In arid climates water is a limited resource, and turfgrass is often irrigated with municipal effluent. However, the effects of continuous turfgrass irrigation with sewage effluent on soil and leachate water quality needs to be evaluated. The objective of this field experiment was to evaluate the effect of secondary treated municipal effluent irrigation on soil and leachate properties under a turf groundcover during the first 16 mo of irrigation. Research plots were irrigated identically with either effluent or potable water using a leaching fraction of approximately 20%. Effluent irrigation resulted in significant changes in soil properties after a relatively short period of time. After 16 mo of use, when compared with potable irrigation, effluent was found to increase electrical conductivity (EC) by 0.5 dS m−1, NO3–N by 7.8 mg kg−1, P by 31.7 mg kg−1, K by 134 mg kg−, Na by 6.0 mmol L−1 and the exchangeable sodium percentage (ESP) by 6.8. Soil Ca + Mg concentrations were greater under effluent irrigation by 0.5 mmol L−1 but decreased during the study period. Soil pH was not significantly different from potable irrigation. Leachates collected at 0.61‐m depth indicated that effluent soil leachates were higher than potable leachates primarily in EC by 0.2 dS m−1 and Na content by 0.8 mmol L−1. The increase did not exceed current recommended limits for drinking water quality.

Effluent and other secondary waters have become important sources of irrigation water in the U.S. Southwest. Information is inadequate relative to potential long‐term effluent irrigation effects on turfgrass and soil chemical quality. The objective of this field research was to determine the influence of secondarily treated municipal wastewater irrigation on the chemical quality of bermudagrass (Cynodon dactylon L.) turf soil (Sonoita gravelly sandy loam: coarse‐loamy, mixed, thermic Typic Haplargid) when compared to similarly irrigated potable water plots. Research plots were irrigated using a 20% leaching fraction. After 3.2 yr of use, effluent water increased soil electrical conductivity by 0.2 ds m−1, Na by 155 mg kg−1, P by 26 mg kg−1, and K by 50 mg kg−1 in comparison to potable irrigated plots. Soil pH was not significantly affected by effluent irrigation. The concentrations of Fe, Mn, Cu, and Zn were found to be within the range considered normal for agricultural soil. Effluent irrigation increased soil total organic carbon and nitrogen during the first 1.3 yr of irrigation only. Total aerobic bacteria populations were similar in all irrigated plots indicating these microbes were not promoted or inhibited by the use of this wastewater. In summary, the irrigation of this turf soil for 3.3 yr with the secondarily treated wastewater used in this study had no serious detrimental effects on soil quality

Irrigation scheduling systems which estimate actual evapotranspiration (ETa) by adjusting reference evapotranspiration (ETo) with crop coefficients (Kcs) have been suggested as a means of improving irrigation management of turfgrass in the desert southwest. The objective of this study was to develop turfgrass Kcs for use with ETo computed by the Penman Monteith Equation recommended by the United Nations Food and Agricultural Organization (FAO). Crop coefficients were developed for fairway quality ‘Tifway’ bermudagrass (Cynodon dactylon L. × C. transvaalinsis Davy) in summer and overseeded ‘Froghair’ intermediate ryegrass (Lolium perenne × L. multiflorum) in winter by relating daily measurements of ETa obtained from weighing lysimeters to ETo computed with meteorological data. Monthly and seasonal Kcs were developed by (i) computing the mean of individual daily Kcs, (ii) dividing cumulative ETa by cumulative ETo for the period, and (iii) computing the slope of least squares regression lines relating ETa to ETo. The three computation procedures did not greatly affect the resulting Kc value. Bermudagrass Kcs ranged from 0.78 in June to 0.83 in September, with monthly variation related to turf growth rate. Use of a constant Kc of 0.80 would suffice for estimating ETa in summer. Monthly Kcs for intermediate ryegrass ranged from 0.78 in January to 0.90 in April and varied in relation to mean air temperature. Increased bulk surface resistance resulting from chill‐induced reductions in stomatal conductance and/or a reduction in turf growth rate and leaf area index may lower ETa and Kcs during the colder winter months, making use of a constant seasonal Kc less suitable in winter. An inverse linear relationship was obtained between the coefficient of variation of mean monthly Kc and the ratio of measured to theoretical clear sky solar radiation, indicating Kcs are less reliable during periods of cloudy weather.

No abstract

Combining frequent N applications and irrigations for turfgrasses grown in sandy soils is a common occurrence on golf course putting greens. A greenhouse study was conducted to determine leaching losses of nitrate and ammonium nitrogen from `Penncross' creeping bentgrass (Agrostis palustris L.) growing on an 80 sand:20 peat soil mixture following frequent, moderately heavy irrigations and light or moderate N fertilizer applications. Nitrogen sources included calcium nitrate, ammonium nitrate, ammonium sulfate, urea, urea formaldehyde and isobutylediene diurea. Application levels were 9.76 kg N/ha per 7 days and 19.52 kg N/ha per 14 days for 10 weeks. Irrigation equivalent to 38 mm·week-1 was applied in three equal applications. Overall, 46% of the applied water leached. Total leaching losses were <0.5% of the applied N. Nitrate represented the major portion of the leached N, with ammonium losses being negligible. There were no differences between sources when applied at these levels. In a second study, a single 48.8 kg N/ha application resulted in higher leaching losses of N, but only calcium nitrate and ammonium nitrate had total losses > 2% (2.80% and 4.13%, respectively, over an n-day period). Nitrate concentrations were found to exceed 45 mg·liter-1 for ammonium nitrate.