Golf Course Management

DEC 2018

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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Page 68 of 101

12.18 GOLF COURSE MANAGEMENT 65 e goal of a nitrogen fertilizer program should be to optimize plant uptake while minimizing nitrogen losses, such as runoff, leaching and gaseous losses. As stewards of the environment, golf course superintendents should understand how nitrogen moves in the environment and be aware of the importance of preventing nitrogen fertilizer from con taminating groundwaters and surface waters through leaching and runoff and of reducing gaseous losses of nitrogen as well. No single nitrogen fertilizer program is best for all turf. Nitrogen fertilizer programs will vary by turf species, especially between cool and warm season grasses, and among soil conditions (for example, soil type, prop erties, pH, slope, soil water content and soil temperature) and site conditions (for example, environment, climate and site use). erefore, an effective nitrogen fertilizer program incor porates information about the soil and site conditions, the appropriate nitrogen amounts and timing of application, and what happens to the nitrogen fertilizer once it is applied to the turf. Plants absorb nitrogen as both nitrate (NO 3 ) and ammonium (NH 4 + ), and prefer ence for either varies by age and type of plant, environment and other factors. In the turf industry, most of the nitrogen fertilizer is ap plied as urea, which is quickly converted to ammonium by urease, an enzyme found in soils and on the turf. Does all of the nitrogen fertilizer applied get taken up by the plant? No. Why not? Because at the time of fertilizer application, multiple environmental factors and management practices may influence the nitrogen processes on the turf and in the soil, and these practices may result in the loss of nitrogen through multiple nitrogen pathways in the soil plant atmosphere system (Figure 1). Gaseous losses from denitrification One of these nitrogen pathways is denitrifi cation, the process by which denitrifying bac teria convert nitrate into dinitrogen (N 2 ), nitric oxide (NO) and nitrous oxide (N 2 O) gases, which are all released into the atmosphere. Nitrous oxide, an important greenhouse gas associated with global climate change, is re portedly 310 times more effective than carbon dioxide (CO 2 ) at trapping longwave radiation (that is, heat) in the atmosphere, and it is, potentially, the gas that is responsible for the greatest depletion of ozone (6, 10). From 1990 to 2005, agricultural activities (nitrogen fertil ization and soil management) have increased worldwide nitrous oxide emissions by 17% (6, 12). Applications of fertilizer to agricultural land — including turfgrass systems (4, 7, 8) — are responsible for a significant percentage of the nitrous oxide emitted into the atmosphere each year (9). Denitrification typically occurs under an aerobic conditions — wet soil conditions with an absence or limited amount of free oxygen. erefore, an increase in soil moisture during or after nitrogen fertilization may significantly amplify nitrous oxide fluxes. Past research in Figure 2. The automated rainout shelter is activated by 0.01 inch of rain. Photos by Ross Braun

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