Soil salinity and land use-land cover interactions with soil carbon in a salt-affected irrigation canal command of Indo-Gangetic plain

Abstract

Soil salinity poses a threat to the sustainable management of agricultural landscapes and has an effect on soil carbon storage. This study investigated land use-land cover (LULC) relations with soil organic carbon (C) in a salinity-infested landscape with inter-spun vegetated and non-vegetated land area. A sodicity infested command area (~100 ha) along Sharda Sahayak canal in Uttar Pradesh, India was selected for studying LULC effects on soil organic carbon (C) and soil properties to 60 cm soil depth. The area was divided in a grid of 100 m × 100 m, and soils were sampled and analyzed at 140 geo-referenced points representing five LULC classes. The LULC dominant in the representative area were barren-coverless (BC), barren-grass cover (BG), rice-fallow (RF), rice-wheat (RW), and rice-okra-mentha (ROM). Soil organic C decreased with depth, decreased with increase in soil pH, and decreased with an increase in exchangeable sodium percentage (ESP). The effects were highly significant in surface layers (0–0.3 m). Similarly with electrical conductivity (EC) too, soil organic C had a negative correlation. Soil organic C varied significantly with LULC. The soil organic C content decreased in the order: ROM > RW > RF > BG > BC. As the intensity of crop/plant cover increased, the soil salinity (ESP, pH and EC) decreased. The average soil ESP was maximum in BC (44%) followed by BG (30%), RF (15%), RW (8.5%), and ROM (7.0%). The cumulative probability trends indicated the probability of lesser ESP with increased vegetative cover/primary productivity. A strong (p < 0.001), a negative relationship was observed between soil organic C and pH in rice-based systems. Analysis of soil organic C stock with depth for the studied LULCs indicated 4–70% (grass cover to rice-wheat cropping sequence) increase in total soil organic C stock just by supporting vegetative cover on barren sodic land. The study was indicative of scope for soil C sequestration and reclamative effects in salt-affected areas of Indo-Gangetic region by adopting appropriate land use strategies, which may include the adoption of rice-based and grass-based cropping systems, to check the development of sodicity in soils.