| The field experiment with summer sweet corn hybrid Tiandan 8 were carried out at Wuqiao experiment station of China Agricultural University in 2004. The effects of different plant density (45000, 60000 and 75000 plant/hm~2) and different nitrogen application rates (0, 120 and 240kg N/hm2) on fresh cob yield and its components, formation and regulation of appearance quality and nutritional quality in summer sweet com were systemicly studied. The results showed that:1, Fresh cob yield was apparently affected by application rate and plant population, and yield of fresh cob was apparently promoted by nitrogen application. To obtain the highest fresh cob yield , the optimum nitrogen application is 175.8kg/hm~2 under middle density, the yield increased with the increment of plant population, and there were not apparent different between middle and high density. The output percent of stem-sheath store matter as the index to evaluate the coordination of source and sink.2, Correlation analysis showed that the quadratic curve correlation existed between C/N and cob yield, it was obtained that at five-leaf, seven-leaf, ten-leaf, silking, 11d after silking and harvest stage, the best C/N value were respectively 0.93, 1.59, 1.01, 1.01, 2.13 and 1.42.3, Formation of ear length and width went through the whole developmental stage of ear, and the course could be expressed by Logistic equation. The ear length and width could achieve the highest increase rate at pollination and tasselling respectively. Spikelets per ear reached to maximum at tasselling stage, and then the fertile grains increased after silking stage. The effect of nitrogen application on weight per ear was the most apparent difference under 75000 plant/hm~2.4, To obtain the best ear characters and their uniformity, the optimum plant density is 60000plant/hm~2, the optimum nitrogen application is 162.1kg/hm~2 under middle density, during different development stage, the best C/N value were 1.27-1.63, 0.80-1.38, 0.81-1.07, 0.69-0.90, 1.39-1.71, 1.08-1.17, respectively. Plant density have higher effect on ear characters than nitrogen application.5, In 4-19 DAP, fresh grain size, 100-grain fresh weight and grain filling rate increased very fast, and which were higher in nitrogen application treatments. Grain filling was promoted by nitrogen application, but the effect was different under different density.6, Grain sucrose, soluble total sugar and starch content in sweet corn achieve the highest increase rate around at 12DAP, 15DAP and 12DAP respectively, gain protein and amino-acid content decreased progressively, sucrose , soluble total sugar, protein and starch weight per grain achieve the highest increase rate all around at 9DAP, but amino-acid weight per grain achieve the highest increase rate around at 13DAP. Different treatments have different effect on nutritional quality, nitrogen application have higher effect on gain protein, starch and amino-acid content than plant density; plant density have higher effect on gain sucrose and soluble total sugar content than nitrogen application.7, The highest content of gain sucrose , soluble total sugar , protein and starch could be achievedunder low density, but the difference between low and middle density wes not apparent ; while the highest content of gain amino-acid could be achieved under middle or high density. To obtain the best nutritional quality, the optimum nitrogen application is 125.8kg/hm~2 under middle density, during different development stage, the best C/N value were respectively 1.35-1.40, 1.17-1.25, 1.02-1.03, 0.62-0.71, 1.55-1.72, 0.98-1.02.8, Consequently, to obtain the unification between high yield and good quality, under the conditions of this study the optimum plant density is 60000 plant/hm2, the optimum nitrogen application is 120kg/hm2 to 180kg/hm2 under this density, it was obtained that at five-leaf, seven-leaf, ten-leaf, silking, lid after silking and harvest stage, the best C/N value were 1.27-1.63, 0.80-1.38, 0.81-1.07, 0.62-0.90, 1.39-1.72, 0.98-1.17, respectively. |
PDF Full Text Request