Uses of Hydrophobic Siloxane Polymer (Guilspare®) for Soil Water Management: Application in the Sultanate of Oman

The effectiveness of a non-toxic hydrophobic polymer (Guilspare ®) in irrigated agriculture to reduce soil water evaporation, improve water distribution, enhance salt leaching, and increase field water-use efficiency of crops was studied under laboratory and field conditions. Guilspare®, sprayed on soil as an aqueous solution, reacts with surface soil particles, which become hydrophobic. In a soil column experiment conducted under ambient summer conditions, application of the hydrophobic polymer substantially reduced cumulative evaporation relative to untreated columns. The pattern of water loss from Guilspare® treatments was approximately linear over time, while the pattern of water loss for controls was cyclic. The rates of water loss from control columns were significantly higher within 24 hours of water addition than treated columns. Guilspare® treatment substantially reduced the amount of water loss during the constant rate stage (Stage I) of soil drying. The rates of Stage I drying from control columns were higher than during the falling rate stage (Stage II) of soil drying. The patterns of water and salt distribution with depth were substantially different with moderately saline soil after 36 days of watering. Guilspare® application showed an increase in soil water contents at all soil depths of treated columns relative to controls. Guilspare® treated soil columns also showed increased salt content at lower soil depths than controls. In field trials, yields of Okra (Adelmoschus esculentus), transplanted in April and October 1998 from treated and untreated control plot, at three different rates of irrigation, were higher on treated plots. Treated plots, with 25 percent less water (April-planting) and 50 percent less water (October-planting), gave similar yields to untreated plots. The treatment had a marked effect on suppressing weed infestation of airborne weed seeds. A wider perspective of the potential uses of the polymer in semi-arid and arid countries is proposed including: geomembrane type applications to assist water management in cultivating soils of low water holding capacity; maintaining salt free conditions in the rooting zone of perched soil layers above saline horizons; reductions in water losses during conveyance; and run-off entrapment. This paper is offered as a contribution to stimulating interest in using a relatively new water conservation technology to help increase the water use efficiency of renewable and fossil water in Arabian Gulf Countries.