Sustainable Management of Agricultural Soils: Reducing Greenhouse Gas Emission and Enhancing Natural Fertility

土壤是生命的基础，很容易受到储存碳(C)和生产力的损失，特别是在集约化农业下。1例如，农业已经损失了1330亿吨土壤碳，仅此一项就占到了人为排放到空气中的二氧化碳总量的10-20%。1其中，土壤碳的损失降低了肥力，因此为了维持生产力，增加了包括氮(N)在内的合成肥料的应用。化肥的使用导致了产量的增加；2然而，与此同时，过度施肥也与环境质量恶化和温室气体(GHG)的排放有关，特别是一氧化二氮，一氧化二氮导致全球变暖的效力是CO23、4、5的300倍。因此，迫切需要确定有助于维持土壤肥力和生产力、同时减少温室气体排放的土壤管理做法。6英国的耕地农业与全球一样，面临着严重的土壤枯竭挑战，目前有一种改善土壤健康以确保粮食安全的动力。一种方法是在农业中引入轮作，以便在保持收入的同时，优化Leys(作为耕作之间的土壤休眠阶段)来提高肥力。英国一个新的多机构项目“通过在耕地轮作中整合牧草和绵羊放牧来恢复土壤健康”现在正在建立农场规模的试验田(2019-2022年)，以分别评估富含草和药草的牧草轮作和不放牧和耕作轮作对更广泛的农业环境有效性(图1)。据推测，带有固氮植物的草本植物将提高土壤肥力，从而减少在随后的种植中对肥料的依赖，为此，该项目的重点是测量土壤养分和生产力。由于计划轮作将通过其对土壤N和C转化过程的影响来影响温室气体的排放，因此，拟议的PHD研究将评估传统轮作(草-三叶草)和草本轮作对生物固氮、N矿化和温室气体排放的影响，以确定有效的土壤管理策略，以便纳入农业实践。

Soil is fundamental to life and is vulnerable to losses in stored carbon (C) and productivity, particularly under intensive agriculture.1 For example, 133 billion tons of soil C has been lost due to agriculture, which alone represents between 10-20% of the total anthropogenic CO2 emission into air.1 Among others, loss in soil C reduces fertility and thus to sustain productivity, application of synthetic fertilizers including nitrogen (N) has intensified. The use of fertilizers has led to increases in production;2 however, at the same time excessive fertilization has been linked to deterioration of environmental quality, and emission of greenhouse gases (GHG) particularly nitrous oxide, which is 300 times more potent in inducing global warming than CO23, 4, 5. Thus there is an urgent need for the identification of soil management practices that can help sustain soil fertility and productivity whilst reducing GHG emissions.6 Arable agriculture in the UK like the global seriously suffers from the soil exhaustion challenge, and there is a current impetus on improving soil health to ensure food security.One way is to introduce rotations in agriculture such that leys (as soil's resting phase in between cultivation) can be optimized for enhancing fertility whilst sustaining income. A new multi-institutional project in the UK on 'Restoring Soil Health through Integration of Leys and Sheep Grazing in Arable Rotations' is now establishing farm-scale experimental fields (2019-2022) to evaluate the broader agro-environmental effectiveness of rotations with grass and herb rich leys with and without grazing and tillage, respectively (Fig1). It is hypothesized that herbaceous leys with N fixing plants will enhance soil fertility that will reduce reliance on fertilizers in subsequent cultivations and to this effect the project is focused on measuring soil nutrients and productivity. Since the planned rotations will affect the emission of GHG through its impact on soil N and C transformation processes, which is not included in the consortium project, therefore, the proposed PhD research will evaluate the impacts of traditional (grass-clover) and herbal leys rotations on biological N fixation, N mineralization and greenhouse gas emission rates to identify efficient soil management strategies for incorporation into agricultural practices.