| The effects of sowing date, planting density and nitrogen applying rate on the time and space distribution of setting rate and yield components were studied by using hybrid cotton variety-Nongza 62. The main results were as follows:1. The ratio of pre-hot-seasonal bolls to total number of bolls decreased with delay of sowing date, increased slightly with the increasing of planting density, decreased as N application higher or lower than optimal application rate. The ratio of autumn boll to total bolls increased with the delay of sowing date, decreased with the increasing of planting density (but while planting density was high enough, the ratio increased to some degree), increased as the increasing of N application. The ratio of hot-seasonal boll to total boll was highest, the average value of different treatments is 62%.2. The boll-setting number showed the change trends of "fewer-more- fewer" from bottom to top fruiting branches. The bolls of fruit branches on node 4-10 are higher than others. The vegetable branches fruited 5.31 bolls per plant. The treatment 3 had the highest boll number on vegetable branch, reaching to 10.8 per plant. As sowing date was delayed, the boll-setting number of lower fruiting branches increased, while the bolls of middle-top branches decreased correspondingly, the number of vegetative branches and bolls also decreased . With the increasing of N application, the bolls of upper branches increased, but the bolls of middle and lower branches decreased correspondingly. Under higher density, the bolls of upper and lower branches was higher, the bolls of middle branches was lower. At horizontal level, bolls at the 1st, 2nd and 3rd fruiting positions of branches were more, hereafter, decreased gradually, the boll-setting of 6th sympodial node was very low, but under the lower density and higher N application, the boll-setting of peripheral sympodial node from middle and lower branches increased. No significant effects of sowing date on boll-setting of beyond 4th fruiting node was found, but the effects of sowing date on the boll-setting of vegetative branches was significant. Under the condition of early sowing or lower density and higher N application, the vegetative branches fruited more than others.3 The regression model between cultivation factors and yield was established. The regression model between lint yield (Y), sowing date (XI), planting density (X2), N application rate (X3) was as below: Y=146.89-2.33X1-3.16X2 + 9.30X3-7.12X12-6.69X22-12.20X32-t-0.79X1X2+0.45X1X 3 -2.01X1X3. Simulating precision was higher, the value of x 2=12.27, no significant difference and the equation was effective. The results showed that sowing at April 17th-18th, 1552 plants/666 7mJ, 17.65 kg N/666.7m2, the highest lint yield 149.2 kg/666.7m2 can be obtained.4 The number of bolls was increasing significantly with the decreasing of planting density. The bolls per plant was increasing with the increasing of N application, but if N application was higher than certain amount, the bolls per plant decreased. The early sowing treatments had higher boll number per plant compared with that of late sowing treatments. The total number of bolls was affected by three tested factors significantly, which was higher at more N application, the lowest at zero N treatment. With the N application more than certain amount, the total number of bolls decreased. The average individual boll weight per plant was increasing with the increasing of N application and delay of sowing date. There was no significant effects of planting density on individual boll weight. Lint percentage was rather stable, rarely affected by cultivation.5 Vertically, the contribution rate of middle fruiting branches to lint yield was highest, all of the treatments showed no difference, averaged 33.37%, which was rarely affected by cultivation factors. The average contribution ratio of leaf branches to lint yield was 11.37%, the highest was 18.57%(5* treatment), the lowest was 1.68%(2<>d treatment). Horizontally, die contribution rati... |
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