Experiments to document the long-term effects of clipping management on N requirements, soil organic carbon (SOC), and soil organic nitrogen (SON) are difficult and costly and therefore few. The CENTURY ecosystem model offers an opportunity to study long-term effects of turfgrass clipping management on biomass production, N requirements, SOC and SON, and N leaching through computer simulation. In this study, the model was verified by comparing CENTURY-predicted Kentucky bluegrass (Poa pratensis L.) clipping yields with field-measured clipping yields. Long-term simulations were run for Kentucky bluegrass grown under home lawn conditions on a clay loam soil in Colorado. The model predicted that compared with clipping-removed management, returning clippings for 10 to 50 yr would increase soil C sequestration by 11 to 25% and nitrogen sequestration by 12 to 28% under a high (150 kg N ha(-1) yr(-1) nitrogen (N) fertilization regime, and increase soil carbon sequestration by 11 to 59% and N sequestration by 14 to 78% under a low (75 kg N ha(-1) yr(-1)) N fertilization regime. The CENTURY model was further used as a management supporting system to generate optimal N fertilization rates as a function of turfgrass age. Returning grass clippings to the turf-soil ecosystem can reduce N requirements by 25% from 1 to 10 yr after turf establishment, by 33% 11 to 25 yr after establishment, by 50% 25 to 50 yr after establishment, and by 60% thereafter. The CENTURY model shows potential for use as a decision-supporting tool for maintaining turf quality and minimizing negative environmental impacts.

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T he notion that water quality problems caused by soluble salts arise only-or even primarily-in regions with arid climates is far from the truth. For example, the excessive pumping of fresh water from wells in coastal areas can lead to saltwater intrusion problems. Even in high-rainfall areas the groundwater may contain significant levels of soluble salts derived from underground rock formations of marine origin. Moreover, increasing numbers of golf courses, parks, cemeteries, school campuses, industrial, and commercial turfed sites use potentially saline recycled municipal water for irrigation. The result of this breadth of use is that the effects of excess soluble salts are visible on turfgrass plantings in a wide range of climates. Water analysis and periodic monitoring have thus become key components of sound irrigation management.Water analysis by a commercial laboratory provides data on many parameters, some of which are of little significance for turfgrass irrigation. The most important parameters for turfgrass management are total concentration of soluble salts (salinity); sodium (Na) content; relative proportion of sodium to calcium (Ca) and magnesium (Mg) (Sodium Adsorption Ratio or SAR); chloride (Cl), boron (B), bicarbonate (HCO 3 ), and carbonate (CO 3 ) content; and pH. Other parameters that you are likely to find on a water test report and that you should review are nutrient content (nitrogen, phosphorus, and potassium), chlorine content, suspended solids, and turbidity, though none of these by itself plays a major role in determining the suitability of water for irrigation.