Tetraploid Robinia pseudoacacia was taken to measure the dynamic change of biomass and nutrition to determine the best harvesting time in growing season.After the leaf chemical content of the 1-year-old and 2-year-old plant of tetraploid R.pseudoacacia were analyzed,the chemical content of leaf,stem and whole plant of the 3-year-old plant were also analyzed as well as the height,basal diameter,leaf biomass and stem biomass.The results showed that both leaf biomass and stem biomass increase rapidly from May to June,while it almost stops growing between June 25 and August 10,then it increases rapidly again from August 10.A similar pattern was obtained for both height and basal diameter growth.The entire analyzed chemical content is similar in the different years.The CP content is highest in leaf and lowest in stem.Moreover,CP of three-plant parts decreases rapidly from June to July,while it declines gradually from July to September.DM,NDF and ADF contents of all three-plant parts increase slowly during the growth stages,and the concentrations in leaf are the lowest,while those in the stem are the highest.Considering biomass and nutrition of both leaf and stem,late June is the best first harvesting time in a year.%为了更好地了解四倍体刺槐(tetraploid Robinia pseudoacacia)生长季节的生物量和营养质量分数动态变化,为确定其饲料林的最佳刈割时期提供理论依据,在测定1～2年生林分生长时期叶片营养的基础上,测定了3年生林分的株高、基径和叶质量、茎质量动态,并分析了此林分的叶片、茎杆和整株的营养动态.结果表明:叶片和茎杆生物量的变化与株高和基径生长动态相似,均在6月25日前增加迅速,然后进入缓慢生长期,最后从8月10日再次快速生长;不同年份的叶片营养质量分数具有相似的变化趋势；在整个生长过程中,叶片的粗蛋白质量分数最高,茎杆最低,且粗蛋白质量分数从6-7月份下降迅速,随后逐渐下降；叶片、茎杆和整株的干物质、中性洗涤纤维和酸性洗涤纤维质量分数在生长季节逐渐增加,而且均在叶片中质量分数最低、茎杆中最高.综合考虑叶片及当年生茎杆生物量和粗蛋白质的相互变化,确定四倍体刺槐第1次最佳刈割时期为6月下旬.
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