| In this study,the maize variety Zhenghong 505 was used as a material,and a two-factor split zone test design was used.Sowing date was the main area factor,including spring sowing and summer sowing.The planting density was the secondary factor,including B1-45,000 plants hm-2,B2-52,500 plants hm-2,and B3-60,000 plants hm-2,B4-67,500 plants hm-2,B5-7,500 plants hm-2,and B6-82,500 plants hm-2?5treatments in 2015?.This experiment studied the effects of planting density on plant morphology,population structure,dry matter accumulation,morphological characteristics of stems,mechanical characteristics of culms and yield formation in spring and summer sown maize plants,to provide theoretical basis for reasonable and close planting of spring and summer sowing maize in the hilly region of central Sichuan.The main findings are as follows:1.The plant height and stem diameter of spring sown maize were significantly higher than that of summer sowing.The coefficient of ear height and the coefficient of center of gravity were lower than that of summer sowing.With the increase of planting density,the plant height,ear height,and center of gravity height increased first and then decreased,the ear height coefficient and the center of gravity high coefficient increased,and the stem diameter decreased significantly.The stem diameter was linearly negatively correlated with the planting density.For each planting density increased by 10,000 hm-2,the stem diameter of spring sown corn increased by 1.615 mm,and the stem diameter of summer sown corn increased by 1.436 mm?2015?and 1.183 mm?2016?,respectively.2.The leaf area index of spring sowing was significantly lower than that of summer sowing at B1 density,and significantly higher than summer sowing at B2-B6 density.The LAI of maize increased with the increase of planting density,and they showed a negative exponential function.The canopy transmittance of summer sown maize decreased with the increase of planting density.At the silking and filling stages,there was a negative linear correlation between the light transmittance of the bottom layer and the planting density.When the density increased by 10,000 hm-2,the light transmittance of the bottom layer at the silking stage and the middle period of the filling stage decreased by 3.726%and 2.824%,respectively.There was a negative linear correlation between the angle between the stems and leaves of the upper or the lower leaf of a spike of summer sowing maize and the planting density,and there was a positive linear correlation between leaf orientation value and planting density.For every 10,000 hm-2increase in density,the angle between the stems and leaves of the upper leaf of a spike and that of the lower leaf of a spike were reduced by 1.885°and 3.343°,respectively,and the leaf directional values were increased by 1.704 and 2.801,respectively.3.Spring sowing effectively increased dry matter accumulation of single plant and dry matter accumulation before and after silking stage.However,the accumulation rate of dry matter per plant was lower than that of summer sowing before flowering,and higher than summer sowing after flowering.With the increase of planting density,dry matter accumulation per plant,dry matter accumulation and accumulation rate of single plant before and after flowering were significantly reduced.The population dry matter accumulation of both sowing periods increased with the increase of planting density before silking,and increased first and then decreased with the increase of planting density after silking.In the spring sowing,the dry matter accumulation of the B5population was the highest,and that of the B3-B4 was the highest in the summer sowing.4.Internode diameters,internode dry weights,and internode dry weight per stem in the 3rd,5th,and 7th sections of the maize base of the spring sowing period were higher than those of the summer sowing in the silking period,and were lower than those of the summer sowing in the filling period.With the increase of planting density,the length of the internodes increased,and the internode diameter,internode dry weight,and internode dry weight per stem linearly decreased.There was a positive correlation between the length of internodes and the lodging rate.There was a negative correlation between internode diameter,internode dry weight,internode dry weight per stem,and lodging rate.The puncture strength,crush strength and crimp strength of the 3rd,5th and 7th of the lower base during the two sowing periods decreased as the nodes rose,and decreased as the planting density increased.Puncture strength,crush strength,crimp strength and lodging rate were negatively correlated.5.The yield of spring sown maize was significantly higher than that of summer sowing.The yield of the two sowing dates increased first and then decreased with the increase of planting density.In spring sowing,the yield of B5(75,000 plants hm-2)density was the highest;in summer sowing,the yield of B3(60,000 plants hm-2)was the highest.The high-yielding cultivation of spring maize should delay the senescence of the later leaves,increase the dry matter accumulation after silking,and take the big spike as the main goal on the basis of ensuring sufficient panicles.Summer maize should strengthen pre-spike management,increase dry matter accumulation before silking,and promote grain filling and seed setting to increase the grain weight on the basis of attacking large spikes.In summary,the planting density significantly affected the growth,yield formation and lodging resistance of spring and summer sown maize.In the hilly area of central Sichuan,the planting density of spring maize was 75,000 plants hm-2,and the planting density of summer maize is 60,000 plants hm-2. |
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