Effects Of Increasing Planting Density And Nitrogen On Yield And Physiological Characteristics Of Different Density-tolerance Maize Hybrids

The experiment was conducted in 2014-2015 at the Maize Technological Innovation Center of the north China plain(NCP) and State Key Laboratory of Crop Biology of Shandong Agricultural University. Two summer maize cultivars, density-resistant hybrid(Zhengdan958) and non-density resistant hybrid(Ludan981), were used as experiment materials to study the effects of different planting densities(52 500,82 500 plant·ha-1) and nitrogen rates(0,90,180,270,360 kg·ha-1) on yield and physiological characteristics of different density-tolerance summer maize. The objective is to study the effects of increasing density and nitrogen application rate on grain yield,photosynthetic capacity,senescence characteristics,nitrogen utilization efficiency of the different density-tolerance maize hybrids,then aimed to seek rational density planting and fertilizing methods,and reference for the yield improvement of summer maize, the main results were as follows:1 Effects of increasing planting density and nitrogen on dry matter accumulation and grain yield of summer maizeThe higher density of 82 500 plant·ha-1can significantly improve biomass, grain yield,ear number, barrenness, lodging rate, barren tip length, while dry matter accumulation of per plant decreased significantly. Under this experimental field condition, increasing density and nitrogen application rate can significantly improve the yield of Zhengdan958, while Ludan981 not, which due to the increase of barrenness and lodging rate. In conclusion,Reducing barrenness is the key to obtain high yield, under the high density. The most optimal plant density and nitrogen rate of Zhengdan958 are 82 500 plants·ha-1,270 kg·ha-1, and the most optimal plant density and nitrogen rate of Ludan981 are 52 500 plants·ha-1,180 kg·ha-1.2 Effects of increasing planting density and nitrogen on grain-filling characteristics of summer maizeTmax advanced, P Shortened, Gmax, Wmax, ultimate growth decreased, under the higher density of 82 500 plant·ha-1,and Tmax, P increased, with the increase of nitrogen rate. The Gmax of LD981 is higher than that of ZD958, However, P, Ultimate growth, Wmax are significantly decreased. The 30 d after anthesis, rate of grain filling of LD981 decrease rapidly, which was delayed of ZD958.The higher density is not useful for grain filling, which lead to the weight of kernels decreasing, especially LD981.3 Effects of increasing planting density and nitrogen on photosynthesis and senescence characteristics of summer maizeThe higher density of 82 500 plant·ha-1can significantly improve leaf area index, canopy light interception, photosynthetic area, However, Pn, SPAD, Fv/Fm, ?PSII, anti-oxidant enzyme activity decreased. At the later growth period, which dropt rapidly; Leaf area index, canopy light interception, photosynthetic area, Pn, SPAD, Fv/Fm, ?PSII, anti-oxidant enzyme activity increased with the increase of nitrogen rate and delayed the leaves senescence process. The rate of senescence of LD981 is higher than ZD958.The higher density is not useful for improving higher photosynthetic capability.4 Effects of increasing planting density and nitrogen on nitrogen utilization efficiency of summer maizeThe higher density of 82 500 plant·ha-1can significantly improve total nitrogen accumulation, nitrogen translocation amount,nitrogen utilization efficiency and nitrogen agronomic efficiency. Under the high density of 82 500 plants·ha-1, the increase of nitrogen rate could improve the assimilating amount of nitrogen after anthesis, nitrogen translocation amount, nitrogen contribution proportion, the nitrogen transition rate and nitrogen transition efficiency of maize. While the nitrogen agronomic efficiency, nitrogen utilization efficiency and nitrogen partial factor productivity are decreased.