DIVERSE - DIVerse crop residues Engender Resilience of Soil functions and Ecosystem services

这个项目将检验这样一种观点，即覆盖作物的绿肥混合物是增加进入土壤的碳化合物多样性的一种易于处理的手段，这种增加的生化多样性导致土壤微生物群落产生的酶的多样性增加，反过来，在洪水和干旱等干扰期间和之后，有可能为作物提供更多的营养。人们认识到，本世纪需要可持续地加强我们的粮食生产系统，以满足全球需求。由于次优的生长条件，通过遗传改良实现的作物产量潜力的增加并没有转化为相同幅度的农场产量增加。种植作物的土壤的次优质量和健康状况是实现遗传产量潜力的主要制约因素。由于不可持续的土壤管理降低了土壤微生物群落提供基础功能和服务（如养分矿化）的能力，作物未能实现产量。可持续土壤是指那些能够在受到干扰（如洪水和干旱）的情况下持续发挥生态功能，从而实现作物产量潜力的土壤，这些干扰预计会随着气候变化而变得更加频繁和严重。土壤微生物群落在农业土壤中实现这些功能所需的能量是由根部分泌物、作物残留物或有机肥料等形式进入土壤的有机化合物提供的。当一种单一的碳基质被添加到土壤中（例如，通过将前一种作物的残留物纳入耕地轮作中），最适应利用这种基质的微生物群落被激活。当使用几种生物化学对比的基质时，生态位的数量增加，能够利用这些生态位的生物群受到刺激。因此，增加了土壤微生物群落的功能多样性，并且提供生态系统功能（例如氮矿化）的能力更加安全，因为由于干扰（例如洪水或干旱）而抑制的一组生物可以由其他组来补偿，从而增强了土壤微生物群落对干扰的抵抗力和恢复力。覆盖作物的绿色肥料提供了一种易于处理的方法，将生物化学对比作物引入耕地作物轮作，因为它们的加入不会显著改变经济作物的农艺管理。由于每个植物科都产生独特的植物次生代谢物，因此可以通过纳入由不同植物科物种组成的覆盖作物混合物来进一步增加作物残留物的多样性。因此，多种覆盖作物混合物的掺入提供了生物化学上多样化的有机化合物，可以改变土壤微生物群落的结构，并增加能够代谢含氮有机化合物的生物的范围。土壤微生物群落的这种更大的多样性和功能冗余可能使与土壤有机质相关的氮矿化在洪水或干旱事件发生后，当植物需求恢复时得以维持。该项目将通过标记和确定土壤微生物群落的哪些成员将它们纳入其生物量，来跟踪作为一、二、三、四种不同覆盖作物残留物混合物施用于土壤的碳的命运。盆栽和田间试验将调查增加土壤中覆盖作物残留物的多样性是否会改变土壤微生物群落的结构，增加土壤在洪涝和干旱之前、期间和之后矿化氮的潜力，并增加有益生态系统服务的提供（作物产量和养分利用效率）。

This project will test the idea that cover crop green manure mixtures are a tractable means to increase the diversity of carbon compounds entering soils and that this increased biochemical diversity leads to a greater diversity of enzymes produced by the soil microbial community, and, in turn, the potential to make more nutrients available to crops during and after disturbances such as floods and droughts.There is a recognised need to sustainably intensify our food production systems this century to meet global demand. The increases in crop yield potential achieved by genetic improvements have not translated into on-farm yield increases of the same magnitude due to sub-optimal growing conditions. Sub-optimal quality and health of the soils on which crops are grown is a major constraint to the realisation of the genetic yield potential. Crops have failed to achieve their yield as a result of unsustainable soil management that has reduced the ability of the soil microbial community to deliver underpinning functions and services (e.g. nutrient mineralisation). Sustainable soils are those that can consistently achieve crop yield potential by delivering ecological functions despite disturbances (e.g. floods and drought) which are expected to become more frequent and severe as our climate changes. The energy required for the soil microbial community to deliver these functions in agricultural soils is provided by organic compounds entering the soil in the form of root exudates, crop residues or organic manures. When a single carbon substrate is added to a soil (e.g. by incorporating the residues of the previous crop in an arable rotation), a microbial community that is most adapted to exploiting that substrate is activated. When applying several biochemically contrasting substrates, the number of ecological niches increases and the groups of organisms capable of exploiting each of these niches are stimulated. The functional diversity of the soil microbial community is thus increased and the capability to deliver ecosystem functions (e.g. nitrogen mineralisation) is more secure since the suppression of one group of organisms due to a disturbance (e.g. a flood or a drought) can be compensated by other groups, thereby enhancing resistance and resilience of the soil microbial community to disturbance. Cover crop green manures offer a tractable means to introduce biochemically contrasting crop resides into arable crop rotations because their inclusion does not significantly change the agronomic management of the cash crop. Crop residue diversity can be increased further by incorporating cover crop mixtures comprised of species from a diverse range of plant families since each plant family produces unique plant secondary metabolites. Thus, the incorporation of diverse cover crop mixtures provides biochemically diverse organic compounds that may alter the structure of the soil microbial community and increase the range of organisms capable of metabolising nitrogen-containing organic compounds. This greater diversity and functional redundancy of the soil microbial community may enable the mineralisation of nitrogen associated with the soil organic matter to be maintained after a flood or drought event, when plant demand is restored. This project will track the fate of carbon applied to soils as unary, binary, tertiary and quaternary mixtures of contrasting cover crop residues using by labelling them and determining which members of the soil microbial community incorporate them into their biomass. Pot and field experiments will investigate whether increasing the diversity of cover crop residues incorporated into soils alters the structure of the soil microbial community, increases the potential for the soils to mineralise nitrogen, before, during and after flooding and drought, and increase the delivery of beneficial ecosystem services (crop yield and nutrient use efficiency).