Effect Of Kernel Size And Sowing Depth On Growth And Yield Formation Of Summer Corn In The Middle Of Sichuan Hilly Basin

Maize is one of three largest food crops in the world,recognized as the golden food.As one of the most important maize producing areas in Southwest China,the degree of mechanization is low,and the drought disaster is frequent in summer,which seriously harms the formation of maize yield and restricts the development of maize industry.Studies had shown that kernel size and planting depth were both important factors affecting the quality of sowing,this test in split-plot design,using ZhengHong 505 as test material that is widely used in the local area,3 kinds of kernel size was assigned to the main plot,3 sowing depth(2,6,10 cm)to the subplot,had investigated the emergence characteristics,seedling growth,root distribution,dry matter accumulation,yield and yield components,The main conclusions.were as follows:1.Emergence rate of maize increased with the increase of kernel size in two year' trial,the increases of big and medium seed compare to small seed were 7.0%?11.3%,after then large and medium seed's seedling grew more prosperous,whose root system was more developed,stem was more stout,leaf area was bigger,dry matter accumulation was more,seedling index was higher,and seedling was more haleness,This difference had a tendency to decrease with the growth process;shallow sowing(2 cm)was conducive to the emergence,in which seedling broke ground and emergence earlier,and had a higher emergence rate,and the appropriate deep sowing(6,10 cm)was conducive to the growth of seedlings,in which seedling was more haleness,this difference had a tendency to increase with the growth process,especially under drought conditions.2.The contents of Chl a,Chl b and Chl in the leaves of seedlings increased with the increase of kernel size and the increase of the sowing depth.With the growth of seedlings,the difference among kernel sizes decreased,and the difference among the sowing depths increased.Under the same light intensity,the Pn,Gs and Tr of the larger grain were higher than that of the small grain,and with the increase of the light intensity,the depth of 10 cm deep sowing(large,medium seed)and 6 cm sowing depth(small seed)increased more significantly than that of shallow sowing(2 cm).Light saturation point,light compensation point,apparent quantum efficiency and the maximum net photosynthetic rate were increased with the increase of kernel size and the increase of the sowing depth,and the difference of light saturation point was biggest,the difference of maximum net photosynthetic rate was the biggest among the kernel sizes.3.The activities of POD,SOD and CAT in the leaves of seedlings increased with the increase of kernel size,and decreased with the increase of the sowing depth,and the difference of SOD was the biggest.The content of malondialdehyde(MDA)decreased with the increase of kernel size and the increase of the sowing depth.Seedling drought degree of the deep sowing(6,10 cm)was low,so the antioxidant enzyme activity and MDA content were both lower.4.Under the condition of large seed and deep sowing,the root system was developed,and root length,root surface area and root volume were all bigger.In the early growth period,the root distribution mainly concentrated in the 0-10 cm soil layer,which occupied more than 80%,with the advance of the growth process,the root grew accelerated,and the distribution of the root system increased gradually,and the proportion of root system in the soil below 10 cm increased gradually.Deep seeding was conducive to root growth and distribution,mainly reflected after jointing and in the deep layer,with the increase of sowing depth,root length,root surface area and root volume were all increased,large and medium seeds were more obvious.5.In the late period of maize growth,big and medium seeds and deep sowing(6,10 cm)could also promote the growth of plants,plant height,stem diameter,leaf area and dry weight all increased with the increase of the kernel size and sowing depth.The difference among kernel sizes was larger in 2016,especially in silking stage,and the difference among the sowing depths was larger in the big mouth,then reduced,and the difference in maturity became larger again.6.With the increase of sowing depth and the increase of kernel size,the yield of maize increased in different degrees,and the difference among the sowing depths was larger.Comparison of two years,yield in 2015 was 9%higher,but the difference of yield in 2016 among treatments was larger,especially among the sowing depths,the differences reached extremely significant level(P<0.01),the mainly reason of yield increased was that panicle traits were improved.