ABSTRACT

A study was conducted to evaluate soil water dynamics in fairway turfs during daylight hours on three different dates during the 1993 and 1994 growing seasons. The objectives were to evaluate bihourly soil moisture depletion patterns under established annual bluegrass and Penncross creeping bentgrass fairway turfs and to compare bihourly moisture depletion during daylight hours to daily adjusted evapotranspiration (ET). Four soil depths (0-5, 5-10, 10-15 and 15-25 cm) were sampled under three irrigation regimes: i) apply 2.5 mm daily; ii) apply 25 mm upon the appearance of wilting stress; and iii) return the soil to field capacity daily based on soil moisture depletion as measured by TDR. Soil moisture depletion patterns significantly varied by species, soil depth, irrigation treatment and time of day. Moisture depletion patterns were also dependent on initial moisture content and evaporative demand. The greatest change in soil moisture content was from the 0-5 cm depth for the field capacity and 2.5 mm daily irrigation treatments between 0900 and 1300 h. Moisture depletion data as measured by TDR for the irrigation treatments were generally more conservative than the adjusted Penman estimate from a weather station on site. This suggests that potential water savings could result from soil moisture depletion-based turf irrigation scheduling. Agreement between moisture depletion and daily adjusted Penman estimates was poor.