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

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.