Effects Of Planting Density On Growth,Development And Yield Formation Of Different Maturing Maize Varieties

Increasing planting density is one of the important cultivation measures to increase maize yield.In 2016 to 2017,2 medium maturity hybrids(Shandan 609 and Zhengdan 958)and late maturity maize hybrids(Dongdan 60 and Shandan 8806)were selected as test materials in the Yulin Maize Experiment and Demonstration Station,and 4 planting densities were set up:45000,60000,75000 and 90000 plants/hm~2.The physiological characteristics of yield and yield components,grain filling,dry matter accumulation and transport and leaf area were studied.The findings are as follows:(1)2 Annual output results showed that with the increase of density,the yield of maize hybrids increased first and then decreased,and both medium maturity and late maturity varieties had the highest yield in 75000 plants/hm~2 density,the highest yield of medium maturity varieties is 14484.14kg/hm~2,and the highest yield of late maturity varieties is13599.63kg/hm~2.The yield of medium maturity varieties was 9.2%higher than that of late maturity varieties.With the increase of the density,the number of effective panicle per unit area increased significantly,while that of 100-grain weight and grain number decreased.The number of grains per ear of late maturity varieties was greater than that of medium maturity varieties,while that of medium maturity varieties was greater than that of late maturity varieties.(2)The grain weight showed an"S"curve growth in the whole process of grain formation.With the increase of density,the grain weight decreased,the grain weight of medium maturity varieties was significantly larger than that of late maturity varieties.The grain-filling rate showed a single-peak curve,and the grain-filling rate decreased with increasing density.In early stage and middle stage,the medium maturity varieties were significantly higher than the late maturity varieties.The impact of density on the grain-filling dynamics of medium maturity varieties was mainly in middle stage,while the effects on the late maturity varieties were mainly middle stage and late stage.(3)With the increase of the density,the parameters of grain-filling gradually decreased,and the maximum grain-filling rate and average grain-filling rate of medium maturity varieties were greater than late maturity varieties.Correlation analysis showed that active grain-filling period,average grain-filling rate,effective grain-filling time,grain-filling duration of middle stage,average grain-filling rate of middle stage wear significantly and positively correlated to maize yield.The periods of active grain-filling period,effective grain-filling time,grain-filling duration of middle stage and late stage wear significantly and positively correlated with the effective accumulated temperature of middle stage and the average temperature of early stage.The average grain-filling rate of late stage were significantly positively correlated with the average temperature of late stage.The grain-filling of middle stage is the main period for the difference of grain weight,and the average grain-filling rate of medium maturity varieties during the middle stage is significantly higher than that of late maturity varieties.The average temperature of late stage in the analysis of climatic factors is the key factor affecting the increase of grain weight of late maturity varieties.(4)The dry matter accumulation after anthesis,dry matter content after anthesis and total dry matter weight and dry matter accumulation contribution to the grain reached the maximum under the D3 density.The percentage of dry matter accumulation,after anthesis dry matter weight,and after anthesis dry matter quality of the medium maturity varieties were significantly higher than those of late maturity varieties.The dry matter transport rate,translocation rate and contribution rate of stems and leaves of medium maturity cultivars were significantly greater than that of late maturity varieties,and the parameters in stems were significantly greater than leaves.The high-yield material source of medium maturity varieties D3 density is the accumulation of dry matter after anthesis and the contribution of dry matter accumulation after anthesis to grain yield.(5)With the increase of density,the medium maturity varieties had the highest leaf area index under the density of D3,while the late maturity varieties increased with the increase of the leaf area index under the density of D4.Among different maturity varieties,the leaf area index of late maturity varieties was greater than that of medium maturity varieties.With the increase of planting density,the plant height and ear height increased.In summary,in the Yulin Irrigation Maize District,medium maturity varieties Shandan609 and Zhengdan 958 have good potential for yield increase,and the suitable planting density is between 75,000 and 90,000 plants/hm~2.This is mainly attributed to the increase of the dry matter transport rate after anthesis and the grain-filling rate of middle stage.Prolonging the active period of grain-filling,the effective grain-filling time and the grain-filling duration of middle stage can help to further increase maize yield.