Responses of soil organic carbon to conservation practices including climate-smart agriculture in tropical and subtropical regions: A meta-analysis

Considering the current threatening conditions of climate change, Climate Smart Agriculture (CSA) aims to improve the soil health and its organic carbon stocks by encouraging soil carbon sequestration through conservation practices in agricultural lands. However, the effects of these practices differ due to diverse climatic scenario, soil characteristics and management system. To identify the suitable practices that can be effective under tropical and subtropical conditions, a systematic evaluation in the form of a meta-analysis of these practices and their outcomes was performed over those regions. In this work we have included 516 observations from 84 articles published from 2000 to 2021 to analyse the influence of three CSA practices (conservation tillage, cover crop and biochar application) on the SOC (soil organic carbon) stocks over varying periods of experimentation. In addition to this, the combined effect of CSA and other conservation agronomic practices such as agroforestry has also been considered in the analysis. The results showed that biochar application had the most influence upon SOC stocks in the agricultural lands (25.38%) followed by conservation tillage (18.81%) and cover crop (15.8%). Medium term experiments (6-20 years) of these conservation practices showed about 31.00-96.15%improvement in SOC while the effects gradually diminished in long term experiments (>20 years). The combinations of these practices have been observed to have an evidently positive impact upon the SOC stocks in general. This work provides a systematic evaluation of all the widely performed CSA and other conservation practices and their effects on SOC dynamics under differing management settings.