Studies on Characteristics of Morphotogy and Physiology of Summer Maiz Hybrids with High Yield Potential in Huanghuaihai Area
|School||Henan Agricultural University|
|Keywords||Huang-Huai-hai Summer corn Physiological characteristics Morphological characteristics|
In this paper,22 maize varieties, being widely planted in Huang-Huai-hai ecological zones of summer maize, were planted in field of Xunxian Agricultural Insititute from 2007 to 2008. Using a kind of statistical analysis methods, those varieties were studied on yield and its composition, dry matter weight, leaf area index, photosynthetic potential, net assimilation rate, crop growth rate, plant nutrient uptake efficiency and nutrient use efficiency, chlorophyll content, photosynthetic rate and grain filling rate. The aim was to screen out corn hybrids with high and stable yield and provide a scientific basis for the screening and generation of super high-yielding summer corn. The main results of the study were as follows:1. Corn yield lies on three elements constituting yield such as ear number per unit area, grain number per ear and 1000-grain weight. Ear number per unit area was depend primarily on the planting density of variety, while grain number per ear and 1000-grain weight lies on its characteristics and self-regulation ability. With the coordination of the three elements, the theoretical maximum yield could be obtained. Among the three elements, yield is contributed primarily to ear number per unit area. However,1000-grain weight and grain number per ear were different for yield forming in varying planting densities. To improve the yield was mainly depend on 1000-grain weight in the density of 60000 plant/hm2, while it was mainly depend on grain number per ear in the density of 52500 plant/hm2. The compositions of yield were also interacted with each other. So, the main element must be grasped to reach the high yield potential. The result of test showed that, the yield compositions of corn with high yield was 207g of grain weight per ear,368 g of 1000-grain weight and 3500 grain/m2. Therefore, high-yield corn hybrids should have the dual advantages of unit area of higher grain number per area and grain weight. In addition, the lodging seriously affected maize grain filling and the 1000-grain weight, led to the decrease of yield. Therefore, lodging resistance has become a major objective of maize breeding. In the Huang-Huai-hai summer maize area, maize varieties with moderate and big ear, density-enduring, lodging and disease resistance, and good fecundity should be treated as the breeding goal.2. The performance of leaf area of high-yielding maize hybrids changed as formerly fast, then steady, slow declining finally. High-yield populations with different planting densities should have a potential leaf area index. Too big LAI affected photosynthesis of maize. The suitable LAI and photosynthetic potential with the density of 60000 plant/hm2 was 4.75 and 32x106 m2·d/hm2. The result showed that, the same change of the two groups with high and low density was the leaf area growth rate during milky-silking stage. And the leaf area in the period is the key element for the yield establishment. The photosynthetic potential in pre-silking period of varieties with low-density had a great impact on the yield establishment, while the photosynthetic potential in post-silking period of varieties with high-density had a great impact on the yield establishment. However, the corn yield was mainly come from the leaves photosynthesis in post-silking period. Therefore, varieties with high density could reach higher yield easily. Suitable leaf area, high photosynthetic potential and high proportion in post-silking period were essential to corn hybrids with high yield potential. Corn hybrids with high yield potential had not only a bigger suitable LAI, but also a reasonable population dynamic. In tradition, it also had a little aging rate of LAI and long duration of largest leaf area.3. Grain-filling period is the critical growth stages for growth and development of maize. Corn yield mainly affected by dry matter accumulation in grain-filling period. Grain-filling rate were controlled by genotype and environment. Dry matter accumulation in grain-filling period was determined by grain-filling length and rate. The characteristics of high-yield corn hybrid were higher net assimilation rate and crop growth rate from the milky stage to dough stage, higher net assimilation rate from dough stage to ripening period, slowly aging rate, bigly rate of dry matter accumulation and grain-filling strength after silking. The results showed that, grain-filling after 30-50 d of varieties with 52 500 plant/hm2was more important to yield establishment. The grain filling of 30-40 d and 50-55 d of varieties with 60000 plant/hm2 was more important to yield establishment. In the experiment, late-harvest 10 d could increase 12.7%～15.5% of corn yield. Therefore, late-harvest of corn (after 8-10d of corn husk yellowing) should be promoted vigorously in summer maize ecological zone of Huang-Huai-hai.4. Larger grain-leaf ratio of maize varieties was help for high yield. In the study, the grain-leaf ratio of corn hybrids with high yield was 716 grain/m2 and 266 g/m2. The grain-leaf ratios of Xundan 18 and Denghai 602, the highest yield variety in different densities groups, respectively, all were the highest. It was also improved that higher grain-leaf ratio was vital to obtain high yield.5. The nutrient contents of N, P and K in each organ of maize in different growth stages were different. There were greatly different in nutrient contents of each organ among different maize varieties. There were also different in the accumulating content of N, P and K of different maize varieties in different growth stagea. In total, the results showed that, there were two peaks for absorbing nitrogen of maize plant in the whole growth process. The first was jointing stage to the big trumpet period. The other was from 20d to 40d after silking. There was only one peak for absorbing P and K of maize plant in the whole growth process. The peak period of P was from silking to 20d after silking. The absorption and accumulation of P in maize plants was the most at this stage. The peak period of K was from jointing stage to the big trumpet period. At this stage the absorption and accumulation of K in maize plants was the most. The absorption and accumulation of N, P and K in maize plants before jointing stage were the least. Thus, the absorption and accumulation of N, P, K in maize plants were in lower level before the jointing stage. Therefore, to apply a part of base fertilizer could promote the seedling growth. The demanded quantity of N, P, K were larger from the jointing stage to the big trumpet period and filling stage, especially from the jointing stage to big horn stage. Thus, fertilizer should be top-dressing in the jointing stage to meet the needs of maize growth. After silking, to top-dressing grain fertilizer was helpful to increase the yield. At the same time, the regulation of absorption and accumulation of N, P, K of different maize varieties in different growth stages should be kept to fertilize rationally, to achieve its maximum utilization rate, and to obtain high-yield.6. High-yielding hybrids should have the characteristics of compact plant type, suitable plant height and ratio of ear and plant height, strong lodging and disease resistance.