The PURR‐WICK system, as developed at Purdue University in 1966, provides an impermeable underlay, plus possible retention of free water by outflow drainage control. What would be the effect in this system of sand texture, depth of water reserve, and temperature? ‘Penncross’ bentgrass (Agrostis palustris Huds.) was grown in columns of finer and coarser sand mixes with water tables maintained at depths of 11, 25, and 40 cm in constant temperature chambers of 15 and 30 C for 9 weeks. Temperature had the greatest effect. At 15 C root growth was slow initially but steadily maintained. At 30 C initial root growth was rapid but declined to little or no growth, so that total root length at 15 C was three times that for 30 C. Within each temperature the water table ✕ sand interaction was significant. Root growth was better in the coarser sand for the 11‐ and 25‐cm water tables and better in the finer sand for the 40‐cm treatment. The deepest root growth was found at 15 C in the finer sand mix with the water table at 40 cm. Where oxygen diffusion was favored by coarse texture, roots were still limited by higher temperature.

Recent developments in plastic barrier placement under compacted sand for regulated availability and retention of water (PURR‐WICK Rootzone) raises questions of duration of availability. Creeping bentgrass (Agrostis palustris Huds) was studied under putting green conditions when grown on replicated 1‐m2 plastic‐lined plots containing dune sand, mortar sand, calcined clay, diatomaceous earth, and peat. Soil was not included in any of the rootzone mixtures because of its inherent structural instability. In 1968 and 1969, some infiltration rates exceeded 150 cm/hr and all were greater than 7 cm/hr, therefore, water movement was considered ample. The relative ability of the material in plots to retain moisture was measured by allowing the plots to dry‐down for 15 days between rains during August 1968 and for 17 days during July 1969. No irrigation was added to any plot until turf showed severe wilt. Bentgrass on plots containing the finer fractions of the dune sand, diatomaceous earth, various mixtures of sand, calcined aggregates, and peat did not require water for either period. Comparison of the dune sand treatments with and without subsurface irrigation showed that a constant moisture level could be maintained in the subirrigated plots. Depth ranged from 20 to 50 cm with 40 cm proving ample.