Study On Root Characteristics In High-yield Maize Under High-planting Density

In maize(Zea mays L.),rational root structure promotes high grain yield under dense sowing conditions.This study was conducted at Qitai Farm in Xinjiang,China,in 2019 and 2021.A traditional wide and narrow row planting pattern was adopted,with wide row of 0.7 m and narrow row of 0.4 m.Cultivar DH618 was suitable for dense planting production and has a yield potential of 22.5 Mg ha-1,and cultivar SC704(15 Mg ha-1)was less tolerant to high density were selected for study of the root structure and distribution characteristics under high-yield and high-density planting conditions.The results showed that the number of grains per ear decreased by 19.8%,1000-grains weight decreased by 13.0%,and the number of ears harvested increased by 37.2%,the yield of DH618 increased significantly after densification,while SC704 had a significant decrease.The results of root structure under 12×104 plant ha-1 density were as follows:(1)The root structure of DH618 was well developed at that planting density,and the root dry weight(RDW)was 17.49 g plant-1 and 14.65 g plant-1 at the silking and maturity,respectively;these values were 7.56%and 11.86%higher,respectively,than those of SC704;At silking and maturity stages,the root-shoot ratio of DH618 were 0.176 and 0.046,respectively(25.6%and 15.2%higher,respectively,than the root-shoot ratio of SC704).The root lengths of DH618 were 239.72 m plant-1 and 199.04 m plant-1 at the silking and maturity stages,respectively;these were 16.45%and 25.39%higher,respectively,than the root lengths of SC704;The surface area,volume and average diameter of root system were 0.47 m2,44.3 cm3 and 0.46 mm respectively at the silking stage and 0.31 m2,35.6 cm3 and 0.40 mm respectively at the mature stage.(2)DH618 had a high proportion of root distribution in deep soil.At the silking stage,the proportions of RDW at soil depths of 0-10,10-20,20-40,and 40-60 cm were 66.29%,11.83%,16.51%,and 5.38%,respectively,for DH618;over the 20-60 cm soil layer,this was an average of 4.04%higher than the RDW of SC704.At maturity,the proportions of RDW at soil depths of 0-10,10-20,20-40,and 40-60 cm were 61.40%,11.19%,17.19%,and 10.21%,respectively,for DH618,which was an average of 9.59%higher than that of SC704 over the 20-60 cm soil layer.At maturity,DH618 roots were mainly distributed in the narrow rows,accounting for 72.03%of the root structure;this was 9.53%higher than the roots of SC704.This study indicated that the maize hybrid DH618 had a more developed root structure with increased root distribution in the deep soil and narrow rows under high-density planting compared to cultivar SC704,contributing to high grain yield under dense planting.(3)The root population increased significantly under high-planting density;At silking and maturity,the root weight densities(RWD)of DH618 were 471.98 g m-3 and 382.98 g m-3,respectively(5.18%and 5.97%higher,respectively,than the root weight densities of SC704).The root length densities(RLD)were 0.58 cm cm-3 and 0.46 cm cm-3 at the silking and maturity stages,respectively,and these were 16.86%and 17.08%higher,respectively,than the root length densities of SC704.