Do cover crops increasethe resilience and sustainability of the agri-food system?

世界上超过三分之一的土壤资源正在退化，影响了粮食生产。包括环境变化在内的其他未来威胁也将影响土壤系统提供包括粮食生产在内的各种生态系统服务的能力。我们有农业系统中可用的土壤管理工具来减少土壤退化，但鉴于这些未来的威胁，我们几乎不了解它们是否能提高土壤的恢复力。覆盖作物（在经济作物之间种植以提供环境效益的可耕地轮作作物）就是这样一种工具，它产生的生物质进入土壤并为土壤食物网提供养分。覆盖作物提供了一种易于处理的方法来增加可耕地景观的植物多样性，因为在不改变经济作物的农艺管理的情况下，可以同时种植不同种类的混种作物。覆盖作物复合栽培可以包括相互提供不同环境效益的植物，并包括来自产生不同植物次生代谢物的不同植物科的物种。然而，目前尚不清楚的是，进入共同根际和碎屑圈的生物量的生化多样性在多大程度上导致了土壤食物网结构的相互作用，从而形成了一个群落，该群落比多元文化中单个成员的总和更有能力提供土壤功能并确保对环境变化的恢复力。最重要的假设是，覆盖作物复合栽培中增加的植物多样性导致土壤食物网响应，使土壤对环境变化和短期扰动具有更大的恢复力。这一假设是合理的，因为当向土壤提供作物残留物和根系分泌物的单一来源时，最适合开发该资源的食物网将被激活，但当应用几种生物化学对比基质的混合物时，生态位的数量增加，能够竞争性地利用这些生态位的生物群被刺激。这一假设将通过在实验室尺度、田间地块尺度和景观尺度上进行实验来验证，目标如下：1。与各部分之和或对照相比，确定复合栽培是否改变了土壤食物网，提供了更大的土壤功能，并增加了经济作物产量。确定复合培养是否能使土壤微生物群落更具弹性。调查土壤类型对覆盖作物复合栽培效益的影响。田间地块规模：这个博士项目将利用并延长在索宁雷丁大学实验农场已经建立的田间实验的寿命。三叶草、荞麦、油萝卜和向日葵每年都在小块土地上种植，要么是单种单一栽培，要么是在秋季播种的谷类作物之间轮作第四季混养。每年测量土壤微生物、中系动物和大型动物群落的生物量、组成和活动及其与土壤结构、养分有效性和作物产量的关系，以实现目标1。实验室规模：开放式顶室将安装在上述现场实验的地块上，以模拟与预测的英国环境变化一致的冬季变暖和夏季热浪。将使用实验室呼吸计和最近量化土壤恢复力的方法定期分析室下方和邻近土壤的恢复力，以解决目标2。景观规模：将招募农民网络，在景观中建立不同土壤类型的田间试验。

Over a third of the World's soil resources are degraded, compromising food production. Additional future threats including environmental change will also affect the capability of soil systems to deliver a variety of ecosystem services, including food production. We have soil management tools available in agricultural systems to reduce soil degradation yet there is little understanding whether they can increase soil resilience in light of these future threats. Cover crops (crops grown between cash crops in an arable rotation to provide environmental benefits) are one such tool which generates biomass that enters the soil and feeds the soil food web. Cover crops offer a tractable means to increase the botanical diversity of arable landscapes because a polyculture of contrasting species can be simultaneously cropped without changing the agronomic management of the cash crop. Cover crop polycultures can comprise plants that provide different environmental benefits to one another and include species from different plant families that produce different plant secondary metabolites. However, it is unclear to what extent the resulting biochemical diversity of the biomass that enters the shared rhizpsphere and detritosphere of a polyculture results in interactions that shape the structure of the soil food web to form a community that is more capable of delivering soil functions and securing resilience against environmental change than the sum of the individual members of the polyculture. The overarching hypothesis is that increased plant diversity in cover crop polycultures results in a soil food web response that provides greater soil resilience to environmental change and short term perturbations. The hypothesis is justifiedbecause when providing a single source of crop residues and root exudates to a soil, a food webthat is most adapted to exploiting that resource will be activated, but when applying a mixture of several biochemically contrasting substrates, the number of ecological niches increases and groups of organisms capable of competitively exploiting each of these niches are stimulated. This hypothesis will be tested by conducting experiments at the laboratory scale, field-plot scale, and the landscape scale with the following objectives: 1.Identify whether polycultures alter soil food webs, provide greater soil functions, and increase cash crop yield, compared to the sum of the parts, or a control.2.Determine whether polycultures engineer more resilient soil microbial communities 3.Investigate the impact of soil type on the benefits provided by cover crop polyculturesField-plot scale: This PhD project will make use, and extend the lifetime, of an already established field experiment on the University of Reading experimental farm at Sonning. Berseem clover, Buckwheat, Oil radish and Sunflower are grown annually in plots either as single species monocultures or as a quaternary polyculture between autumn-sown cereal crops in rotation. Annual measurements of the biomass, composition and activity of the soil microbial, mesofauna, and macrofauna community and its relationship with soil structure, nutrient availability and crop yield will be made to address Objective 1.Laboratory scale: Open top chambers will be installed on the plots of the field experiment described above to simulate winter warming and summer heatwaves consistent with projected environmental change in the UK. The resilience of soil from underneath and adjacent to the chambers will be assayed periodically using a laboratory respirometer and a recent methodology to quantify soil resilience to address Objective 2. Landscape scale: A network of farmers will be recruited to establish field trials on contrasting soil types across a landscape.