Effect Of Planting Densities And Pruned Methods On Population Quality Of Cotton In The Central-South Region Of Hebei

Using insect-resistant transgenic cotton Nongdamian 8 as material, six planting densities levels (1.5,3.3,5.1,6.9,8.7,10.5×104 plants /hm2) with conventional pruning treatment and three densities levels (3.3,5.1,6.9×104 plants /hm2) with simplification pruning treatment were conducted. Some population indice were studied to reveal the effects of planting densities and pruned methods on population quality of cotton.. The results showed that:1 Plant height and stem diameter decreased with the increase in planting densities. At the same planting density, the pruned methods has no obvious effect on plant height and stem diameter.2 Dry matter accumulation of the aerial part of cotton at the whole stage was well fitted by the logistic equation. The whole dry matter accumulation in group of high density is more than that in group of low density, and more in group with conventional pruning than that with simplification pruning. High density and simplification pruning can increase the maximum growth rate of drymateer accumulation, make it appear 5-11 days early and extend its duration.3 High density and simplification pruning can boost the maximum leaf area index, make it appear 13 days earler than other treatments and extend its function period. Light intensity decreased with the increase of planting density.4 On the time distribution of bolls, with the density increased, the pre-summer boll ratio and autumn boll ratio increased and the summer boll ratio decreased in conventional pruning treatment. The pre-summer boll ratio and autumn boll ratio is lower and the summer boll ratio is higher in simplification pruning treatment than that in conventional pruning treatment. On spatial distribution of the bolls, as the density increased, the medium-inferior boll ratio increased and the ratio of the bolls in nourishing shoot decreased. High density and simplification pruning promote the bolling center shift to the under parts. As the density increased, internal surround boll ratio increased and the external boll ratio decreased.5 Both the ratio of fruit nodes to brances and the ratio of bolls to leaf area decreased as the density increased, and it was higher in conventional pruning treatment than that in simplification pruning treatment. Both the maximum value of the ratio of fruit nodes to brances and the ratio of bolls to leaf area appear in the treatment with the planting density of 1.5×104 plants /hm2, the maximum value are 5.8 and 30.74 / m2 respectively. 6 The amount of roots wound flowing decreased with the increase of planting density. The curve of roots wound flowing in conventional pruning treatment had two peaks, one occured at full-bloom stage, the other occured at boll opening stage. The curve of roots wound flowing in simplification pruning treatment had only one peak, which occured at full-bloom stage. The wound flowing occupied by each boll was less in conventional pruning treatment for dates when the planting density was lower and more for date when the planting density was higher, and it changed as low-high-low in simplification pruning treatment.7 The chlorophyll content of the main stem function leaf changed in single peak trend at different stages. The chlorophyll content reached the maximum value at the stage between full flowering and bolling when that of conventional pruning treatment was higher than that of simplification pruning treatment. The influence of densities on chlorophyll content was small. The soluble protein of the main stem function leaf reached the highest at the prosperous bud stage, and intended to decrease with the densities rising. But there were no significant differences in the soluble protein content of the main stem function leaf under different densities or pruned methods. Also, there were no significant differences between the soluble protein content of efficient leaf and that of inefficient leaf.8 The content of total soluble sugar in the main stem function leaf reached the maximum value at the prosperous bud stage. The density and pruned methods had little influence on the content of total soluble sugar. The content of total soluble sugar in efficient leaf were significantly lower than that in inefficient leaf. The net photosynthesis rate of leaf of main stem have one peak at the full flowering stage, and it was no significant difference among desity treatments and pruned methods treatments. But the net photosynthesis rate of efficient leaf were significantly higher than that of inefficient leaf.9 With the increase of planting desity, the seed cotton yield ascended first and then descended under conventional pruned methods, while descended under simplification pruning treatment. Compared with the conventional pruning treatment, remain leafy shoot can produces higher yield when the density is lower and produces lower yield when the density is higher. The maximum yield of cotton is 3542.9㎏/ hm2 which appears in the conventional pruning treatment with the 6.9×104 plants/hm2density, the yield of the simplification pruning treatment with the planting density of 3.3×104 plants /hm2 is 3504.3㎏/ hm2. The density and pruned methods has no obvious effect on Fiber Quality.The density and pruned methods can effect every index of population quality. In this experiment, the results showed that only the bolls number was significantly positive related to yield. Other indexes were regarded as inter-constraint measures, which have the relative optimum value in different population.