180,000 plants/hm~2,(M2,medium density),225000 plants/hm~2(M3,higher density)and three irrigation level 3150 m~3/hm~2[W1,severe deficit(50%ET_C)],4050 m~3/hm~2[W2,mild deficit(75%ET_C)],4980 m~3/hm~2[W3,full irrigation(100%ET_C)]of the experimental study on the crack area,mainly density area,irrigation quota to deputy district.The effects of irrigation quota under different densities on water,nitrogen and salt migration and utilization of water and nitrogen in machine-picked cotton field with 76 cm equal row spacing were studied.The research results of this paper will provide a theoretical basis for the cultivation of mechanized cotton with 76 cm row spacing of one film and three rows in southern Xinjiang to establish a reasonable planting density and irrigation quota,and provide a theoretical basis for the combination of cultivation measures and soil environment in cotton field with 76 cm row spacing of one film and three rows.The main research results of this paper are as follows:1.Different planting densities and irrigation quotas have significant effects on soil moisture distribution.The distribution of water in the 0-80 cm soil profile appears to increase with the depth of the soil layer;while the increase in density significantly reduces the soil moisture content in the lower layer.The lower layers of M1,M2,and M3 are respectively 5.27%and 4.60 higher than the corresponding upper soil layers.%And 3.73%;resulting in an increase in the uniformity of water distribution,but there is no significant effect on water consumption and water use efficiency.Compared with severe deficit irrigation,the water consumption of full irrigation increased by 43.93%,and on the basis of the increase in the overall soil moisture content,the lower soil moisture content was significantly increased,resulting in the uniformity of the water distribution first increasing and then decreasing.respectively.In addition,there are significant differences in yield and water use efficiency under different density and irrigation quota treatments.The combination of high density and severe deficit irrigation has the highest water use efficiency,reaching 14.08 kg/hm~2/mm,which exceeds the simulated value by 10.18%;Over-irrigation combinations have the highest yield in cotton fields,but there is no significant difference between high-density and reduced-irrigation combinations.2.Density had a significant effect on the content of Ammonium nitrogen,the uniformity of Nitrate nitrogen distribution and the partial productivity of N.However,it had no significant effect on soil Nitrate nitrogen content and Nitrate nitrogen distribution surface polymerization.In other words,the content of ammonium nitrogen in soil decreased with the increase of soil density,and the content of ammonium nitrogen in M1,M2 and M3 were 30.69,29.83 and 27.58 mg/kg,respectively.The proportion of nitrate nitrogen in the upper soil increased at first and then decreased,and M2 treatment was 3.21%and 3.04%higher than M1 and M3 treatment,respectively.On the contrary,respectively.Irrigation quota had significant effects on soil Nitrate nitrogen content,soil Nitrate nitrogen distribution uniformity and surface polymerization.However,it had no significant effect on the content of ammonium nitrogen in soil.In other words,with the increase of irrigation quota,soil nitrate nitrogen content and the proportion of nitrate nitrogen in the upper soil gradually decreased,respectively,while the surface concentration was completely opposite.In addition,density,irrigation quota and the interaction of the two factors had significant effects on the partial productivity of nitrogen in cotton field.In other words,with the increase of density,the partial productivity of nitrogen decreased gradually,which was 13.10kg/kg under M1 treatment.On the contrary,the value of W3 treatment was 13.08 kg/kg.The nitrogen partial productivity of low-density,medium-density and full irrigation combinations was the highest,but there was no significant difference from that of high-density and severely deficient irrigation combinations,reaching 13.21 kg/kg.3.Density and irrigation quota have a significant impact on soil salinity.As planting density increases,soil salt content and surface aggregation coefficient are significantly reduced,and the uniformity of salt distribution increases;increasing irrigation quota,although it can promote leaching,reduce planting densities,the treated soil has salt content,but it can gradually change the salt distribution from"membrane inner bottom aggregation type"to"membrane inner surface aggregation",and the uniformity of salt distribution is significantly reduced.In addition,the study also found that there are significant differences in the salt change and desalination rate under different treatments.With the increase of planting density,the salt change and desalination rate of the 0-60 cm soil layer gradually decrease;while with the increase of the irrigation quota,the opposite is true;and In the interaction of the two factors,as the density increases,the difference between the irrigation quota treatments is more obvious,with the combination of low density and light deficit irrigation,medium density and full irrigation,and high density and full irrigation combination of salinity change and desalination rate The highest are 0.041 g/kg and 18.2%,0.041g/kg and 25.6%,0.055 g/kg and 30.50%,respectively.Therefore,on the basis of comprehensive consideration of environmental and ecological benefits,according to the cultivation measures of winter and spring flood irrigation in southern Xinjiang,it is concluded that in southern Xinjiang,the combination of 225,000 plants/hm2 and 3150 m3/hm2 irrigation quota It is the most suitable cultivation mode for cotton harvesting with 76 cm equal row spacing. |
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