Research On Dense Planting Effect For Different Density-tolerant Corn And Rule Of Corn Density Tolerance Inheritance

Maize was a high and stable yield crop. However, contradiction between individual and population became more and more serious with breeding and production level developed, it was very hard to increase maize yield by exploiting individual productivity alone. Developing and extension of density-tolerant maize variety,depending population yield on increasing unit yield was an inevitable trend in increasing unit yield further.There were many uncertain factors to high density maize breeding and production. For example, request of soil fertility level, cropping pattern and planting density of high density variety, effect of planting density on different genotype variety when planting density enhanced, which traits could used to evaluate maize density tolerance? How maize density tolerance inheritance? etc. This paper designed different trials to answer the questions above. Hope to providing selective reference for high density maize breeding and guiding for production by cultivation experiment. Conversely, it would also promote maize breeding more pertinent, efficient and breed more excellent high density variety service for production by posing problems. The main results showed as follows:1. Effects of planting density on yield ie very big, yield may be increased obviously if planting density be increased suitably. Effects of planting density on characteristics finally reflects to the influence to yield and the directon of them on three factors of yield component is same,only different in level. Ear number in unit area of three varieties increased obviously along with density while grain number per ear and 1000-grain weight decreased and the degree was different in varieties. The high production forming process is intercoordination process among three factors of yield component.2.Effects of planting density on agronomic traits of different varietys were very complicated. Variation of plant height, ear insertion and ear rows were derived from varietys, planting density had little effect on them, so that 3 indices should not be considered deeply. Though the variation of ear length, ear diameter and kernels per row were derived from varietys, the 3 indices changed with the planting density increased, so that 3 indices should be considered properly. Effects of planting density on lodging rate, bare plant rate and anthesis silking interval (ASI) and bare top length were relatively strong, so that indices should be paid more attention and could be considered to be the appraising indices of density-tolerant variety.3. Different variety single leaf area and LAI assume the unimodal curve changed along with the birth time, but the different variety changing tendency was different. Leaf of LiaoDan 565 with no premature senescence after tasseling stage, duration of larger leaf area, LAD and NAR of LiaoDan 565 was relatively long, it was beneficial to maize kernel formation and filling. While Leaf of middle type variety LiaoDan 527 and thin density variety DanYu 39 would drop rapidly after tasseling stage, duration of larger leaf area was short. LAI increased along with the density increase. The increasing rate of LAI was bigest at jointing stage and droped at tasseling stage. Autoregulation ability of density-tolerant maize variety to different planting density was better than that of other varietys. Higher photosynthesis at high density treatment at late growth stage was one of reason of high yield. But photosynthesis potential of thin density variety was unreasonable with planting density increased, which leaded to the decrease of yield.4. Dry matter accumulation of density-tolerant variety increased with planting density enhanced in a certain range. That of thin density variety increased at the beginning, then decreased with planting density increased. The peak of dry matter production rate of density-tolerant variety LiaoDan 565 appeared at tasseling-milk stage, thin density variety DanYu 39 appeared from Tuba mouth stage to tasseling stages, which earlier than density-tolerant variety. That variation leaded to plant growing so fast at early growth stage, HI relatively low and yield decrease finally. Conversely, transportation and storage of dry matter of high density variety were relatively coordinate, which resulted in yield increase finally.5. There had big difference in genetic characteristic of many traits at high and low planting densities. If breeding selection was carried out at low planting density, the selected varietys often showed false appearance, or say, these materials would have no high density tolerance when planting density increased to a certain degree, those materials would even harder to breed density-tolerant variety. Therefore, the selection of density-tolerant variety should be carried out under a certain density pressure and different traits should be selected at different generation. Plant height, ear insertion , bare plant rate, 1000-kernel weight and plot yield should be selected at early generation, ASI, lodging rate, ear length, ear diameter, ear rows, kernels per row and bare top length should be selected at late generation.6.High density tolerance of maize varietys in LiaoNing province appeared increasing trend by evaluation of many typical high density tolerance varietys, which selected and introduced in the 1980s. The maize production level of LiaoNing province would go to a new step further by breeding and extension of density-tolerant varietys. The breeding efficiency of density-tolerant variety would be promoted by increasing planting density. Inbred lines 7029 and 7038 etc screened in this trial had better high density tolerance, which would play an important role in high density breeding.7. Different soil fertility condition needed different variety and suitable planting density. Density-tolerant variety obtained high yield when soil fertility level was better regardless of the density while thin density variety did low. Therefore, if the soil fertility condition was good we should choose density-tolerant variety to obtain high production. When the fertility was bad, we should not introduce density-tolerant variety blindly, thin density tolerant variety had good yield on the contrary. The soil fertility condition is good in LiaoNing province, so the planting density should be increased suitably in most areas.Cropping pattern had a great effect on yield. Conclusively, pattern of shorten row spacing and increase planting density obtained the highest yield, pattern of double lines at one width ridge ranked second, pattern of width and narrow row ranked between them, patterns of traditional and 2:0 planting obtained the lowest yield. Double lines at one width ridge and shorten row spacing and increase planting density patterns were beneficial to yield potential booming of LiaoDan 565 and LiaoDan 527. For increasing maize yield, suitable planting pattern and density should be established according to different genotype characteristics of varietys.