Effects Of Plant Density On Grain Yield Process Of Different Density Tolerant Maize Varieties

The selection of density-resistant varieties and appropriate density can optimize the distribution of light resources in the canopy space of the population and achieve the purpose of increasing yield.This study was conducted at the corn comprehensive test station of Northwest A&F University in 2018.Two maize cultivars,Shanke 6?density tolerance?and Zhengdan958 22?normal type?were grown under four planting density(45000,60000,75000,and 90000^-2 plants hm^-2).This study investigated the effects of plant density on the morphological features,canopy light distribution,grouting parameters and dry matter accumulation,grain-filling of different density tolerance maize varieties.The physiological basis of the difference of maize varieties'density-tolerance was clarified in order to provide the basis for high-yield cultivation and plant type improvement of summer maize in Shaanxi Provence.The main research results are as follows:1.With the increase of density,the grain yield of varieties with different density tolerance first increased then decreased,and the yield reached the maximum at the density of75,000 plants/hm²,respectively 11126.1kg/hm2 and 9876.7kg/hm².Grain yield of shanke 6is increased by 11.2%than that of Zhengdan958.At high density?90,000 plants/hm²?,the panicle grain number and 1000-grain weight of Shanke 6 were 9.7 grains and 17.8g higher than that of Zhengdan958.2.With the increase of density,LAI and leaf direction value increased,and LAI and leaf orientation value of Shanke 6 were greater than those of Zhengdan958 under the same density.With the increase of density,the upper PAR transmission decreased with the increase of density.With high density?90,000 plants/hm²?,the upper PAR transmission of Shanke 6was higher than that of Zhengdan958.It is beneficial to dry matter accumulation and grain filling.3.With the increase of density,the photosynthetic rate?Pn?and transpiration rate?Tr?of leaves of all varieties showed a decreasing trend.At high density?90,000 plants/hm2?,the photosynthetic rate of shaanke6 leaf was higher than that of zhengdan 958.Photosynthetic potential showed the same pattern.4.With the increase of density,the biological yield per plant of the two varieties decreased with the increase of density,while the dry matter accumulation of the population first increased and then decreased with the increase of density.At high density?90,000 plants/hm²?,dry matter accumulation amount and dry matter accumulation amount at maturity stage and after silking of Shanke 6 were respectively 9.9%and 15.9%higher than that of Zhengdan958.Dry matter accumulation and distribution characteristics of Shanke 6 under high density were stronger than Zhengdan958.5.The seed dry weight of the two varieties showed a"slow-fast-slow"S type change with the growth period.With the increase of planting density,the maximal grouting rate,average grouting rate and grain grouting activity stage of the two varieties all showed a declining trend,and the decline of Zhengdan958 was greater than that of shanke 6.At high density?90,000 plants/hm²?,the average grouting rate(G_ave)and the maximum grouting rate(G_max)of shanke6 were higher than that of Zhengdan958?16.1%and 15.6%,respectively?.The active filling period?P?of shanke6 were 2.2 d longer than that of Zhengdan958.To sum up,compared with Zhengdan958,density-tolerant shanke6 cultivar under close planting regulated the vertical position of the upper leaves of ears,improved the light distribution in the middle and lower part of the canopy,maintained a higher photosynthetic green leaf area,delayed the aging of canopy leaves,guaranteed the post-flowering dry matter transport efficiency and grain filling rate,and obtained a higher grain yield.