Effects Of Phosphate Fertilizer Types And Drip Irrigation Belt Location On Cotton Root Growth And Phosphate Fertilizer Utilization Efficiency

[Objective] Unreasonable application of phosphorus fertilizer will affect the supply of soil phosphorus nutrients,resulting in reduced crop yields and phosphorus fertilizer utilization,leading to resource waste and increased environmental pollution.In recent years,people have improved cotton yield and phosphorus fertilizer utilization efficiency by changing fertilization methods and drip irrigation phosphorus fertilizer types.This study investigated the movement of available phosphorus content in soil by drip application of different phosphorus fertilizer types through phosphorus fertilizer type experiments,compared the effects of different drip irrigation phosphorus fertilizers on cotton growth and yield,compared the dynamic distribution of available phosphorus content in soil by drip irrigation belt location and phosphorus fertilizer type experiments,and clarified the distribution of available phosphorus content in cotton field soil and cotton root growth and distribution by drip irrigation belt location and phosphorus fertilizer type experiments,Compare the effects of drip irrigation belt location and phosphorus fertilizer type on cotton growth,yield,and phosphorus fertilizer utilization efficiency,to provide theoretical basis for the appropriate phosphorus fertilizer type and drip irrigation belt location in Xinjiang drip irrigation cotton field.[Methods] Field plot experiments were conducted,including a single factor experiment on phosphorus fertilizer types and a two factor experiment on drip irrigation belt location and phosphorus fertilizer types.The phosphorus fertilizer type experiment was conducted in 2020,using three phosphorus fertilizers:monoammonium phosphate(MAP),phosphoric acid(AP),and ammonium polyphosphate(APP),and using no phosphorus fertilizer(P0)treatment as a control.Two factor experiments on drip irrigation belt location and phosphorus fertilizer type were conducted from 2021-2022.Two types of drip irrigation belt position treatment were set up in the experiment:(1)entrainment(drip irrigation belt is laid in the middle of the narrow row of crops;N),and(2)side belt(drip irrigation belt is laid 10 cm between the wide rows of crops,W).Three types of phosphate fertilizers:monoammonium phosphate(MAP),phosphoric acid(AP),and ammonium polyphosphate(APP).[Main results](1)Within a irrigation and fertilization cycle(7 days),after drip application of three phosphorus fertilizers(monoammonium phosphate,phosphoric acid,and ammonium polyphosphate),the available phosphorus in the soil is mainly distributed in the range of 0-5 cm on both sides of the emitter and 0-15 cm in the vertical depth.Phosphoric acid treatment had the highest average content of available phosphorus in soil during 1-3 days;The average content of available phosphorus in soil under ammonium polyphosphate treatment was the highest within 5-7 days.Applying phosphorus fertilizer significantly increased the available phosphorus content of 0-60 cm soil(especially 0-40 cm)in drip irrigated cotton fields.Phosphoric acid treatment can increase the available phosphorus content of 0-40 cm soil in the early stage(bud stage)of cotton.The content of available phosphorus in soil 0-40 cm under ammonium polyphosphate treatment was significantly higher than that under phosphoric acid and monoammonium phosphate treatment during the middle and late stages of cotton growth(flowering stage to boll opening stage).(2)After drip application of three phosphorus fertilizers,ammonium polyphosphate(APP)treatment significantly increased cotton growth and yield,as well as phosphorus utilization efficiency.Compared with monoammonium phosphate(MAP)and phosphoric acid(AP)treatment,total dry matter increased by 7.76 and 7.35 percentage points,total phosphorus absorption increased by 11.25 and 9.57 percentage points,yield increased by 7.7 and 6.0 percentage points,and phosphorus utilization efficiency increased by 43.16 and37.51 percentage points,respectively.(3)Within a irrigation cycle(7 days),the available phosphorus content of the three types of phosphorus fertilizers in the soil is mainly distributed between crop rows under the entrainment,mainly concentrated in the 0-10 cm soil layer;The effective phosphorus content of the soil in the side zone treatment is mainly distributed near the fertilization point.The horizontal mobility of the three types of phosphate fertilizers is APP>AP>MAP,and ammonium polyphosphate treatment can increase the effective phosphorus content in the 0-15 cm soil layer in the lateral zone.During the cotton bud stage,AP treatment can increase the soil available phosphorus content during entrainment,while APP can increase the soil available phosphorus content during both entrainment and lateral entrainment from flowering stage to boll opening stage.Compared with MAP and AP treatments,APP treatment can increase the available phosphorus content of 0-60 cm soil.(4)Under different drip irrigation belt positions,compared with the entrainment treatment,the side belt treatment can significantly increase the root weight,root length,and root volume of cotton.Under the lateral band,compared with AP treatment,APP significantly increased cotton root weight and root volume by 46.25 and 5.22 percentage points,respectively.Lateral bands can promote the distribution of cotton root length density at 20-30 cm of soil and the growth of cotton root weight at 0-10 cm.(5)Compared with MAP and AP treatments,APP treatment significantly improved cotton growth and phosphorus uptake,resulting in an increase of 5.9% and 7.8% in yield and a 32% and 16% increase in phosphorus utilization efficiency,respectively.The side band treatment significantly improved cotton growth and phosphorus absorption compared to the band treatment,resulting in a 6% increase in yield and a 32%increase in phosphorus fertilizer utilization rate compared to the band treatment.[Conclusion] Through two consecutive years of experiments on different drip irrigation belt locations and phosphorus fertilizer types,it was found that ammonium polyphosphate treatment in the side belt can improve the mobility of soil available phosphorus,increase the content of available phosphorus in 0-30 cm soil,promote the growth of cotton roots,and increase the root length density of 20-30 cm and the root weight of0-10 cm cotton.Compared to monoammonium phosphate and phosphoric acid treatments,ammonium polyphosphate treatment increased cotton biomass and phosphorus uptake,thereby improving cotton yield and phosphorus fertilizer utilization.Therefore,the use of side band pipe arrangement in drip irrigation cotton fields in Xinjiang and the selection of ammonium polyphosphate as the main phosphorus fertilizer can effectively improve cotton yield and phosphorus fertilizer utilization.