| In this study,the maize variety Zhenghong No.6 was used as the material,and the two-factor split zone test design was adopted.The planting density(plants/hm~2)was the primary area,and the plant spacing(cm+cm)was the secondary area.2017 planting density was 45000(A1),67500(A2)and 5 row spacing configurations ie 60+60(B1),80+40(B2),80+80(B3),110+50(B4),100+100(B5);2018 planting density was 45000(A1),67500(A2),90000(A3)and 4 row spacing configurations,ie 60+60(B1),80+40(B2),80+80(B3),110+50(B4).The effects of planting density and plant spacing on summer maize population structure,dry matter accumulation,stem lodging resistance and female and male panicle differentiation characteristics,yield and its composition were studied,in order to provide a theoretical basis for the mechanized and high-yield and high-efficiency production of summer maize.The main results are as follows:1.The density increased,the plant height,ear position and center of gravity increased,the stem diameter decreased,the leaf area index increased significantly,the angle between stem and leaf and opening angle became smaller,and the leaf orientation value became larger,but the population light transmittance still decreased,the extinction coefficient increased.At 45000 and 67500 plants/hm~2,60cm equal row spacing treatment,which of the stem was larger,the plant type was more compact and the inter-row light transmission condition was better.While at 90,000 plants/hm~2,the wide and narrow row treatment of110+50cm was more favorable to improve middle and lower ventilation and light transmission conditions.2.The planting density increased,the dry matter accumulation and accumulation rate per plant decreased,but the population dry matter accumulation increased,the average of two years,from 45000 to 67500 plants/hm~2,the dry matter accumulation at the silking and maturity increased by 29.57%and 30.44%,respectively.At 45000 and 67500 plants/hm~2,the average row spacing increased,the population dry matter accumulation decreased in all periods,while the overall showed increasing trend at 90,000 plants/hm~2.Compared with the corresponding wide and narrow row treatment,the population dry matter accumulation increased at each period,but B4(110+50cm)treatment was higher than B3(80+80cm)treatment at 90,000 plants/hm~2,especially the middle and late growth stage.3.Densification made the stem slender,the per unit internode dry weight,internode crushing and compression strength decrease,the mechanical strength and toughness become weake,the lignin and cellulose content reduce,and field lodging rate increase.At45000 and 67500 plants/hm~2,the equal row spacing is better than the corresponding width and narrow row,and the strongest stalk resistance was in 60+60cm,while at 90,000plants/hm~2,110+50cm performanced best.Therefore,the medium and low density(45000and 67500 plants/hm~2)was an important measure to improve the lodging resistance of maize.But at high density,it increased by increasing wide rows to improve the ventilation and light transmission conditions in the field.4.With the increase of density,the tassel main branch length and the spikelets pairs number decreased,the total florets of female spikelets,the silken florets number,the normal fertilized florets number and fertilization rate of per plant also decreased,while the degraded florets number,the abortive flowers number and the abortive florets rate increased,the ear traits of maize became worse,the maize yield increased first and then decreased,and the yield of 67500 plants/hm~2 was higher than that of maize.In 2017,the67500 plants/hm~2 density was significantly increased by 18.51%compared with the 45000plants/hm~2 density.In 2018,the yield of 67500 plants/hm~2 density was significantly increased by 15.58%and 15.98%compared with the 45000 and 90,000 plants/hm~2densities respectively.At 45000 and 67500 plants/hm~2,the average row spacing increased,the grain yield decreased,and the 60+60cm treatment yield was the highest.When the weak light and rainy conditions were more severe in 2018,at 90,000 plants/hm~2,the average row spacing increased,the grain yield increased and the 110+50cm treatment yield was the largest.In summary,two-year field experiments showed that the summer maize production in the middle hilly area of Sichuan Province should be properly reduced row spacing and increased plants.It was suggested that the density of 67500 plants/hm~2 combined with60cm equal row spacing should be used to increase the maize yield,improve the plant type structure and the ventilation and light transmission condition in the field,promote the young panicle differentiation,enhance the resistance to lodging,and also benefit to mechanization harvest in row. |
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