Research on soil particle size distribution and its relationship with soil organic carbon under the effects of tillage in the Heihe oasis
黑河绿洲区耕作影响下的土壤粒径分布及其与有机碳的关系

Effects of tillage on soil particle size distribution and its relationship with total organic carbon(TOC),active organic carbon(AOC),and nonactive organic carbon(NOC) are analyzed in the central Heihe Valley.Results show tillage significantly alters the percentage of particle sizes of 10-50 μm,50-250 μm,and 250-1000 μm while the uncultivated plots(sierozems,grey cinnamon soil,chestnut soil) are changed to the cultivated plots(alluvial soil and irrigated desert soil),respectively.And the percentage of soil particle size presents a thinning trend while aeolian sandy soil is changed to alluvial soil and irrigated desert soil.These changes also affect the relationship between soil particle size and soil organic carbon.Statistical results between soil particle size and soil organic carbon(TOC,AOC and NOC) show the similarities and differences at the cultivated and uncultivated plots.The similarity has a significantly positive(P<0.01 or P<0.05) correlation with soil silt-and clay-size fractions under 50 μm size and a significantly negative relation(P<0.01 or P<0.05) with sand fractions over 50 μm size.The difference is that there is significant relationship between soil organic carbon and particle sizes of 5-10 μm,10-50 μm,50-250 μm at the cultivated plots and particle sizes of <1 μm,1-5 μm,5-10 μm,10-50 μm,50-250 μm,and 250-1000 μm at the uncultivated plots.It is found that tillage increased AOC content and became the intrinsic reason of relationship change between soil organic carbon and particle size.