Approaches to scheduling water allocations to kikuyugrass grown on a water repellent soil in a drying-climate

Water allocation is a principal planning method for managing water supplies to agricultural and horticultural land in drying climates. Regulatory bodies often establish the water allocation amount, but its distribution during the irrigation season is left to the land manager's discretion. We evaluated approaches to best manage water allocations to a warm-season turfgrass [Pennisetum clandestinum (Holst. Ex Chiov)] grown on a free-draining sand prone to surface (0–25 mm) soil water repellence in a Mediterranean climate in south-western Australia under ‘deficit irrigation’, in a two-year field study. The three factorial experiment consisted of three levels for each treatment applied to plots (10 m²) of kikuyugrass: water allocation (5000, 6250 or 7500 kL ha⁻¹ yr⁻¹), irrigation schedule, and soil wetting agent rate (nil, recommended ‘label’ rate, double recommended ‘label’ rate), and was replicated three times. The irrigation schedules were based on historical net evaporation at the site, and then refined monthly using in-season net evaporation data or measurements of soil water content. Kikuyugrass growth and color was adequate when irrigated using the current regional water allocation (7500 kL ha⁻¹ yr⁻¹) under a low wear situation and to a lesser extent when the water allocation was lowered to 6250 kL ha⁻¹ yr⁻¹. Application of a soil wetting agent diminished water repellence and improved kikuyugrass color for 7500 or 6250 kL ha⁻¹ yr⁻¹ water allocations. Distributing a water allocation based on historical monthly net evaporation rates was a simple and effective scheduling approach to maintaining a warm-season turfgrass.