Effect Of Phosphorus Application Level On Soil Phosphorus Component And Photosynthetic Characteristics And Yield

Soybean is an important source of edible protein and oil,and phosphorus is an important element in regulating their growth and development.Soil phosphorus fractions are closely related to crop uptake and accumulation of phosphorus nutrients and can be divided into three categories:labile phosphorus,moderate labile phosphorus and non-labile phosphorus.The application of phosphorus fertiliser changes the content of the soil phosphorus fraction and affects the effectiveness of soil phosphorus.Soybean growth and development cannot be metabolized without light energy,and improving light energy utilization in soybean populations is the key to increasing soybean yields.Scientific and rational application of phosphorus fertilizer is an important tool to improve soybean yields and provide a theoretical reference for the sustainable development of the soybean industry.The experimental site is located in Xiangyang Township,Xiangfang District,Harbin City,Heilongjiang Province,adopting a positioning approach,six conse cutive years of maize cultivation from 2016-2021.This trial continues with soybean planting in 2022.Phosphate fertiliser using heavy calcium superphosphate（P₂O₅:44%）.The three levels of high,medium and no phosphorus fertilization.The trial was set up with a total of 13 treatments,respectively:PH（high amount of phosphate fertilizer in 2016-2022）,PH-N（high amount of phosphate fertilizer in 2016,2017,no phosphate fertilizer in 2018-2022）,PH-H-C（high amount of phosphate fertilizer in 2016-2021,medium amount of phosphate fertilizer in 2022）,PH-H-N（high amount of phosphate fertilizer in2016-2021,no phosphate fertilizer in 2022）;PC（medium phosphate fertilizer from 2016-2022）,PC-N（medium phosphate fertilizer in 2016 and 2017,no phosphate fe rtilizer in 2018-2022）,PC-C-H（medium phosphate fertilizer in 2016-2021,high phosphate fertilizer in 2022）,PC-C-N（medium phosphate fertilizer in 2016-2021,no phosphate fertilizer in 2022）;PN（2016-2022 no phosphate fertilizer）,PN-H（no phosphate fertilizer in 2016,2017,high amount of phosphate fertilizer in 2018-2022）,PN-C（no phosphate fertilizer in 2016,2017,medium amount of phosphate fertilizer in 2018-2022）,PN-N-H（no phosphate fertilizer in 2016-2021,high amount of phosphate fertilizer in 2022）,PN-N-C（no phosphate fertilizer 2016-2021,medium amount of phosphate fertilizer 2022）.Study of changes in soil phosphorus content,phosphorus accumulation in soybean plants,photosynthetic characteristics,morphological indicators and yield at d ifferent levels of phosphorus application.The test results show that:（1）Phosphorus application had an effect on soil phosphorus fraction.Soil phosphorus fraction increased with increasing levels of phosphorus application,significant difference between treatments with and without phosphorus.Long-term high phosphorus and short-term medium phosphorus（PH-H-C）,long-term medium phosphorus and short-term high phosphorus（PC-C-H）and short-term no phosphorus and long-term high phosphorus（PN-H）all helped to increase the phosphorus fraction of the soil,soil available phosphorus,labile phosphorus（H₂O-P,Na HCO₃-Pi and Na HCO₃-Po）,moderate labil phosphorus（Na OH-Pi and Na OH-Pi）,non-labile phosphorus（HCl-P,Residual-P）,and soil total phosphorus contents were always at the highest levels under the high phosphorus（PH）treatment,compared with no phosphorus（PN）application by:131.29%,86.13%,42.23%,16.63%,12.72%.Soybean cultivation favoured the accumulation of available phosphorus,labile phosphorus,moderate labile phosphorus,non-labile phosphorus and total phosphorus in the soil over maize cultivation.（2）Phosphorus application had an effect on phosphorus accumulation in soybean plants.Phosphorus application was beneficial for the transfer of phosphorus fro m source organs to sink organs in soybean plants,and there was a significant difference between phosphorus application and no phosphorus application treatments.Phosphorus accumulation in soybean plants was always at the highest level under the medium phosphorus（PC）treatment,with 47.64%higher in stems,52.44%higher in pod skins and 60.94%higher in seeds compared to no phosphorus（PN）.Short-term no phosphorus application and long-term high phosphorus（PN-H）contributed to the accumulation of phosphorus in soybean seeds,while phosphorus accumulation in soybean plants under the no phosphorus（PN）treatment remained at the lowest level.（3）Phosphorus application had an effect on photosynthetic indicators of soybean leaves.Under high phosphorus-variable phosphorus conditions,all high phosphorus（PH）treatments improved the relative chlorophyll content,light energy acquisition efficiency and chlorophyll fluorescence parameters of soybean;under medium phosphorus-variable phosphorus conditions,long-term medium phosphorus and short-term high phosphorus（PC-C-H）improved the relative chlorophyll content,light energy acquisition efficiency and chlorophyll fluorescence parameters;long-term no phosphorus and short-term high phosphorus（PN-N-H）,short-term no phosphorus and long-term high phosphorus（PN）.The photosynthetic characteristics of soybean plants under long-term non-phosphorus and short-term high phosphorus（PN-N-H）,short-term non-phosphorus and long-term high phosphorus（PN-H）treatments were significantly better than those of the non-phosphorus treatment（PN）,and the difference between the phosphorus and non-phosphorus treatments reached a significant level.（4）Phosphorus application had an effect on soybean morphological indicators.During soybean growth and development,plant height grew fastest from V₅ to R₁,and phosphorus application promoted the growth of plant height and stem thickness,achieving a significant level of difference between treatments with and without phosphorus application;the order of stem thickness/plant height among treatments at R₃ was:PH-H-N>PH-H-C>PH-N>PH in the high phosphorus variable phosphorus treatment;PC-C-H>PC-C-N>PC-N>PC in the medium phosphorus variable phosphorus treatment;PN-C>PN-N-H>PN>PN-N-C>PN-H in the no phosphorus variable phosphorus treatment.Soybean stem thickness/plant height was the highest in the long-term high phosphorus and short-term no phosphorus（PH-H-N）treatment,and was the most resistant to overturning.Phosphorus application had an effect on dry matter accumulation and yield of soybean plants.The order of yield among treatments was:PH-H-C>PC>PH>PC-C-H>PN-C>PH-H-N>PN-H>PN-N-C>PN-N-H>PC-C-N>PH-N>PN>PC-N,with long-term high phosphorus short-term medium phosphorus（PH-H-C）,medium phosphorus（PC）,high phosphorus（PH）,long-term medium phosphorus short-term high phosphorus（PC-C-H）and short-term no phosphorus long-term medium phosphorus（PN-C）all reached significant levels of difference compared to the no phosphorus（PN）treatment.24.60%,23.72%,22.47%,21.72%and 21.43%higher respectively compared to no phosphorus（PN）application.