Effects of Planting Density on Yield and Source-sink Characteristics of Sweet Potato[Ipomoea batatas (L.) Lam]
[Objective] The aim was to resolve the issue of sparsely planting (37 500-40 500 plants/hm2) of sweet potato in hilly areas.[Method] The starch-oriented Jishu No.21 and raw-eating oriented Jishu No.22 were studied to explore effects of planting density on yield and sink and source characteristics of sweet potato.[Result] Leaf area index of Jishu No.21 and Jishu No.22 were increasing upon planting density.Leaf area index of the same planting density showed a single-peak curve.Specifically,leaf area index grew fast during the 40th-80th d after planting,and reached the peak on the 80th d after planting,followed by decreasing.What's more,ventilation and sunshine transmission both declined upon planting density,as well as the number of leaf,the number of branch,the length of vine,dry and fresh weights of stem and leaf.When planting density exceeded 75 000 plants/hm2,the yield of sweet potato dropped dramatically.Besides,the optimal planting density tended to be volatile upon cultivars.For example,the range of 45 000-60 000 plants/hm2 is the optimal planting density of Jishu No.21 and the range of 60 000-75 000 plants/hm2 is the optimal planting density of Jishu No.22.[Conclusion] It can be concluded that rational planting densities would well coordinate sweet potato growth of ground parts and underground parts to get a high yield by providing a rational group structure.Considering the optimal planting density differs upon cultivars,it is necessary to take genotype,environment,soil fertility and planting density into consideration in determining planting density.
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