| The complete mechanization model of cotton planting and harvesting is an important guarantee for the sustainable development of Xinjiang cotton industry.Therefore,it is urgent to popularize the harvest mode of machine harvested cotton.Field trials of 6 different phosphorus fertilizer sites（0,37.5,75,150,300,and450 kg P2O5/hm2）in Manasi County,a typical planting area of machine harvested cotton in Xinjiang.To study the available phosphorus content,cotton plant dry matter accumulation,nutrient uptake characteristics,and root morphological characteristics at different growth stages in machine harvesting cotton.The absorption rules of nutrient absorption and phosphorus utilization efficiency of machine harvested cotton under different phosphorus application conditions were discussed,which provided a theoretical basis for the scientific application of phosphate fertilizer and the promotion of the sustainable development of cotton industry in Xinjiang.The main results are as follows:（1）Phosphorus application can improve the content of available phosphorus and Ca Cl2-P in cotton field soil.In the seedling,bud and flowering periods.The content of available phosphorus in the cotton field under low phosphorus treatment（75 kg/hm2）increased by 23.31%,5.73%and 5.56%respectively.The available phosphorus content（75 kg/hm2,150 kg/hm2）increased by 125.15%,42.16%,47.14%,214.64%,105.57%and 184.07%on average compared with the control.The available phosphorus content of high-phosphorus treatment（300 kg/hm2,450 kg/hm2）was increased by 308.61%,190.91%,169.94%and 373.67%,196.14%and 269.5%on average.The content of Ca Cl2-P in low phosphorus treatment increased by 100.79%,32.22%and 72.23%respectively.The Ca Cl2-P content of phosphorus treatment increased by 70.98%,48.41%,173.46%and 117.99%,132.28%and 115.77%respectively.The content of Ca Cl2-P in high phosphorus treatment increased by 127.70%,117.17%,292.01%and 135.71%,130.3%,and 202.45%on average respectively.It is shown that under the high phosphorus treatment conditions,the content of available phosphorus in cotton soil is significantly increased,and the risk of soil phosphorus leaching is also increased.Phosphorus application can increase the total salt content in the cotton field,especially in the soil surface（0-5 cm）and（5-10 cm）salt content,but it has no obvious effect on the deep（20-40cm）salt content.The effects of different P fertilizer dosages on soil p H were also different.In each growth period,high phosphorus fertilizer application could reduce soil p H.（2）The dynamics of dry matter accumulation in machine-harvested cotton showed an“S”pattern of growth under different phosphorus application conditions.The effect of phosphorus application on the dry matter accumulation of machine harvested cotton was significantly different.The accumulation of dry matter in organs during the early growth period was concentrated in the vegetative organs（stems,leaves）.The Logistic growth simulation equation was used to get the dynamic accumulation of dry matter in different organs of cotton harvested from different phosphorus treatments.The maximum accumulation rate of t0 was about 82 d to 94 d after sowing,that is,on July 12 to July 24.and the appropriate amount of phosphorus can increase the accumulation of total dry matter in the early growth period of cotton plants,so that the accumulation time of dry matter is appropriately extended,which is conducive to the formation of harvested cotton production.Appropriate application of phosphate fertilizer increased the accumulation of nitrogen,phosphorus and potassium in the growth stages of machine harvesting cotton,but excessive application of phosphate fertilizer had no significant effect on nutrient accumulation.The accumulation of N in each organ was as follows:cottonseed>leaf>stem>shell>cottonwool>root.P2O5 accumulated as:leaf>cottonseed>stem>shell>root>cottonwool.The accumulation of K2O was as follows:stem>shell>leaf>cottonseed>root>cottonwool.The accumulation dynamics of N,P and K nutrients in all treatments were consistent with the dynamics of dry matter accumulation.The dynamics of nitrogen,phosphorus and potassium nutrient accumulation is consistent with dry matter accumulation.Phosphorus and potassium showed a slow period in the early growth stages,a gradual acceleration in the middle period,and a slower growth in the later period,which conformed to the“S”curve of plant growth.Nitrogen shows slow accumulation in the early stage,acceleration in the middle stage,and continuous accumulation in the later stage.The Logistic equation was used to simulate the uptake and accumulation of nitrogen,phosphorus and potassium in cotton.The maximum rates of nitrogen,phosphorus,and potassium nutrient uptake by different phosphorus treatments occur from flowering to full bloom.Sufficient supply should pay attention to the application of phosphate fertilizer.Phosphorus can increase the absorption rate of nitrogen,phosphorus,and potassium in machine harvested cotton,and can absorb nitrogen and potassium.Adequate supply of phosphorus must be ensured,and the application of phosphate fertilizer should be emphasized.The nutrient absorption rate shows an overall“S”curve.The influence of different phosphorus application rates on the root morphology of machine harvested cotton indicated that the length of the root length and the length of fine roots all increased with the increase of the amount of phosphorus applied,and phosphorus was applied under the condition of P2（75 kg/hm2）.Compared with the three indicators of no phosphorus,they increased by 83.30%,22.94%and 15.45%respectively.Low phosphorus and high phosphorus treatments all inhibit the root morphology.（3）Appropriate application of P fertilizer is beneficial to increase the output of machine harvested cotton.With the increase of P application amount,P2（75 kg/hm2）and P3（150 kg/hm2）showed the best seed cotton yield,which increased by 7.46%and 10.33%respectively compared with P0 treatment.A reasonable amount of P（75～150 kg/hm2）is beneficial to the absorption of phosphorus in machine-harvested cotton and the improvement of the utilization rate of P fertilizer.The increase of P2O5nutrient uptake with increasing P application rate in cotton plants shows a rising trend.P2（75 kg/hm2）phosphate utilization rate is up to 25.9%. |
