Subsurface water retention technology does not increase greenhouse gas emissions from sandy soils under semi-arid conditions

Subsurface water retention technology (SWRT), a polyethylene membrane-based technology, is known to enhance water retention and potentially reduce nutrient leaching beyond the root zone, thus improving crop yields, but its effect on greenhouse gas (GHG) emissions remains unclear. This study therefore evaluated the impact of SWRT on soil carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) fluxes over two growing seasons (November 2021 to March 2022 and April to August 2022) using maize (Zea mays) as a test crop under rain-fed conditions. This study used six replicate farms in Makueni County, Kenya. In each farm, SWRT were manually installed in two plots, and the control was represented by a plot with no SWRT, with each plot measuring 20 by 10 m. Static chambers were installed, and GHG samples were collected bi-weekly to determine CH4, CO2, and N2O fluxes. SWRT plots emitted lower GHG during both growing seasons than the control plots. The mean daily emissions from SWRT plots ranged between -3.54 to -0.009 g CH4-C ha-1 day-1 , 1790 to 5790 g CO2-C ha-1 day-1 and -0.07 to 2.69 g N2O-N ha-1 day-1 for CH4, CO2 and N2O, respectively. For the control plots CH4, CO2 and N2O emissions ranged between -4.02 to -1.44 g CH4-C ha-1 day-1 , 1980 to 5880 g CO2-C ha-1 day-1 and -0.49 to 40.47 g N2O-N ha-1 day-1 , respectively. Significantly higher plant height, leaf area index (LAI) and aboveground biomass were recorded in SWRT than the control. In both seasons, the differences in N2O, CH4 and CO2 between SWRT and control were however non-significant. As SWRT improved maize growth parameters, it can be regarded as a climate-friendly option as it improves crop growth on sandy soils without increasing GHG emissions.