In California, residential lawn area is second in planted acreage to production agriculture. Due to the demand for visually attractive lawns, relatively large amounts of N are often applied. The objective of this research was to investigate the effect of N source and application rate on tall fescue [Schedonorus phoenix (Scop.) Holub] visual quality and color, clipping yield, N uptake, and nitrate leaching under normal irrigation practices. Three annual N application rates (195, 293, and 390 kg ha−1) and four N sources (AN, ammonium nitrate; MUN, methylene urea; NON, natural‐organic nitrogen; and PCN, polymer‐coated nitrogen) were applied in four equal applications per year. The factorial experiment was replicated four times and conducted on a Hanford fine sandy loam at the University of California, Riverside's Turfgrass Research Facility from October 2002 to October 2004. Turfgrass visual quality and color ratings were evaluated every 2 wk. Clipping yield, clipping tissue total Kjeldahl nitrogen (TKN), and N uptake were measured or calculated in four 4‐wk growth periods per year. Suction lysimeters were used to collect soil water below the rootzone (leachate) to determine nitrate and ammonium concentrations once every two weeks. Soil nitrate and ammonium concentrations were analyzed at 12 and 24 mo. after initial fertilizer treatments. An annual N application rate of 195 kg ha−1 produced an acceptable to good quality tall fescue lawn. Higher rates were not necessary, and increased nitrate leaching. Among the N sources, slow‐release N resulted in less nitrate leaching than the fast‐release N source.

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.

Summer decline of annual bluegrass (Poa annua L.) putting greens is a major concern of golf course superintendents. Low soil water infiltration rates and high concentrations of salts in the root zone are contributing factors. This study was conducted to determine the effects of summer cultivation treatments on field infiltration rates of water, soil salinity, oxygen diffusion rates (ODR), bulk density, total and air-filled porosity, and root weight density. This research was conducted during two summer seasons (1996 and 1997) on a practice putting green located at Industry Hills Golf Courses, City of Industry, Calif. The green was constructed to U.S. Golf Association (USGA) specifications in 1978. Cultivation treatments consisted of: 1-3) water injection cultivation (WIC) applied with a Toro HydroJect every 21 d (raised position), and every 14 or 21 d (lowered position); 4) solid tine cultivation (STC) applied every 14 d; and 5) no cultivation (check). Results showed WIC and STC significantly increased field infiltration rates of water and lowered overall soil electrical conductivity of the extract (ECe) at depths of 2.5 to 7.5 cm and 7.5 to 15.0 cm in the root zone. The effects of WIC, raised position, did not differ significantly from those of STC, but infiltration rates of water were greater on all rating dates. Cultivation treatments had no significant effects on overall soil ODR, bulk density, and porosity or on overall root weight density.

quality could be maintained with reduced, or even deficit irrigation; an irrigation level below ET crop (Door-Prudent water management on turfgrass is an important issue. enbos and Pruitt, 1984) divided by uniformity of the There is a need to define best management practices (BMPs), including optimal irrigation frequency for tall fescue (Festuca arundinacea irrigation system. Subsequent research at the University Schreb.) when irrigated at a level that would be less than a typical of California sought to provide guidelines for minimum industry practice of ET crop /irrigation uniformity, where ET crop ϭ crop irrigation levels for turfgrass. Meyer et al. (1985) deterevapotranspiration ϭ reference evapotranspiration (ET o ) ϫ crop coefmined accurate monthly K c for warm-and cool-season ficient (K c ). A 2-yr field study was conducted in Riverside, CA, to turfgrasses and stated water conservation effectively determine if the visual quality of tall fescue could be improved during saves 20 to 40% of water needs when 60 to 80% of the warm season by altering irrigation frequency (two, three, or four ET crop is applied. This research, in part, led to the Model irrigation events per week), cultivar selection (a dwarf cultivar, 'Short-Water Efficient Landscape Ordinance, AB325, which stop' or a turf-type cultivar, 'Jaguar III'), and mowing height (3.8 or recommended an annual maximum applied water allow-6.4 cm) when irrigated at 80% ET crop /irrigation uniformity. Volumetric ance of 80% ET o per square foot of landscape. Current soil water content at the 30-, 61-, and 91-cm depths was also measured on each Jaguar III sub-subplot. During the first year, visual quality 2011

Despite problems of low fruit set, small fruit size and alternate bearing, the Hass cultivar dominates commercial avocado production worldwide. To increase yield and fruit size, gibberellic acid (GA 3) (25 mg L −1) was applied at different stages of 'Hass' avocado tree phenology: (i) mid-late April (flower abscission), end of June-beginning of July (fruit abscission and beginning of the exponential phase of fruit growth), and mid-January (beginning of pre-harvest fruit drop); (ii) end of June-beginning of July; and (iii) mid-September (near the end of the major fruit abscission period; period of exponential fruit growth). In both years of the research, applications of GA 3 in April and June-July were within the periods of intense flower and fruit abscission, respectively; fruit abscission was low in September and January. Maximum air temperature was not related to flower or fruit abscission. In the on-crop year (391 fruit per untreated control tree), a single application of GA 3 at the end of June-beginning of July significantly increased total yield (kilograms only) and yield of commercially valuable fruit (178-325 g/fruit) (as kilograms and number per tree) compared with the control (P < 0.0001). GA 3 applied in September increased total yield (kilograms only) and yield of commercially valuable fruit (kilograms and number per tree) to values intermediate to and not significantly different from all other treatments, except trees receiving multiple applications of GA 3. This treatment reduced total yield and yield of commercially valuable fruit (kilograms and number per tree) relative to all treatments (P ≤ 0.0002). In contrast, during the off-crop year (32 fruit per control tree), no GA 3 treatment had a significant effect on yield or fruit size compared with the control and all other GA 3 treatments. For 'Hass' avocado, there was no negative effect from applying GA 3 at the end of June-beginning of July in both the off-and on-crop years; 2-year cumulative total yield and yield of commercially valuable fruit were increased by 27 kg (128 fruit) and 22 kg (101 fruit) per tree, respectively, above the yield of untreated control trees (P < 0.0001).