Granular wetting agents ameliorate water repellency in turfgrass of contrasting soil organic matter content

The effectiveness of four granular wetting agents to decrease water repellency in sandy soils of contrasting organic matter (OM) content and influences on kikuyugrass [Pennisetum clandestinum (Holst. Ex Chiov)] grown as turfgrass, were evaluated. A laboratory test assessed the wettability of two non-wetting soils (low OM, 4.7%; high OM, 17%) after treatment with granular soil wetting agents, with four being selected for field experimentation. A field experiment included two turfgrass ages (established from 20 week or 20 year old turfgrass in 2005; the latter included a 50 mm 'mat' layer and thus had high OM content in the surface soil), four granular soil wetting agents (plus a 'nil' as control), and five replicates. Surface soil (0-25 mm) water repellency, measured using the molarity of ethanol droplet test (MED), ranged from 0.4 M to 4.3 M during the irrigation season, and repellency was more severe in the soil with high OM (32%) content than low OM (8.6%) content. Soil wetting agents decreased the development of soil water repellency to varying extents, and maintained turfgrass quality; with improvement related to the amount of active ingredient applied. We recommend utilising an effective soil wetting agent, in combination with practices that limit the accumulation of soil OM, to decrease the severity and incidence of soil water repellency in turfgrass grown on sandy soils.