Abstract:
Anthropogenic climate change has caused increased soil salinity in South
Asia due to saltwater intrusion caused by sea level rise, input of fertilizers
with high salt index, and irrigation malpractices, etc. Salinity has a
multitude of impacts on plant and soil processes, leading to alterations
in gas fluxes and rice productivity. The remedial measures adopted on
salt-affected soils to reduce the salinity effect could enhance future
climate change if they cause an increase in greenhouse gas (GHG) emissions.
This study was conducted to find the best agricultural management
practices (BMPs) for salt-affected soils in rice cropping systems (i.e. the
major cropping system in Asia) in four South Asian countries (Sri Lanka,
India, Bangladesh and Pakistan) considering net GHG emissions and
other socioeconomic benefits associated with the adopted measures. The
salinity-affected sites were selected based on available information (e.g.
agricultural statistics and maps). Site-level measurements on soil parameters
and GHG emissions were made in control- and managed plots and
farmer surveys were conducted. Although organic amendments ameliorated
salinity, it could cause a net increase in carbon dioxide or methane
emissions depending on the soil conditions, particularly during the initial
stages. This impact could be ameliorated by combining organic amendments
with other management practices. In the Indo-Gangetic region,
poor soil drainage causing anaerobic conditions favoured nitrous oxide
emission under low to medium salinity. Yield losses and emissions in high
salinity sites were controlled through organic amendment, irrigation and
rice-fallow cropping sequence. The combination of transplanting of rice
seedlings, the addition of organic matter, and intermittent irrigated water
levels was identified as the BMP for Sri Lankan farmers. The outcome of
this project will be used to raise awareness among farmers and policymakers.
