Distribution of organic matter in aggregates of eroded Ultisols, Central China
2010
Huang, Li | Wang, Chun Yan | Tan, Wen Feng | Hu, Hong Qing | Cai, Chong Fa | Wang, Ming Kuang
The relationship between organic matter contents and soil aggregates of particle size ranging from >4, 2-4, 1-2, 0.5-1 to 0.25-0.5mm in three eroded (slightly, moderately and severely) Ultisols in central China was investigated using dry-sieving and wet-sieving methods, as well as chemical analyses. In different eroded Ultisols, the size distribution percentages of >4 and 2-4mm macroaggregates obtained by dry-sieving method were all higher than that by wet-sieving method by separately between 12.3 and 45.7%, 3.0 and 24.7%, but the percentages of 0.25-0.5, 0.5-1 and 1-2mm macroaggregates showed opposite trend. Microaggregates (<0.25mm) averagely constituted the 30.1, 39.7 and 58.2% of aggregates after wet sieving in slightly, moderately and severely eroded soils, respectively. As the degree of erosion increased, the average content of >0.25mm water-stable aggregates (WSA) and average of mean weight diameter (MWD) decreased from slightly eroded soil to severely eroded soil by 28.0% and 0.14mm, respectively. The organic matter (OM) content of macroaggregate fractions from slightly and moderately eroded Ultisols rose with increasing in particle size fractions from 0.25-0.5 to >4mm, but that of macroaggregates fractions from severely eroded Ultisols decreased with increasing in particle sizes. The percentages of >0.25mm WSA correlated well with the OM contents of eroded Ultisols (r ² =0.6573, n =19). The OM contents of macroaggregates in eroded soils showed high correlation with that of the bulk soil, and the correlation coefficients decreased in the order of slightly>moderately>severely eroded Ultisols.
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