不同砍种方式对木薯幼苗期生长的影响

Effects of Different Seed-stem Cutting Methods on Cassava Growth at Seedling Stage

为了探讨不同砍种方式对木薯幼苗期生长的影响,为种植木薯提供科学指导。并验证环割或环剥能增加木薯苗期生根位置和生根数的假设。在沙床内种植木薯,设置直切、斜切、环剥等7种砍种方式,在12~14 d和33~35 d观测地上部重、根重、根数、长度、单位长度根重等指标。并通过专家调查法调查了各观测指标的权重,并将权重与各指标归一化后的值相乘,之后将所有指标得到的该乘积相加,得到各个砍种方式的评价系数。结果表明：各处理2次采样的各指标基本都有显著差异。环剥处理比直切增加了生根位置和生根数,但差异并不显著;木薯种茎重与各生长指标的相关分析表明,木薯种茎对12~14 d的生长影响较大;但随着木薯的生长,在33~35 d时,木薯种茎与各生长指标的相关性不显著,很可能是14 d的施肥导致的。通过专家调查法调查并计算各指标的权重,得到各种处理方式对木薯生长的评价系数大小为：环剥1 cm〉环割2 mm〉锯切〉环剥2 cm〉斜切（1~1.5 cm）〉直切〉斜切（2~3 cm）。研究中环剥1 cm的砍种方式是最优的,其在环剥处和种茎基部均有生根,符合假设。而斜切（2~3 cm）最不利于木薯生长。

The effects of different seed-stem cutting methods on cassava growth at seedling stage were studied so as to provide scientific guidance for cassava planting. The hypothesis that girdling can increase rooting zone and root number of cassava at its early growth was testified.Cassava seed-stem was planted in sand bed with seven treatments： Ⅰ vertical cutting with knife（smooth cutting surface）; Ⅱ Vertical cutting with saw（rough cutting surface）; ⅢGirdling（ 2 mm）; Ⅳ Girdling（1 cm）; Ⅴ Girdling（2 cm）; Ⅵ Oblique cutting（1~1.5cm）; Ⅶ Oblique cutting（2~3 cm）. At 12~14 d and 33~35 d, the root number, root length, weight of roots and aboveground parts, and so on, were observed. Each index weight was investigated by the expert-investigation method, and was multiplied with its corresponding normalized index. The ＂ Composite index＂ of the treatment was the sum of the above mentioned product of all indexes. Results showed that： 1） There was significant index difference between the two time measurements in each treatment. The root rate in girdling was higher than that in vertical cutting, but the difference was not notable. 2） The weight of seed stem was significantly correlated with each observed index at 12~14 d, but not significant at 33~35 d,probably due to fertilization input at 14 d. 3） The sort of the calculated ＂Composite index＂ of the treatment was： Ⅳ〉Ⅲ〉Ⅱ〉Ⅴ〉Ⅵ 〉Ⅰ〉Ⅶ. In conclusion, girdling（1cm） is the optimal way for cassava growth at the first period, while the oblique cutting（2~3cm） is the worst.