Early effects of conservation agriculture on soil organic carbon dynamics of Mollisols in Cambodia

Abstract

Cambodia has faced drastic agrarian changes over the last twenty years with a rapid and massive transformation of the uplands from forest into arable land. Soil quality depletion is one of the main drivers of the resulting decline in crop productivity and increasing production costs in the uplands of Battambang province. The objective of the study was to assess the early effects of conventional plough‐based (20 cm) management (CT) and two conservation agriculture‐based (CA) cropping systems (the use of a single—CAS vs. multiple cover crop species—CAM) on a maize monocropping system using three soil organic carbon (SOC) fractions on Mollisols in Battambang province. SOC content, permanganate oxidizable carbon (POXC) and soil CO2 basal respiration through SituResp® were recorded at a depth of 0–10 cm. Twelve sampling periods were used over the growth period of the cover crops and during the maize cycle. POXC and SituResp® were highly sensitive to management practices with, across the 12 sampling periods, higher values (p < .05) under CA than CT, with an average increase of 6% and from 20% to 23%, respectively. No difference was observed in SOC content between the practices in our sampling periods. Seasonal variations were observed in both POXC and SituResp®. POXC underwent larger fluctuations following critical weather events than SituResp®. This study showed that POXC and SituResp® were rapidly sensitive to changes in agricultural management practices. POXC and SituResp® are largely influenced by seasonality and could help clarify the impact of weather patterns on soil C dynamics.

Diachronic assessment of soil organic C and N dynamics under long-term no-till cropping systems in the tropical upland of Cambodia

“…Diversified NT cropping systems enhance the SOC stock in the topsoil layer only after a several years of implementation (Hok et al, 2015) and pools (Sá et al, 2014;Briedis et al, 2018;Sithole et al, 2019;Cooper et al, 2021;Rodrigues et al, 2022), especially through an increase in physical protection of SOC inside soil aggregates (Six et al, 2002;Sithole et al, 2019;Rodrigues et al, 2022). In addition, numerous studies have reported the co-benefits of NT cropping systems on soil health enhancement (Pheap et al, 2019;Koun et al, 2023), increased water infiltration, reduced soil erosion (TerAvest et al, 2015;Sithole et al, 2019), and enhanced microbial activities (Hok et al, 2018) and abundance (Lienhard et al, 2013). Yet, there are still arguments about the benefits of CA and NT cropping systems and associated factors that determine SOC accumulation.…”

“…Cambodian soils are seriously threatened by inappropriate agricultural systems. The returns on taking actions against land degradation are estimated at 3 US dollars for every dollar invested in restoring cropping systems on soil health, and SOC sequestration have been reported in several studies (Hok et al, 2015(Hok et al, , 2018(Hok et al, , 2021Pheap et al, 2019;Suong et al, 2019;Sar, 2021;Koun et al, 2023), however, the information on the impact of long-term NT systems on the changes in SOC stock remains scarce in the country as well as in Southeast Asia. There is a need to document the long-term changes in SOC stocks under CA and NT cropping systems to fill in the knowledge gaps as well as provide robust evidences to land use planners and policymakers.…”