Cropping system diversification careful selection of crop rotations to reduce

Cropping system diversification careful selection of

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GHG emissions [113]. Cropping system diversification, careful selection of crop rotations to reduce nutrient loss, and improved soil organic matter content are means by which to promote sustainable intensification. Yet, this often involves a set of complex trade-offs for producers and their livelihoods [114], emphasizing the need for a CSA strategy that involves stakeholders from the beginning to develop viable scenarios that include both mitigation and adaptation to climate change. The examples presented here demonstrate how strategies for N fertilization prac- tices provide both mitigation and adaptation benefits by decreasing GHG emissions, reducing reliance on synthetic mineral fertilizer and enhancing food security. Enhanced-efficiency fertilizers (EEFs), such as slow- release fertilizers or those containing nitrification inhibi- tors and urease inhibitors, hold potential to mitigate GHG emissions. According to the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report [114], the mean mitigation potential of N 2 O by nutrient management using nitrification inhibitors and slow-release fertilizers has been estimated to be 0.07 t Steenwerth et al. Agriculture & Food Security 2014, 3 :11 Page 8 of 39
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CO 2 -eq ha 1 yr 1 (as a reference, agriculture accounted for an estimated 5.1 to 6.1 GtCO 2 eq yr 1 in 2005, which amounts to 10% to 12% of total global anthropogenic emissions of GHGs). In practice, N 2 O emissions decreased by 54% from a no-till corn dry bean rotation receiving urea, urease and nitrification inhibitors in comparison to a urea-only application in Colorado (USA) [115]. According to a recent global meta-analysis of enhanced-efficiency fer- tilizers, nitrification inhibitors can reduce N 2 O emissions by 38% and polymer-coated fertilizers by 35%, on average, compared to conventional fertilizer, but urease inhibitors alone are not as effective in reducing N 2 O emissions [116]. Nitrification inhibitors are compatible with both chemical and organic fertilizers, making them a seemingly attractive mitigation option, but their efficacy varies with edaphic factors. For example, EEF materials were applied to rainfed corn in the central Corn Belt (Midwest region, USA), a more humid region than Colorado [117]. Al- though all EEF treatments had lower cumulative emissions than the treatment that did not include EEFs, episodic N 2 O emissions from EEF treatments corresponded to rainfall patterns, and the relative effectiveness among EEF materials was similar. Together, these findings suggest that the impact of EEF materials may be diminished in rainfed agriculture systems compared to irrigated systems with regulated water availability. Although yield responses to EEF materials may also vary with respect to crops and location, consistent yield increases in corn (central Corn Belt) grown with EEF materials were reported to occur as a result of the increased duration of photosyn- thetic leaf area during grain-filling [118]. In microirrigation
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