Soil Genesis, Survey and Classification Division, CSIR-Soil Research Institute, Kumasi, Ghana.
Department of Soil Resources Management, CSIR-College of Science and Technology, Kumasi, Ghana.
PLoS One. 2023 Aug 30;18(8):e0290687. doi: 10.1371/journal.pone.0290687. eCollection 2023.
Soil and microbial biomass carbon (C), nitrogen (N), and phosphorus (P) play an important role in soil nutrient dynamics in biogeochemical cycles of terrestrial ecosystems. However, increased human activities as a result of agricultural intensification on soil nutrients and microbial C:N:P stoichiometry are poorly understood in this fragile forest-savanna transition agroecosystem. This study aimed to (i) assess soil and microbial C, N, and P stoichiometry in different land use systems, and (ii) examine the effect of soil and microbial C, N, and P stoichiometry on soils susceptible to human-induced land use changes. A total of 82 composite soil samples at a depth of 0-20 cm were sampled from forest, savanna, grassland, fallow and cropland for laboratory analysis. The results revealed that the concentrations of C, N, and P were low in Fallow and Cropland compared to other land use systems. Analysis of variance in microbial C, N, and P stoichiometric ratios revealed a significant decreasing tendency compared to soil C:N, C:P and N:P ratios with no statistical significance (p < 0.05). The C:P and N:P ratios were low compared to the C:N ratio in land uses. A significant positive correlation was observed between MBC and MBN (0.95; p < 0.01), and with C and N (0.69; p < 0.01). There were significant interactive effects of land use on soil and microbial variables. The estimated microbial C:N:P stoichiometric ratios (21:2:1) were well constrained in the study area. The transition from Forest to Cropland resulted in 64%, 52%, and 71% reduction in C, N, and P, respectively. This implies that phosphorus is the main factor limiting productivity. The low availability of phosphorus in these tropical soils may have resulted in low C:P and N:P ratios. Therefore, we conclude that our results highlight the importance of phosphorus limitation on ratios of microbial C:P and N:P in landuse systems. Nutrient inputs such as fertilizers, manure and crop residues should be applied to croplands to improve soil and microbial C, N and P levels. Further, effects of land use on soil nutrient status and stoichiometry at 1-meter depth will be considered in our future work.
土壤和微生物生物量碳（C）、氮（N）和磷（P）在陆地生态系统的生物地球化学循环中对土壤养分动态起着重要作用。然而，在这个脆弱的森林-稀树草原过渡农业生态系统中，人们对农业集约化对土壤养分和微生物 C:N:P 化学计量的影响知之甚少。本研究旨在：（i）评估不同土地利用系统中的土壤和微生物 C、N 和 P 化学计量；（ii）研究土壤和微生物 C、N 和 P 化学计量对易受人类土地利用变化影响的土壤的影响。共采集了 82 个复合土壤样本，深度为 0-20 厘米，分别来自森林、稀树草原、草原、休耕和耕地，用于实验室分析。结果表明，与其他土地利用系统相比，休耕和耕地的 C、N 和 P 浓度较低。与土壤 C:N、C:P 和 N:P 比值相比，微生物 C、N 和 P 化学计量比的方差分析显示出显著的下降趋势，但无统计学意义（p<0.05）。与土地利用相比，C:P 和 N:P 比值较低。MBC 和 MBN 之间存在显著的正相关（0.95；p<0.01），与 C 和 N 之间也存在显著的正相关（0.69；p<0.01）。土地利用对土壤和微生物变量有显著的交互作用。在研究区域内，估计的微生物 C:N:P 化学计量比（21:2:1）得到了很好的约束。从森林到耕地的转变分别导致 C、N 和 P 的减少 64%、52%和 71%。这意味着磷是限制生产力的主要因素。这些热带土壤中磷的低有效性可能导致 C:P 和 N:P 比值较低。因此，我们得出结论，我们的研究结果强调了磷限制对土地利用系统中微生物 C:P 和 N:P 比值的重要性。应向耕地施入肥料、粪肥和作物残体等养分，以提高土壤和微生物 C、N 和 P 水平。此外，我们将在未来的工作中考虑土地利用对土壤养分状况和 1 米深度化学计量的影响。
