Effects Of Nitrogen Rate And Plant Density On Grain Yield And Nitrogen Utilization Efficiency Of High Yield Summer Maize (Zea Mays L.)

The experiment was carried out in Shandong Agricultural University experimentalfarm,ShanDong Deng Hai Seeds CO., LTD.,and the State Key Laboratory of Crop Biologyfrom2009to2011.The analysis included field experiment and Pool planted test.DH661,ZD958and CS11were selected as experiment materials.In2009,the effects of different plantdensity on grain yield and nitrogen utilization efficiency was studied. From2010to2011,DH661and ZD958were selected as experimental materials to study the effects of grainyield and nitrogen utilization efficiency under different nitrogen rate and plant density withincreasing plant density. The main results as follows:1. Effects of nitrogen rate and plant density on grain yield and the characteristics ofdry matter accumulationThe grain yield increased at first, then decreased with the increment of plant density. Atthe plant density120000plant/ha, the grain yield was the highest, being11292kg/ha.Thegrain yield increased by39.2%compared with the tradional plant density of60000plant/hain the Yellow, Huai and Hai River Valleys Region. With the increment of plant density,therow per ear,keneral number per row,ear length,1000-keneral weight,keneral number per eardecresed while bald length and grain yield increased. With the increment of plant density,therow per ear,keneral number per row,ear length,1000-keneral weight,keneral number per eardecresed while bald length and grain yield increased.In high plant density condition, increasing the nitrogen rates can improve grain yield and keneral number per ear. DH661was consistent with ZD958. With the plant density increasing,dry matter accumulation perplant decreased.Under the plant density of90000plant/ha condition, increasing the nitrogenrates can improve dry matter accumulation per plant,dry matter accumulation after anthesis,contribution proportion of the dry matter of groups after anthesis and dry matteraccumulation of the groups.2. Effects of nitrogen rate and plant density on nitrogen utilization efficiency ofsummer maizeIncreasing the plant density could improve grain yield and nitrogen use efficiency.Withthe plant density increasing,the amount of total nitrogen accumulation, nitrogen partialfactor productivity,nitrogen agronomy efficiency,nitrogen recovery efficiency increasedwhile nitrogen harvest index decreased. Nitrogen transition rate increased significantlywhile assimilating amount of nitrogen after anthesis increased not significantly or decreased,transition efficiency and contribution proportion increased slightly. Compared with60000plant/ha,the plant density of75000plant/ha and90000plant/ha can improve nitrogentransition amount between75000plant/ha and90000plant/ha, the difference did not exsit.The plant density and nitrogen rate of nitrogen partial factor productivity, nitrogenagronomy efficiency,nitrogen recovery efficiency reaching highest are90000plant/ha and120kg/ha. In conclusion, under this experiment field conditon, as far as grain yield andnitrogen efficiency were concerned, the appropriate plant density and nitrogen rate are both90000plant/ha and240-360kg/ha.3. Effects of nitrogen rate and plant density on photosynthetic charactersistics ofsummer maizeUnder the density of90000plant/ha，increasing nitrogen rate can improve grain yield,the special area weight of leaf, photosynthetic pigments content,N concentration of leaf,netphotosynthetic rate.Density effect performed significantly in the10days after anthesis.Compared with60000plant/ha, the net photosynthetic rate decreased by19.67%under theplant density of90000plant/ha while the net photosynthetic rate increased by14.13%underthe nitrogen rate of360kg/ha comparing with the nitrogen rate of0kg/ha. Stomatalconductance and transpiration rate were consitent with photosynthetic rate, the performance of intercellular CO₂concentration is not significant.4. Effects of nitrogen rate and plant density on relative enzyme activity of summermaizeIn the big tetrad stage, compared with60000plant/ha, nitrate reducase activitydecreased severely under the plant density of90000plant/ha. With the increment of plantdensity, superoxide dismutase activity, catalase activity, peroxidase activity decreasedsignificantly，and Malondialdehyde content increased.Increasing nitrogen rate can slowattenuation rate in the late stage of the plant.