No abstract

No abstract

Maintaining high visual quality of turfgrass requires intensive management. Nitrogen fertilizer inputs in golf‐course turfgrass have raised some concerns regarding potential nitrate leaching into groundwater. This study investigated nitrate leaching from an overseeded bermudagrass (Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy) managed as a golf course fairway (mowing height in 1.3 cm). The study was conducted from 1994 to 1997, with two soil types (sandy loam and loamy sand), two irrigation regimes, and two N fertilization programs representing the typical resort‐turfgrass management practices in the semiarid southern California. Leachate was collected and its volume was measured from lysimeter assemblies each consisting of five metal cylinders. Results showed that the nitrate concentration and mass of the leachate from the loamy sand was lower than that from the sandy loam soil. The difference was attributed to N immobilization and clipping removal. The volume of leachate was greater in the loamy sand than in the sandy loam due to the higher water holding capacity of the latter. Average nitrate concentration of the leachate was lower than that of the irrigation water in five out of the six seasons, implying that if turfgrass is properly managed, it may provide an opportunity to mitigate nitrate loading to surface and ground waters, even when N application rate is high.

Putting greens usually receive high inputs of fertilizers and pesticides to meet the high demand for visual quality and to overcome the stress from close mowing and traffic. In this study, two commonly used fungicides, metalaxyl (methyl N-(methoxyacetyl)-N-(2,6-xylyl)-DL-alaninate) and chlorothalonil (2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile), were evaluated for their partitioning and persistence in a bentgrass (Agrostis palustris Huds) putting green under southern California climatic conditions. The putting green site was constructed according to the US Golf Association (USGA) specifications. Lysimeter assemblies installed at the center of each plot were used to monitor the leachate, flux chambers were used to measure volatilization, clippings were collected to determine the residues on grass, and soil cores were sampled to determine residues in the soil profile. Results showed that cumulative volatilization loss accounted for 0.10 and 0.02%, clipping removal 0.11 and 0.13%, and cumulative leaching 0.71 and 0.002% of the applied metalaxyl and chlorothalonil, respectively. The two fungicides were mainly found in the top 10 cm of the soil profile due to the high organic carbon content in the thatch and mat layers. The dissipation half-life was 1.4 days for metalaxyl and 4.9 days for chlorothalonil on grass, shorter than those found in agricultural fields. This study showed that, under normal turf management practices, the offsite transport of the parent fungicides was minimal. Future research should focus on investigating the fate and mobility of the metabolites of the fungicides.

I. Hypothesis, Experimental Procedures, and Cropping ResultsAn irrigation/cropping management strategy has been developed to facilitate the use of brackish waters for irrigation, with the goal of expanding the available water supply and minimizing the otT-site pollution potential of drainage disposal. A field experiment conducted in the Imperial Valley of California to test the strategy has produced four years of cropping results. After seedling establishment, when the crops were in a sufficiently mature, salt-tolerant growth stage, brackish drainage water (Alamo River) was substituted for the normal water (Colorado River) to irrigate wheat and sugarbeets (in a succes- Continued inside back cover