Effects Of Straw Deep Plowing And Phosphorus Application Level On Phosphorus Absorption And Utilization Efficiency Of Maize

In order to explore the effects of straw deep ploughing and phosphorus application level on phosphorus absorption and utilization efficiency of spring maize,Xianyu 335（XY335）and Zhengdan 958（ZD958）were used as test materials in this study,and the three-factor split-plot design was used.In two years of straw returning（1 year of total straw deep plowing:1a;continuous 5 years of straw deep plowing:5a;the depth of straw deep plowing is 35 cm）under the condition of 5 phosphorus levels:P₂O₅ 0 kg/hm²（P0）,P₂O₅ 45 kg/hm²（P45）,P₂O₅ 90 kg/hm²（P90）,P₂O₅ 135 kg/hm²（P135）and P₂O₅ 180 kg/hm²（P180）;based on the analysis of soil physical and chemical properties,agronomic traits and physiological changes of maize roots and shoots,phosphorus absorption and utilization efficiency,the effects of straw deep tillage and phosphorus application level on phosphorus absorption and utilization efficiency of spring maize were clarified.The results are as follows:（1）With the increase of straw returning years,the activity of acid phosphatase in maize roots increased by 20.00%on average,which promoted the synthesis and efflux of organic acids and reduced soil p H.At the same time,a large number of straw rots released nutrients and increased soil acid phosphatase activity by 21.90%,soil alkaline phosphatase activity by 14.13%and soil phytase activity by 61.11%,respectively,which improved the ability to activate insoluble phosphorus and increased the content of available phosphorus in 0～40cm soil layer.The increase of nutrient content not only significantly optimized the root morphology of maize,but also increased the root activity and acid phosphatase activity by an average of 10.08%and 16.67%,respectively.It was also easier to be infected by AM fungi,thus improving the absorption capacity of soil phosphorus.In addition,the root metabolites L-Aspartic acid and 3-Hydroxy-3-Methyl-2-Oxopentanoic Acid were highly expressed,which could increase the absorption efficiency of phosphate fertilizer by 15.29%on average under the indirect effect of acid phosphatase,thereby increasing the plant height,leaf area index and SPAD value of corn at different growth stages.The slow senescence of leaves,the increase of leaf area and the increase of light-harvesting pigments enhanced photosynthesis and increased the synthesis of organic matter.It promoted plant dry matter production and phosphorus accumulation,and finally increased the average yield by 3.84%.（2）With the continuous increase of phosphorus application level,the soil available phosphorus content in 0～40cm soil layer increased continuously,while the soil acid phosphatase,alkaline phosphatase,phytase activity,acid phosphatase activity of maize root and phosphorus uptake efficiency（PUPE）decreased continuously.When the phosphorus application rate was 90 or 135 kg/hm²,the root morphology of maize reached the best growth state in the early growth stage,and showed excellent root activity and mycorrhizal infection status,laying a foundation for the growth of maize.When the phosphorus application rate was 135kg/hm² in the late growth stage,the maize varieties with different phosphorus efficiency showed growth advantages,and their plant height,leaf area index and relative chlorophyll content reached the peak,which made the plants thrive.The accumulation of dry matter and phosphorus in the aboveground part was the most,with an average of 33985.52kg/hm² and 87.71kg/hm²,respectively,so that higher yield could be obtained,with an average of 15.63t/hm².However,phosphorus use efficiency（PUE）was the lowest.（3）Under the condition of full straw returning to the field for five consecutive years,excessive application of phosphate fertilizer will lead to waste of phosphate fertilizer.It is proved that the comprehensive application of appropriate phosphate fertilizer application and multi-year straw deep tillage technology can effectively improve crop yield and phosphate fertilizer absorption efficiency.