Effect Mechanism Of Combined With Water And Fertilizer On Starch Formation And Yield Of Maize Under Drip Irrigation

In order to explore the mechanism of water and fertilizer synergistic effect on starch formation and yield of maize under drip irrigation under the condition of water and fertilizer integration,’ Dika 517 ’and ’Yinyu 274 ’ were used as experimental materials,irrigation amount,nitrogen,phosphorus and potassium were used as experimental factors,four factors and three levels,and L9(43)orthogonal test design was used.A total of 9 treatments were repeated three times.The effects of different levels of water,nitrogen,phosphorus and potassium on growthing development,physiological and ecological characteristics,dry matter accumulation,N,P and K absorption,water use efficiency,starch formation mechanism and yield of maize with direct grain harvest were studied.The results show that:1.The optimal combination levels of maize growth and development in 2019 and 2020 at different levels of water,nitrogen,phosphorus and potassium were A1B1C2D1 and A2B2C2D3.The optimal combination of maize dry matter accumulation in 2019 and 2020 was A2B1C3D1 and A2B1C3D3,respectively.The total dry matter accumulation was 33370.50 kg/hm2 and 34864.80 kg/hm2,respectively.2.Factors affecting SPAD value,photosynthetic parameters and fluorescence parameters of maize functional leaves in 2019 and 2020 were nitrogen>potassium>water>phosphorus and water>nitrogen>phosphorus>potassium,and the optimal combination levels were A3B1C2D2and A1B3C2D3.The primary and secondary factors affecting the relative conductivity,POD,SOD and proline content of maize functional leaves were water and nitrogen,and the optimal combination levels were A2B1C3D3,A2B1C2D3 and A1B3C3D3.The optimal combination of MDA content and CAT was A2B2C2D3 and A1B1C2D2,respectively.Under the optimal combination,SOD,POD and CAT were 287.21 U/g,236.91 U.g-1 FW.s-1 and 61.87 U.g-1.FW.s-1,respectively.It indicated that under each optimal combination,the damage to maize caused by aging and drought stress could be delayed,which was conducive to extending the functional period of maize leaves.3.At the irrigation amount 3 level,N accumulation was the highest at the level of N,P and K,which accounted for 34.62%,32.83%and 39.51%and 49.73%of total N accumulation,respectively.Under irrigation water amount 2 level,N fertilizer 1 level,P fertilizer 3 level and K fertilizer 1 level,P accumulation was the highest,accounting for 57.66%,59.26%,58.44%and 56.15%of total P accumulation in grains,respectively.Under irrigation water amount 1 level,nitrogen fertilizer 3 level,phosphorus fertilizer 3 level and potassium fertilizer 1 level,the highest K accumulation amount was 65.31%,60.48%,61.33%and 60.02%,respectively.4.Each factor in the whole corn filling process in irrigation level 3,nitrogen fertilizer level 1,phosphorus fertilizer level 3 and potassium fertilizer level 2 to maintain a high filling rate.Logistic equation was used to fit the grain filling process of maize under various factors,and the fitting effect was good.The optimal combination level of starch content in maize kernels was A2B1C2D3,reaching 85.49%.The primary and secondary factors affecting the activities of AGPase and UGPase were water>phosphorus>potassium>nitrogen.The primary and secondary factors affecting the activities of SSS and GBSS were potassium>phosphorus>water>nitrogen.The primary and secondary factors affecting the activity of SBE were potassium>water>nitrogen>phosphorus.5.Through RNA-seq technology,differential genes related to starch metabolism were screened out,and they were involved in biological process(BP),cellular component(CC),and molecular function(MF).The enrichment degree of each differential gene metabolic pathway in starch and sucrose metabolic pathways was the highest.There were 17 pathways involved in pathway analysis.Each pathway regulated the expression of enzyme activity in starch and sucrose metabolic pathways,and affected the formation of starch in maize kernels.6.In 2019 and 2020,the optimal combination is A154B27.8C6.65D3.77 and A154B19.46C6.65D3.77 respectively,that is,under the conditions of this test,In 2019,irrigation amount of 2310m3/hm2,nitrogen fertilizer of 417 kg/hm2,phosphorus fertilizer of 99.75 kg/hm2 and potassium fertilizer of 56.55 kg/hm2 were the best,and the yield reached 21842.85 kg/hm2.In 2020,when the irrigation amount was 2310 m3/hm2,nitrogen fertilizer was 291.9 kg/hm2,phosphorus fertilizer was 99.75 kg/hm2,and potassium fertilizer was 56.55 kg/hm2,the highest yield reached 19892.86 kg/hm2.