Which cropland greenhouse gas mitigation options give the greatest benefits in different world regions? Climate and soil‐specific predictions from integrated empirical models

Abstract

Major sources of greenhouse gas (GHG) emissions from agricultural crop production are nitrous oxide (N2O) emissions resulting from the application of mineral and organic fertilizer, and carbon dioxide (CO2) emissions from soil carbon losses. Consequently, choice of fertilizer type, optimizing fertilizer application rates and timing, reducing microbial denitrification and improving soil carbon management are focus areas for mitigation. We have integrated separate models derived from global data on fertilizer‐induced soil N2O emissions, soil nitrification inhibitors, and the effects of tillage and soil inputs of soil C stocks into a single model to determine optimal mitigation options as a function of soil type, climate, and fertilization rates. After Monte Carlo sampling of input variables, we aggregated the outputs according to climate, soil and fertilizer factors to consider the benefits of several possible emissions mitigation strategies, and identified the most beneficial option for each factor class on a per‐hectare basis. The optimal mitigation for each soil‐climate‐region was then mapped to propose geographically specific optimal GHG mitigation strategies for crops with varying N requirements. The use of empirical models reduces the requirements for validation (as they are calibrated on globally or continentally observed phenomena). However, as they are relatively simple in structure, they may not be applicable for accurate site‐specific prediction of GHG emissions. The value of this modelling approach is for initial screening and ranking of potential agricultural mitigation options and to explore the potential impact of regional agricultural GHG abatement policies. Given the clear association between management practice and crop productivity, it is essential to incorporate characterization of the yield effect on a given crop before recommending any mitigation practice.

Simulating greenhouse gas mitigation potentials for Chinese Croplands using the DAYCENT ecosystem model

“…There have been many studies on best management practices (BMPs) to mitigate GHG emissions in agriculture, by increasing SOC stocks, and through direct reduction of CH 4 or N 2 O emissions from the croplands (Hillier et al, 2012;Paustian, 2012;Post et al, 2012). Conservation tillage has been considered a key practice to preserve SOC stocks in soils and slow carbon turnover through enhancement of aggregate stability in the soil (Six et al, 2004;Ogle et al, 2012;Paul et al, 2013).…”

“…Given that the effects of mitigation management practices vary with different environmental conditions (soil type, climate, cropping systems, etc.) (Hillier et al, 2012), it is necessary to assess the GHG mitigation potentials under various practices in different regions of China.…”

Conservation agriculture and ecosystem services: An overview

“…Fertility management may be the single most important factor to increase residue production and ultimately increase soil C storage, whether the system is NT or CT or incorporates crop rotations (Giller et al, 2009). This will be important for increasing C inputs and soil C in low input-low productivity systems found in much of Sub Saharan Africa and parts of South Asia (Paul et al, 2013;Thierfelder et al, 2013b;Dube et al, 2012;Ghimire et al, 2012;Hillier et al, 2012). As a rough comparison using average regional yields (Hazell and Wood, 2008) and a harvest index of 50% for maize, farms in the US generate 10 Mg ha −1 of maize residue while 3 and 1-2 Mg ha −1 are produced in South Asia and Sub Saharan Africa, respectively.…”

A comparison of carbon accounting tools for arable crops in the United Kingdom

“…The Cool Farm Tool utilises emission factors on specific soil parameters and on specific fertiliser types (Hillier et al 2011;Hillier et al 2012). The RSB calculations are based on Ecoinvent (Nemecek et al 2007) when following the RSB methodology, or the IPCC (Tier 2) when following the RED methodology (De Klein et al 2006).…”