The effects of land management patterns on soil carbon sequestration and C:N:P stoichiometry in sloping croplands in southern China

Excessive use of sloping soil in agriculture can result in loss of soil carbon (C) and stoichiometric imbalances, leading to soil degradation and a reduction in ecosystem services. Therefore, studying the effects of different utilization patterns on soil C stocks and stoichiometry is critical for the sustainable development of agriculture on uneven terrain. Here, we conducted a 7-year field study of cropland with a 10% slope, comparing soil C, nitrogen (N), and phosphorus (P) stocks and ratios between experimental plots of naturally abandoned land and different planting patterns (peanuts, daylily, oil tea planting with bare floor or inter-row coverage of straw, white clover or peanuts). We found that oil tea planting without inter-row coverage significantly lessened soil total C, microbial C and N, soil organic C, dissolved organic C, readily oxidizable C and available N compared with natural abandonment, whereas peanuts showed smaller differences, and daylily planting was most similar to natural abandonment. We also found that most planting patterns exacerbated soil C and P imbalance through the combination of C loss and P addition from fertilization. Our results show that inter-row coverage of straw or white clover can significantly alleviate these adverse influences. The atomic C:N and C:P ratios across all experimental plots were 5.10 ~ 30.5- and 0.675 ~ 8.13-fold lower, respectively, than the median values for Chinese soils, indicating that soil restoration or reasonable utilization has a high C sequestration potential, but it may be limited by P. These results suggest that perennial crops, such as oil tea with intercropping, can be nearly as effective as natural forest succession to reduce soil degradation on sloped farmland.