Can conjunctive use of gypsum, city waste composts and marginal quality water rehabilitate saline-sodic soils?

Abstract

Soil sodicity is major stress limiting crop production in the arid and semi-arid regions where groundwater contains excess salts with variable sodium adsorption ratio (SAR). This study investigated the impact of farmyard manure (F) and city compost in conjunction with gypsum to rehabilitate saline-sodic soil having pH1:2 (10.7), electrical conductivity (EC1:2; 3.09 dS m−1) and exchangeable sodium (70.3 %). Soil amended with gypsum (25 and 50 % of gypsum requirement, GR) and/or with 10 t ha−1 F (GR25 F), Karnal (GR25 K) and Delhi compost (GR25D) were incubated at moisture ∼60 % maximum WHC. One month incubated soils were sequentially leached up to ten pore volumes using saline water of SAR 5 and 15 with constant EC (6 dS m−1). The increment in SAR of applied water reduced the cumulative loss of Ca2+, Mg2+, and K+ and increased the release of Na+. Application of amendments and intense leaching decreased the soil pHs, ECe and alkalinity. Leaching with SAR 5 water decreased SAR of soil saturation extract to 9.7 compared with SAR 15 (17.2). Gapon’s selectivity coefficient (KG) pointed to the greater (0.017) adsorption preference of Ca2+ and Mg2+ in the soil leached with SAR 15 than SAR 5 (0.014) water. Reclamation depends on inherent soil ESP and supply of Ca2+ for exchange phase; KGbecomes more prioritized when SAR 15 water applied for leaching. Therefore, conjunctive use of gypsum (GR25) with compost is as effective as gypsum (GR50) on decrement of soil pHs and leaching of soluble salts.