Effects Of Integrated Agronomic Management Practices On Grain Yield And Nitrogen Efficiency Of Summer Maize

This study was conducted from2009to2012at State Key Laboratory of Crop Science(36°11’N,117°06’E,158m a.s.l.), Shandong Province, China. The summer maize cultivarZhengDan958was used for experimental material, which is planted most popularly in China.Integrated agronomic management experiment (MT) and Nitrogen test (NT) were designed atthe same time to investigate effects of integrated agronomic management practices on grainyield and nitrogen efficiency of summer maize. The main research results are as follows:1. Effects of integrated agronomic management on grain yield and yield formation ofsummer maizeGrain yield did not increase continually because of applying nitrogen (N) fertilizers;kernels weight and ear number decreased due to excessive N fertilizers, resulting to yieldreduction. Relaying sowing date to the middle of June and applying direct seeding method,high yield and high efficiency treatment (Opt-1) obtained more kernel and ear number thanconventional treatment (CK), which was the main reason for its high yield. Opt-1separatedone-off fertilizer application before sowing and at six-leaf stage, being beneficial to N useefficiency and yield formation. High yield treatment (HY) increased plant population densityto87000plant/ha, gaining the maximum grain yield in two years. As a result of abundantfertilizers, N absorption of HY was significantly higher than other three treatments, lead tolower partial factor productivity of applied N (PFPN) and N use efficiency (NUE). Byreducing fertilizer application and density, further high yield and high efficiency (Opt-2)gained lower yield than HY, but the kernel and ear number were significantly high and grainyield of Opt-2was76.7%higher than that of CK.2. Effects of integrated agronomic management on nitrogen efficiency of summer maizeIn this study, grain yield increased significantly as adding N fertilizers below184.5kg/ha; maize yield did not increased when N application surpassed184.5kg/ha and soilnitrate nitrogen increased significantly. Results showed that grain yield of summer maize did not increase unlimitedly due to increasing N fertilizer application. Plant N absorption andNUE increased when applying N form0to184.5kg/ha; plant N absorption did not increaseand NUE reduced when applying N exceeding184.5kg/ha. That showed applying Nexceeded plant N absorption because of excessive N application and the NUE was low. The Nfertilizer application of Opt-2was18.0%higher than that of CK, and the plant N absorptionof Opt-2was7.88%higher than CK. Opt-2increased PFPN, NUE and N harvest index (NHI)and kept the soil nitrate N content at a lower level, increasing N efficiency significantly.3. Effects of integrated agronomic management on nitrogen efficiency of summer maize3.1Dry matter accumulationIn study, individual dry matter accumulation increased significantly and population drymatter accumulation did not increase significantly as applying N fertilizer. In integratedagronomic management experiment (MT), population dry matter accumulation of HY was thehighest, but individual dry matter accumulation of HY was the lowest; compared to CK,Opt-2obtained higher dry matter increased grain yield.3.2photosynthetic characteristicsComprehensive regulation, such as cultivars, tillage method and agronomic practices(density, sowing date, harvest date and scientific management) can achieve high yield andhigh efficiency of summer maize. In this study, applying direct seeding, a density of75000plant/ha, a sowing date of June15th, and a harvest date of October4th, and separated Napplication, Opt-2gain longer high value duration of leaf area index (LAI), higher plantuniformity, light transmittance and net photosynthetic rate, which was the main reason forhigh yield and high efficiency of summer maize.3.3Grain filling characteristicsIn this study, grain yield increased significantly owing to more kernel number and kernelweight when applying N fertilizers; but yield did not increase significantly and even reducedwhen N fertilizer application exceeding184.5kg/ha. The maximum grain filling rate (Gmax)and grain growth when grain filling rate reached maximum (Wmax) increased significantly;both did not increase when N fertilizer application exceeding184.5kg/ha. Compared to CK,applied treatments increased grain filling active period (P). In MT, the Wmax and Gmax ofOpt-2increased significantly, achieving high yield and high efficiency.3.4Leaf senescence characteristicsResults showed that the chlorophyll Chl a, Chl b and Chl (a+b) content increasedbecause of applying N fertilizers, but the carotenoid (Car) content decreased rapidly and SOD,CAT and POD activity did not increase continually, besides that MDA content increased. Though integrated agronomic management, Opt-2obtained higher Chl a, Chl b and Chl (a+b)content, higher SOD, CAT and POD activity, lower MDA content, being benefit for highyield and high efficiency of summer maize.