添加玉米秸秆对白浆土重组有机碳及团聚体组成的影响

摘要

研究添加有机物料后,土壤重组有机碳含量变化及其对土壤团聚体组成的影响,对于科学评价秸秆还田对土壤的培肥作用及其环境效应具有重要意义.采用室内培养试验,培养120 d,研究耕作白浆土耕层土壤和母质层中添加不同比例秸秆对土壤重组有机碳积累量、团聚体组成及各粒级团聚体中有机碳分布的影响.结果表明:随秸秆施用量增加,耕层土壤和母质的重组有机碳含量均呈同步增加趋势,耕层土壤和母质相比,重组有机碳增量差异不大,两者增量差值仅为0.34 g kg.,但两者的有机碳增率差异很大,耕层土壤仅为85.51％,母质则高达556.23％.说明在成土过程中,耕层土壤中有机质的累积会降低其固碳潜力,而在母质层中,其固碳“位点”处于“空置”状态,因此有很强的固碳潜力.同时,秸秆的添加,促进了土壤中小粒径团聚体(＜ 0.25 mm)向大团聚体(＞0.25mm)的转化,耕层土壤和母质土壤在秸秆添加量为3％和2％时大团聚体中有机碳的贡献率最高,分别为69.90％和65.48％.在白浆土中添加玉米秸秆培养后,其母质的固碳能力大于耕层土壤.%[Objective] The purpose of this study is to illustrate effects of incorporation of organic material on organic carbon of the heavy fraction and composition of soil aggregates in the soil in the hope that the work may be of some important significance to scientific evaluation of the effects of incorporation of crop straw into the soil on soil fertility and the environment.[Method] An in-lab experiment was carried out incubating for 120 days columns of albic soil with corn stalk incorporated into top soil and parent material at a varying rate,and then analyses done for accumulation of organic carbon of heavy fraction,composition of soil aggregates and distribution of organic carbon in various fractions of soil aggregates as affected by incorporation rate of corn stalk.[Result] It was found that content of the organic carbon of heavy fraction in both the top soil and parent material increased simultaneously with the increasing incorporation rate of corn stalk.The two soils did not differ much in increment of the content of the organic carbon of heavy fraction,showing a slight difference of being only 0.34 g kg-1.However,they varied sharply in increasing rate of organic carbon.In the top soil,organic carbon increased by 85.51％ only and in the parent material by 556.23％.It was also found that,the incorporation of stalk promoted transformation of small aggregates (＜ 0.25 mm) to large aggregates (＞ 0.25 mm) in the soil.When the amount of corn stalk added is too high,＞ 2 mm size aggregates no longer increase but decrease.When corn stalk was incorporated at a rate of 3％ and 2％,the fraction of large aggregates contributed the most to the content of organic carbon in the soil reaching up to 69.90％ and 65.48％,respectively.[Conclusion] In this study,the addition of stalk promoted accumulation of organic carbon of heavy fraction and formation of large-sized aggregates and increased organic carbon content in aggregates in various particle-size,adding the appropriate amount of corn stalk can increase the contribution rate of organic carbon in the large-sized aggregates fractions.Compared to the top soil,that in the parent material soil had organic carbon increased by a far more high rate.The effect of the addition of extraneous carbon increasing organic carbon content in aggregates of all particle sizes was more apparent.The soil in the parent material layer was much higher than the top soil in carbon sequestration capacity,in the case that the former almost contained nil of organic carbon.