Ecol Appl. 2014 Apr;24(3):560-70. doi: 10.1890/13-0616.1.
Our increasing dependence on a small number of agricultural crops, such as corn, is leading to reductions in agricultural biodiversity. Reductions in the number of crops in rotation or the replacement of rotations by monocultures are responsible for this loss of biodiversity. The belowground implications of simplifying agricultural plant communities remain unresolved; however, agroecosystem sustainability will be severely compromised if reductions in biodiversity reduce soil C and N concentrations, alter microbial communities, and degrade soil ecosystem functions as reported in natural communities. We conducted a meta-analysis of 122 studies to examine crop rotation effects on total soil C and N concentrations, and the faster cycling microbial biomass C and N pools that play key roles in soil nutrient cycling and physical processes such as aggregate formation. We specifically examined how rotation crop type and management practices influence C and N dynamics in different climates and soil types. We found that adding one or more crops in rotation to a monoculture increased total soil C by 3.6% and total N by 5.3%, but when rotations included a cover crop (i.e., crops that are not harvested but produced to enrich the soil and capture inorganic N), total C increased by 8.5% and total N 12.8%. Rotations substantially increased the soil microbial biomass C (20.7%) and N (26.1%) pools, and these overwhelming effects on microbial biomass were not moderated by crop type or management practices. Crop rotations, especially those that include cover crops, sustain soil quality and productivity by enhancing soil C, N, and microbial biomass, making them a cornerstone for sustainable agroecosystems.
我们对玉米等少数几种农作物的依赖日益增加，这导致了农业生物多样性的减少。轮作中作物数量的减少或轮作被单一栽培所取代，是造成这种生物多样性丧失的原因。简化农业植物群落的地下影响仍未得到解决；然而，如果生物多样性的减少降低了土壤中的碳和氮浓度、改变了微生物群落，并像在自然群落中报告的那样破坏了土壤生态系统功能，那么农业生态系统的可持续性将受到严重影响。我们对 122 项研究进行了荟萃分析，以研究作物轮作对土壤总碳和总氮浓度的影响，以及在土壤养分循环和物理过程（如团聚体形成）中起关键作用的周转更快的微生物生物量碳和氮库。我们特别研究了轮作作物类型和管理实践如何影响不同气候和土壤类型中的碳和氮动态。我们发现，在单一栽培中添加一种或多种作物进行轮作，可使土壤总碳增加 3.6%，总氮增加 5.3%，但当轮作包括覆盖作物（即不收获但用于增加土壤肥力和捕获无机氮的作物）时，土壤总碳增加 8.5%，总氮增加 12.8%。轮作大大增加了土壤微生物生物量碳（20.7%）和氮（26.1%）库，而这些对微生物生物量的压倒性影响不受作物类型或管理实践的调节。作物轮作，特别是那些包括覆盖作物的轮作，通过提高土壤中的碳、氮和微生物生物量来维持土壤质量和生产力，使它们成为可持续农业生态系统的基石。
