基于质量和数量方法的不同粒径土壤团聚体水稳性评价

Evaluation of water stability of soil aggregates with different particle-sizes based on quality and quantity methods

【目的】研究湿筛后不同粒径土壤团聚体质量和数量分布特征以及水稳性,为土壤结构的改良提供科学依据。【方法】以黄土丘陵区不同撂荒年限(7,14和34年)的草地和坡耕地土壤(对照,CK)为研究对象,从质量和数量的角度探讨了不同恢复年限和不同粒径土壤团聚体湿筛后粒径分布特征,选取粒径大于0.25mm团聚体含量(R0.25)以及平均质量直径(MWD)2个指标评价不同粒径团聚体的水稳性。【结果】(1)随着植被恢复年限的延长,土壤中粒径>1mm的团聚体质量分数增加,粒径为0.25～1mm的团聚体质量分数增加不明显;团聚体数量与质量变化规律一致,但数量变化量随粒径减小而成倍的增加。(2)不同粒径土壤团聚体湿筛后,粒径<0.25mm微团聚体的质量分数最高;团聚体数量则表现为随粒径的减小而成倍增加。(3)当粒径为0.25～5mm时,随着粒径的增大,土壤团聚体的水稳性降低,其中粒径2～5mm团聚体的水稳性最差。(4)当粒径为0.25～5mm时,有机质含量随粒径的减小呈增加趋势,各粒径团聚体有机质含量与MWD减小比例呈负相关,与R0.25呈正相关。【结论】用数量方法评价团聚体分布特征的结果与用质量方法评价的结果存在差异,小粒径团聚体的水稳性更强。

【Objective】The particle-size distribution characteristics and water stability of soil aggregates with different particle-sizes after wet sieve were explored to provide basis for the improvement of soil structure.【Method】Grassland and slope farmland(control,CK)at different abandonment ages(7,14 and 34 years)in Loess Hilly Region were chosen to study the distribution characteristics of the different restoration years and different particle size aggregates after wet sieve.The water stability was evaluated based on macro aggregate content(R0.25)and mean weight diameter(MWD).【Result】(1)With the increase of vegetation restoration time,the mass fraction of>1 mm macro-aggregate increased while the mass fraction of 0.25-1 mm aggregate increased inconspicuously in soil.The change of the number of aggregates was consistent with the quality,but the amount of change increased multiply with the decrease of particle size.(2)Soil aggregates with different particle-sizes after wet sieve,the content of<0.25 mm micro-aggregate was the highest.The number of aggregates increased multiply with the decrease of particle-size.(3)In the range of 0.25-5 mm particle-size,the water stability of soil aggregates decreased with the increase of particle-size,and 2-5 mm aggregate had the worst water stability.(4)In the range of 0.25-5 mm,the organic matter content tended to increase with the decrease of particle size.There was negative correlation between the content of organic matter and MWD reduce rate,while the content of organic matter had positive correlation with R0.25.【Conclusion】The evaluation of distribution characteristic of soil aggregates with quantity was different from the quality.Soil aggregates with smaller size had stronger water stability.