Effects Of Planting Density On Physiological Characteristics And Grain Yield Of Different Plant Types Of Maize

For this problem which has seriously limited the maize production under irrigation area in northern Shaanxi,such as the coordination of maize hybrids and plant density is inconsistent,we used two maize hybrids Shaandan609?compact?and Shaandan8806?flat?with four planting density treatments(45000,60000,75000 and 90000 plants hm^-2)in 2017 and 2018.We analyzed the effect of planting density on morphological characteristics,canopy light distribution,grain filling parameters,dry matter accumulation,nitrogen uptake and transport,canopy senescence,radiation use efficiency and grain yield of different plant types maize,We investigated how maize plant type regulates the senescence of canopy leaves induced by planting density,and elucidated the physiological mechanism of delaying senescence and gained yield of compact maize under dense planting conditions,so as to promote the breeding of maize varieties selection and provide technical support for cultivation of high yield and high efficiency of spring maize in northern Shaanxi.The main study results were as follows:1. Effects of planting density on grain yield and yield formation characteristics of different plant types of maizeThe response of yield components,harvest index and grain filling parameters on planting density of the two maize varieties existed the relatively large differences.Shaandan 609 and Shaandan 8806 reached the highest grain yield at 90000 plants hm^-2(13824 kg hm^-2)and60000 plants hm^-2(9566 kg hm^-2),respectively.The kernels per ear and 100-kernels weight of shaandan 609?24.3 grains,1.2g?and shaandan8806?37.2 grains,1.4g?decreased for each increase in density of 10000 plants hm^-2,and the average 100-kernels weight,the kernels of ear and harvest index of shaandan 609 were 16.1%,14.3%and 9.1%higher than shaandan8806.Compared with Shaandan 8806,The D_max?days to the maximum grain-filling rate?for Shaandan 609 was earlier 3.2 days,the W_max?kernel weight at the maximum grain filling rate?and P?active filling period?were 1.3 g and 4.8 d higher than Shaandan 8806 under 90000plants hm^-2,respectively.2. Effects of planting density on canopy light interception and dry matter production of different plant types of maizeThe leaf length,leaf width,leaf area and photosynthetically active radiation?PAR?transmission decreased,LOV?leaf orientation value?and LAI?leaf area index?and the dry matter production and transportation after silking increased with the increase of plant density.Compare with Shaandan 8806,The LOV was larger and the leaf was short and small at the upper layer,and the leaf was larger at mid and lower layer of Shaandan609,which improved the light distribution in the canopy and increased the light interception at mid and lower layer.The TADM?transfer amount of dry matter?and CGDMT?contribution to grain of dry matter transportation?were 4064.4 kg hm^-2,35.5%?shaandan609?and 2733.6 kg hm^-2,21.9%?shaandan 8806?at the density corresponding to their high yield,respectively.The light interception at the mid layer was significantly correlated with grain yield?r=0.631,P<0.05?and the dry matter accumulation after silking?r=0.661,P<0.01?.3. Effects of planting density on IPAR?intercepted photosynthetically active radiation?and RUE?radiation use efficiency?of different plant types of maizeDense planting improved the IPAR and RUE of different plant-type maize,The IPAR,RUE and dry matter accumulation during the post silking period,and HI?harvest index?of Shaandan 609 were 10.2%,14.8%,48.5%and 9.1%higher than Shaandan 8806 under high density,respectively.Correlation analysis showed that there were significant linear correlations?P<0.05?between grain yield and total nitrogen content?R²=0.694?,RUE?R²=0.813?,and HI?R²=0.382?.4. Effects of planting density on canopy senescence and nitrogen transport of different plant types of maizeThe RGLA_m?relative green leaf area at maturity?decreased by 36.4%and 63.3%,V_m?Mean rate of decrease in RGLA?increased by 40.2%and 34.6%,and T_s?Date of onset of leaf senescence?was advanced of Shaandan 609 and Shaandan 8806 at 90000 plants hm^-2,respectively.Moreover,the mid and lower canopy layer of Shaandan 609 with a strong stay character than Shaandan 8806 under 90000 plants hm^-2.Nitrogen accumulation in leaf,stem and grain of Shaandan 609 was higher than Shaandan 8806 during the post-silking period,and NRE?nitrogen remobilization efficiency?in leaf and stem of Shaandan 609 was 12.1%lower and 17%higher than Shaandan 8806 under high plant density.In summary,compared with Shaandan8806,the upper leaves were shorter and more vertical of Shaandan609 under 90000 plants hm^-2,which increased the PAR interception at the lower canopy,and the leaves are larger and flat at the mid and lower canopy,its increased the IPAR of dense plant population.And the coordination of efficient uptake and transport of nitrogen could delay the leave senescence at the mid and lower canopy layer,ensured a higher photosynthetic green leaf area,improved the light capture in space and in time at the mid and lower canopy layer,improved the photosynthetic characteristics and dry matter production,optimized grain filling rate,promoted more photosynthate distribute to grain,so obtained a higher kernel number and kernel weight,gained the population yield and radiation use efficiency.Therefore,the better coordination of morphology and physiology keeps a higher radiation use efficiency and population yield formation for the compact type hybrid under higher density condition.Thus,it is one of the important ways of high yield and high efficiency cultivation of spring maize when increased plant density combined with compact dense-tolerant maize under irrigated conditions of North Shaanxi.