Nitrogen Effects on Creeping Bentgrass Drought Tolerance.

Nitrogen is the most commonly limiting soil nutrient in agricultural situations. In this study we investigated the relationship between nitrogen levels and turfgrass drought tolerance. We hypothesized that low nitrogen level before drought could increase drought tolerance, as more root growth than shoot growth could be stimulated under carbon-limited conditions. Tyee creeping bentgrass was grown on sand in the 5 cm diameter PVC pipes in the green house. Four weeks of nitrogen fertilization was applied before drought at three levels: 0.1, 0.5, and 1.0 g N/m²/wk (Low, medium, and high N). Grass was then moved to growth chambers for drought treatments: well-watered, water withheld for 10 days then resume for 7 days (periodic drought), water withheld for 17 days (prolonged drought). All grass was then rewatered for 7 days (drought recover period). Photosynthesis rate, turf visual color, clipping weight, evapotranspiration, and soil water content was measured every other day during drought. Root at different depths and verdure were harvested at day 0, 10, 17, and 24 during drought. Root mass and length, and leaf relative water content were measure for each harvest. First year results show that increase N rate increase color and photosynthesis rate for all drought treatments, as well as increase root mass >12 cm depth. Medium N rate increase root mass at 3-12 cm depth. These one-year results suggest that higher N rate before drought increase turfgrass drought tolerance through increased color and photosynthesis rate.