Effects Of Organic Acid Addition On Field Phosphorus Status And Yield In Cotton Field With Different Phosphorus Fertilization Rates In Xinjiang

Cotton is an important cash crop in Xinjiang,but the phosphorus（P）fertilization rate is unreasonable in many cotton fields,coupled with serious phosphorus fixation in calcareous soils,resulting in lower phosphorus fertilizer use efficiency.The lower phosphorus fertilizer use efficiency in cotton field do not only result in waste of phosphorus resources,but also increase the environmental risk of phosphorus.In order to reduce the chemical phosphorus fertilization rate and improve phosphorus fertilizer use efficiency in cotton field in Xinjiang,different treatments of phosphorus fertilization rates(0,50,100 and 150 kg P₂O₅hm^-2,MAP0,MAP50,MAP100 and MAP150),with and without organic acid addition(organic acid 45 kg hm^-2,OA and control,CK)were set under the field conditions.The characteristics of soil available phosphorus,plant uptake and distribution and yield were measured,and phosphate fertilizer use efficiency and field phosphorus balance were calculated.The results showed that:（1）under CK treatment,Olsen-P reached the maximum value under MAP100 and MAP50 treatmen in 2019 and 2020,while under OA treatment,Olsen-P reached the maximum value under MAP50 treatment in 2019 and2020,The addition of OA in MAP100 treatment is more conducive to the conversion of Ca₈-P and Al-P to Ca₁₀-P.（2）The plant P uptake showed a trend of first increase and then slightly decrease with the increase of P fertilization rate in 2019 and 2020.In CK treatment,the plant P phosphorus uptake reached the highest level at MAP100 treatment,and reached the highest in MAP50 treatment when organic acids were added.The addition of organic acids also increased the proportion of phosphorus distribution to reproductive organs.（3）Under CK treatment,the yield of seed cotton increased with the increase of P fertilization rate in2019 and 2020,and the highest yield under MAP150 treatment.However,under OA treatment,the yield of seed cotton showed a first increase and then decrease trend with the increase of P fertilization rate,and reached the highest value under MAP100 treatment,ucder OA in MAP100 treatment is more beneficial to the transformation of inorganic phosphorus forms.（4）Under CK treatment,the P fertilizer use efficiency increased first and then decreased with the increase of P fertilization rate in 2019 and 2020,and the P fertilizer use efficiency in MAP100 treatment was the highest;however,under OA treatment,,and the maximum P fertilizer use efficiency in MAP50treatment.In conclusion,organic acid addition could improve soil phosphorus availability(proposed dosage:45kg OA+100 kg P₂O₅hm^-2),plant phosphorus uptake,and distribution of phosphorus to reproductive organs at a lower chemical P fertilizer application rate,thus increasing seed cotton yield and P fertilizer use efficiency in cotton field.The results can provide a scientific method and basis for reduction of chemical P fertilizer application and improvement of sustainable phosphorus management in cotton fields in Xinjiang.