The Study On Competition And Control Threshold For Solanum Nigrum L. And Mechanical Harvest Cotton

Solanum nigrum L.is an annual dicotyledonous Solanaceae weed.Its occurrence in Xinjiang cotton fields is increasing year by year.It is the dominant weed in northern Xinjiang cotton fields.Solanum nigrum L.harms cotton and affects its growth and development.In order to clarify the impact of Solanum nigrum L.competition on cotton growth and the economic threshold of Solanaceae in machine-harvested cotton fields,the effects of Solanaceae population density on cotton nutrients,physiology and biochemistry,agronomic and economic characteristics,and the duration of Solanum nigrum L.damage on cotton were studied,The influence of agronomic traits and economic traits.The results of the study are as follows:1.In the cotton seedling stage,the stress of Solanum nigrum L.significantly increased the phosphorus content of cotton leaves.When the density of Solanum nigrum L.was 4plants/m²,the nitrate nitrogen content of cotton leaves increased significantly.In the bud stage of cotton,Solanum nigrum L.stress can increase the nitrate nitrogen content of cotton leaves and reduce the phosphorus and potassium content of cotton leaves.During the flowering and boll stage of cotton,Solanum nigrum L.stress can increase the nitrate nitrogen and phosphorus content of cotton leaves,and significantly reduce the potassium content of cotton leaves.In terms of cotton physiological and biochemical indicators,Solanum nigrum L.stress reduces the soluble protein content of cotton leaves at the seedling stage,and significantly reduces the soluble sugar content in cotton leaves at the seedling stage.The trend of increasing and decreasing,Solanum nigrum L.stress will affect the quality of cotton fresh matter.In the cotton bud and boll stage,when the density of Solanum nigrum L.exceeds 4plants/m²,it will have a significant effect,and the degree of influence will increase with the increase of Solanum nigrum L.density.2.When cotton Solanum nigrum L.competition process,the cotton plant height,stem diameter,stem section increases the number density decreases Solanum nigrum L.,Solanum nigrum L.density of 4 plants/m²,significantly reduced plant height.Solanum nigrum L.has a significant impact on the number of bolls and yield in the middle of cotton.When the density of Solanum nigrum L.reaches 15 plants/m²,the cotton yield loss rate is 100%。The cotton yield loss rate of Shihezi in Xinjiang is in line with the logarithmic function y=12.594ln（x）+58.025.The allowable level of economic harm for artificial control of Solanum nigrum L.is4.98%,and the economic threshold is 0.016 plants/m².3.When Solanum nigrum L.continued to damage cotton,the plant height,stem thickness,and the number of main stem nodes decreased with the increase of the damage time.When the damage continued for 2 weeks,the cotton plant height decreased significantly.When the damage of Solanum nigrum L.lasted for 8 weeks,the number of bolls in the upper and lower parts of the cotton was significantly reduced.When the damage lasted for 6 weeks,the number of bolls in the middle was significantly affected.The power function model y=2.116x^1.380 can better fit the relationship between the cotton yield loss rate of Shihezi,Xinjiang and the duration of damage to the Solanum nigrum L.When the symbiosis period of Solanum nigrum L.and cotton is 6 weeks,the cotton yield loss rate reaches 17.54%,more than 15%.4.Cotton plant height,stem thickness,and number of main stem nodes decrease significantly with the decrease of the space distribution distance between Solanum nigrum L.and cotton.When the distance between Solanum nigrum L.and cotton is 50cm,the height of cotton is significantly reduced.The number of cotton fruit branches,buds and bolls all showed a decreasing trend with the decrease of the distribution distance.In terms of nutrients in cotton leaves,as the distance between Solanum nigrum L.and cotton decreases,the nitrogen and phosphorus content of cotton leaves gradually increase,while the potassium content shows a decreasing trend.In terms of physiological and biochemical indicators of cotton leaves,the content of soluble sugar and soluble protein decreased with the decrease of distance,and the content of malondialdehyde increased with the decrease of distance.After Solanum nigrum L.vulgare harmed cotton,compared with no Solanum nigrum L.vulgaris,the content of available phosphorus in cotton field soil increased.The content of available phosphorus in 0-10cm soil increased significantly,and the content of available nitrogen showed a decreasing trend,and there was no significant difference.In summary,when Solanum nigrum L.competes with cotton,it will compete for the nutrients of cotton,change the physiological and biochemical indicators of cotton,and affect the soil nutrient content of the cotton field.The cotton yield loss rate of Shihezi in Xinjiang and the density of Solanum nigrum L.accord with the logarithmic function y=12.594ln（x）+58.025,the allowable level of economic harm to artificial control of Solanum nigrum L.is4.98%,and the economic threshold is 0.016 plants/m².The relationship between the rate of cotton yield loss and the duration of damage by Solanum nigrum L.accorded with the power function model y=2.116x^1.380.In agricultural production,the population density of Solanum nigrum L.in the machine-harvested cotton field should be controlled below 160 plants/hm².When the density of Solanum nigrum L.is greater than 4 plants/m²,the time of prevention and control of Solanum nigrum L.in cotton should be no later than 20 days before cotton topping.