根钻不同取样法对估算根系分布特征的影响

摘要

Soil coring is one of the most labor-saving and accurate sampling methods in obtaining representative data to estimate the total root value,but lacks a corresponding accuracy analysis.Sampling at three holes has been widely adopted in the literature,but our experiment employed a higher-density coring method to acquire cotton (Gossypium hirsuturn) roots.Root dry weight was chosen to study the accuracy of three,five and seven holes respectively.Five holes give better estimates of total root dry weight with less work while three holes could be representative of the soil surface (<30 cm),but had a wide deviation below 30 cm depth,especially in the bare rows,which had low coefficients of determination and failed to reach a level of significance.The rational sampling method is to collect samples from two holes,one hole,one hole at bare,narrow and wide rows respectively when considering both precision and time consuming labour.The root dry weights in a vertical direction were single-peak curves,and dropped sharply above the 40 cm soil layer,but were flat below 40 cm although there was a small increase in the 70 - 90 cm layer.Root dry weights were heavier in wide rows than in bared rows with respect to horizontal distribution.%利用根钻法得到的代表性值估算根系整体值的问题尚未得到解决.针对文献中普遍采用的3孔取样法,本研究采用根钻加密采集棉花根系,利用根系干重分析了水平方向取3孔、5孔和7孔条件下计算单株根系干重的精确性.结果表明在水平方向上取5孔能较准确的估算单株棉花的总干重；取3孔仅在表层具有较好的代表性,对裸行30 cm土层以下根系干重不能准确描述,其决定系数低,且未达到显著水平,对于根系的估算有较大的偏差；在裸行、窄行和宽行分别取2孔,1孔和1孔是保证准确度前提下最为省力的取样方法.根系干重在垂直方向上呈单峰曲线,40 cm土层以上,根系干重急剧下降,40 cm土层以下变化区域缓和,在裸行70～90 cm处有小幅度的增加；在水平方向上宽行根重大于裸行根重.