No-tillage lessens soil CO<sub>2</sub> emissions the most under arid and sandy soil conditions: results from a meta-analysis

Abstract

Abstract. The management of agroecosystems plays a crucial role in the global carbon cycle with soil tillage leading to known organic carbon redistributions within soils and changes in soil CO2 emissions. Yet, discrepancies exist on the impact of tillage on soil CO2 emissions and on the main soil and environmental controls. A meta-analysis was conducted using 46 peer-reviewed publications totaling 174 paired observations comparing CO2 emissions over entire seasons or years from tilled and untilled soils across different climates, crop types and soil conditions with the objective of quantifying tillage impact on CO2 emissions and assessing the main controls. On average, tilled soils emitted 21 % more CO2 than untilled soils, which corresponded to a significant difference at P < 0.05. The difference increased to 29 % in sandy soils from arid climates with low soil organic carbon content (SOCC < 1 %) and low soil moisture, but tillage had no impact on CO2 fluxes in clayey soils with high background SOCC (> 3 %). Finally, nitrogen fertilization and crop residue management had little effect on the CO2 responses of soils to no-tillage. These results suggest no-tillage is an effective mitigation measure of carbon dioxide losses from dry land soils. They emphasize the importance of including information on soil factors such as texture, aggregate stability and organic carbon content in global models of the carbon cycle.

Conservation Agriculture practices reduce the global warming potential of rainfed low N input semi-arid agriculture

“…NT) should be recommended in semi-arid areas. Supporting our findings, the recent meta-analysis of Abdalla et al (2015) pointed out that the abatement of C02-eq emissions through NT adoption is significantly higher in arid climates with low SOC content, as opposed to CT. Nitrous oxide (N2O) emissions have shown to carry less weight in GWP estimates than in previous studies (Mosier et al, 2006;Adviento-Borbe et al, 2007), but uncertainties associated with SOC accumulation and its calculation (Guardia et al, 2016) and the large climatic variability in rainfed semi-arid cropping areas, suggest that strategies that mitigate C0 2 -eq from other GWP components (N 2 0 losses and inputs, e.g. by adjusting N rates) must be also considered.…”

“…As reported by previous studies (e.g. Aguilera et al, 2013aAguilera et al, , 2015Plaza-Bonilla et al, 2015;Abdalla et al, 2015), NT significantly increased the SOC content compared with CT (Table 3). This occurred despite the higher SOC content in the 15-30 cm layer in CT (as opposed to NT/MT), as suggested by Baker et al (2007).…”

Greenhouse gas emissions in conservation and conventional agriculture systems under rainfed mediterranean agro-ecosystem

“…This finding was in agreement with Guardia et al (2016a) and Aguilera et al (2015). Results from a recent meta-analysis (Abdalla et al, 2015) concluded that NT system significantly reduced CO 2 -eq emissions and increased soil C stock particularly under arid and sandy soil conditions with low SOC content, supporting our findings. In spite of low weight of N 2 O emissions in net-GWP and the uncertainties associated to the calculation of C sequestration (Guardia et al 2016a), long-term NT system can be considered as a good strategy to mitigate CO 2 -eq emissions and increase the generally low SOC content of Mediterranean soils compared to MT and CT systems in rainfed semiarid agro-ecosystems.…”

How does tillage intensity affect soil organic carbon? A systematic review

“…Those soil types have, on average, a clay content of about 30 and 45%, respectively, which may help to slowdown SOC decomposition compared to coarser soils [58,59]. This is related to the fact that clay particles can help to stabilise decomposing litter by mineral associated bonds [1,2] and the aggregation is stronger, also promoting physical inaccessibility of SOC to the microbial community [3].…”