Effects of Earthworms on Soil Aggregates Formation,Stability and Soil Organic Carbon Distribution

A 30-days experiment was conducted to investigate the effects of earthworm activity on soil aggregates distribution,stability and soil organic carbon under different plant debris input in different soils.A soil(silt loam) with low-clay content and a soil(silt clay loam) with higher-clay content were chosen to be tested,all soils were sieved 0.25 mm to destroy all macro-aggregates.The debris used for test was maize straw with high carbon to nitrogen ratio and white clover residue with low carbon to nitrogen ratio.The earthworm Metaphire guillelmi was chosen for test.The results indicated that earthworm affect water-stable aggregates distribution,micro-aggregate dispersion and soil organic carbon distribution differently under different soil and plant debris input.Earthworm decreased the clay dispersion significantly(P0.05) and had no effect on the distribution of water-stable aggregates and mean weight diameter(MWD),and increased the distribution of soil organic carbon in silt plus clay under two kinds of plant debris input in silt loam soil.Meanwhile,earthworm decreased the dispersion of clay and clay plus clay significantly(P0.05) and formed 2 mm macro-aggregate,and increased the percentage of 2～0.25 mm macro-aggregate and MWD significantly(P0.05),and increased the distribution of soil organic carbon in 2 mm and 2～0.25 mm macro-aggregate significantly(P0.05) under two kinds of plant debris input in silt clay loam soil.The combinations of earthworm inoculation and plant debris input all increased soil organic carbon content significantly(P0.05) in the two soils.Earthworm inoculation was helpful for the recovery of soil structure and the increment of soil organic carbon under plant debris input in these regions where soil erosion and soil structure degradation are serious.