Soil Water, Plant Yield and Root Dynamics under Application of Super Absorbent Polymers (SAP) in Semi-Arid Alfisols

The Semi-arid alfisols are predominant in rainfed agriculture having very low water holding capacity and surface crusting necessitating the adoption of water conservation technologies for drought management. Laboratory experiments were conducted in loamy sand for physical characterization of super absorbent polymers. Four polymer products (P1, P2, P3 and P4) of the commercial value with different concentrations (0.25%, 0.75%, 1.25% and 1.75%) were used and compared with control (soil without polymer). Among four polymer products tested, SAP P3 showed maximum water absorption of 312 g g⁻¹. Maximum soil moisture content of 42% and minimum of 20% was observed at field capacity (0.3 bar) and permanent wilting point (15 bar) with 1.75% SAP concentration. The experiment on water productivity with tomato was carried out with P3 having maximum water absorption at 50 and 80% moisture depletion levels and 0.25, 0.5 and 0.75% polymer concentrations in growth chambers. Significant difference (p=0.05) was observed among different polymer concentrations at 50% soil moisture depletion level. The maximum yield in tomato (2.71 kg/plant), water productivity (318.52 kg m⁻³), water saving (69.3%) and 90% enhanced root growth were obtained with 0.75% polymer concentration (P3) at 50% soil moisture depletion.