Effect of greenhouse soil management on soil aggregation and organic matter in northeast China

The effect of greenhouse soils on soil aggregation and soil organic carbon (SOC) cycling should be evaluated to maximize the benefits of solar greenhouses rationally. The relationship between aggregate stability and SOC fractions was investigated during a long-term greenhouse experiment for 16 years in Shenyang, China. Wet-sieving method was used to determine aggregate size distribution, water-stable aggregates, and mean weight diameter (MWD) as indices of soil aggregate stability. SOC fractions were also determined. The stability of macroaggregates decreased within 5 years of converting open vegetable fields to greenhouses, and a similar trend for MWD was observed. The stability of microaggregates also decreased. LF250 carbon in greenhouse soils was correlated with the amount of 2-0.25 mm size classes (r = 0.984**). As a result, a labile SOC existed in macroaggregates and was susceptible to loss. Positive correlations were also determined between water-stable microaggregates and intra-microaggregate particulate organic matter (r = 0.991**), between water-stable macroaggregates and intra-microaggregate particulate organic matter within macroaggregates (r = 0.998**), and between intra-microaggregate mineral-associated organic matter within macroaggregates (r = 0.971**). This result indicated that greenhouse soil management significantly affected the stability of aggregation and the cycle of soil organic matter. (C) 2015 Elsevier B.V. All rights reserved.