Changes in Water Stability of Soil Aggregates in A Solar Greenhouse in Different Planted Years and Their Relationship to Iron Oxide

The distribution and stability of soil aggregates and its relation to iron oxide during different plantation years are studied in a solar greenhouse. Soil samples were obtained from a vetatable bed within a greenhouse in Xinmin (Liaoning, China). The composition, water stability and percentage of aggregate destruction, as well as variations in different forms of iron oxides were evaluated at 5 time points (0, 2, 5, 8 and 16 years). Soil from a dry land in an open field was also collected for comparison. The quantity and water stability of >0.25 mm soil aggregates from 2 and 5 years were lower than those in the soil from the open field. These parameters significantly increased after five years. The contents of non-free iron oxides decreased under greenhouse cultivation, resulting in reduced aggregate stability. Free iron oxides were positively associated with >2 mm aggregates. Complex iron oxides were positively correlated with 2–0.25 mm and 0.25–0.053 mm aggregates but negatively correlated with <0.053 mm aggregates.