| In the experiment, Zhengdan958(close planting and early maturing maize cultivitar) was chosen as the material, by taking the maize production fields of Zaohua Town, Shenyang province and Cainiu town Tieling country as the research object in2011-2012, estabilished the experiment of sowing date and planting density in high yield population, divided as main test and auxiliary test, to investigate the relationships of yield and sowing date, yield and plant density, and explored the mechanism of coordination of water and heat, to clear the main limiting factors of obtain high yield through planting density and the effective using of water and heat, and illustrated the effect of sowing date and planting density on premature and lodging in maize. Main research results were as follows.1.The key limiting factor which affected the yield of maize was rainfall in south of Northeast China, the effective accumulated temperature after silking was the main factor to affect car barren tip and unfilled grain, and the rainfall after silking was the key factors which affected kernels per row and grain depths. Under the source of light and heat in Northeast China, the appropriate sowing dates were from25th April to10th May, and appropriate planting density were45000～67500plant·hm-2. The annual yield and yield component performance of different sowing date and planting density, the yield of early sowing date and middle planting density was the highest for two years, to compared with planting density, sowing date was the most important factor which affected yield, the main factor to evaluate yield was though early sowing in optimum time increasing ear number, enhancing grain weight per1000.2. Early sowing could prolong the duration time of growth and development of maize; With the delay of sowing date and the acceleration of growth progress, the temperature of late sowing date was relatively higher, the duration time of sowing-emerge and emerge-jointing were shorten. With the delay of sowing time, the emerge time of population dry matter accumulation shift to an earlier date, and accumulated this trend. The dry matter (DM), dry matter accumulate rate (DMAR) and crop growth rate of late sowing time in earlier growing stage was highest, then was the middle sowing date, and the early sowing date was the lowest; In late growing stage, the order of DM and DMAR was early, middle and late. Compared with planting densities, the order of DM, DMAR, CGR was high plant density, middle density and low density.3. Plant height, spike position height and the length of second internode and spike position height coefficient were increased with the delay of sowing date, but stem diameter and coefficient of-stem diameter were decreased, and significant differences were exicited. Compared with planting densities, plant height, spike position height, the length of second internode and spike position height coefficient were increased orderly with planting densities, but stem diameter and coefficient of stem diameter were decreased. The regular of leaf weight ratio (LWR) was unimodal curve, reached a maximum value then decreased gradually, and became steady until later growth stage. In the sowing dates treatments, with the delay of sowing time, LWR, leaf area ratio (LAR) and specific leaf area (SLA) were decreased sequentially; Compared with planting densities, the order of LWR was high density, middle density and low density, and there were not significantly differences; LAR and SLA were decreased with planting density increasing, there were significant differences among different planting densities.4. The change of LAI was significantly affected by sowing date during silking stage. With the delay of sowing date, LAI decreaced mostrapidly, The emerge time of LAImax、 TLAImax、TVmax and duration time of TLAI>4were sequenced as ES>NS>LS, but Vmax was increasing trend with the delay of sowing date; for early sowing date, the LAD for all growth stage and the ratio of LAD after silking were higher than normal and late sowing time; There were significant effect of planting density on the LAI of maize population, the LAI of maize population was decreased with the increasing of planting densities, the LAI of D3decreased rapidly. The duration time of LAImax、Vmax、TVmax and TLAI>4were increased with the increasing of planting densities, in opposite, TLAImax was decreased, high planting density did not contribute to the accumulation of LAD.5. The photosynthetic parameters of early sowing date, such as net photosynthetic rate and its light response curve, transpiration rate and its light response curve, intercellular CO2concentration (Ci) and stomatal conductivity (Gs), was higher than normal and late sowing date, but water using efficiency (WUE) was lower. The photosynthetic parameters and net photosynthetic rate and its light response curve, transpiration rate and its light response curve, light using efficiency (LUE) and water using efficiency (WUE) of middle and low planting density was higher than high planting density. Reasonable planting densities and sowing date could established a rational canopy structure, prolong the fuctional time of leaf, enhanced the light using efficiency and water using efficiency.6. Early sowing date and low planting date could enhance the trend of maize premature. The advance time of sowing date could increase Fo, and decreased photosynthetic chemical efficiency of PS Ⅱ reactive center, the Fv/Fm of early sowing time was lower than nomal and late sowing time; Too high planting" density would destruct PS Ⅱ reactive center, increase Fo, and accelerate the premature of leaf. The regular of concentration was, with the development of growth progress, the concentration of Chl(a+b) increased firstly and then decreased, the peak value emerged about day after silking. The decreased rate of Chl(a+b) concentration for ES was higher than NS and LS; With the increasing of planting density, the concentration of Chl(a+b) decreased rapidly. SOD was decreased with the delay of time, ES decreased strongly; Compared with planting densities, the SOD activity was decreased with the increasing of planting density, the SOD activity of early sowing date and high planting density was decreased, but MDA was opposited. Average grain filling rate was the main factor which affected kernel weight, the duration time of grain filling peak value was the submain factor to affect kernel weight at the above position of ear, the duration time of was the submain factors to affect the kernel weight of the middle and low position. Early sowing date could prolong the continous increasing time of grain filling, contribute to the effective accumulation of dry matter, and result to a relatively large grain dry weight.7. The grain filling rate of normal sowing time was highest, improved the average grain filling rate, and prolonged the duration time of grain-filling peak value period; the duration time of grain filling, maximum grain-filling rate, average grain-filling rate, and duration time of grain filling peak value period were all decreased, resulted the lowest kernel dry weight finally. Compared with planting densities, with the increasing of planting densities, the duration time of grain filling was prolonged, but maximum grain filling rate, average grain filling rate, and duration time of grain filling peak value period were all decreased, resulted the dry weight of final grain was decreased with the increasing of planting densities.8. Late sowing is not conducive to the accumulation of grain protein and fat, proper early sowing could increase grain oil content, the suitable sowing period with low planting density can improve the content of grain protein and starch. Late sowing with low density promoted the increasing of fat content, planting density is not conducive to the accumulation of fat in grain.9. The effect of planting density on the vertical distribution of root system is higher than that of sowing date.0-45cm soil layer of root dry weight proportion for LS treatment, accounting for87%of the whole soil profile root dry weight, NS and ES were81.45%and73.83%, in case of heavy rain and strong wind weather late sowing prone to lodging; The roots of D3was less in0-30cm distance of soil root distribution and the lateral root center distance, root distribution is relatively high below60cm, the upper root weight would be decreased if there were too high density, but the total root amount of high planting density is relatively small, root support weakened, easy to occur the risk of lodging. The bleeding intensity in early sowing was higher than that in the normal and late sowing date, The root vigor of early sowing was strong, could support plant aboveground; The bleeding intensity became weaker with the increase of planting density, Too high planting density is not conducive to the growth of root, so root vigor was decreased.10. Soil water content was increased with the delay of sowing date and the decrease of planting density. The soil moisture in different planting density was different, quick change layer (10-20cm) soil moisture content increased with the increasing of planting density, buffer layer (20-70cm) and relatively stable layer (below70-100cm) water content with soil volume was opposite trends from rapid change layer, it reduced along with the increasing of planting density. |
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