Low soil nitrate levels from golf course fairways related to organic matter sink for nitrogen

Nitrogen (N) is applied to golf course fairways at rates similar to that applied to corn. This appears excessive since N fertilization of corn is approximately equal to the amount of N removed at harvest, while typically no harvest occurs for turf. This study was done to determine soil nitrate (NO(3)) concentrations from newer and older golf courses and to help determine the fate of fertilizer N. Soil samples were taken every other month in 1995 from two golf courses in southeastern Louisiana to a 3 m depth and from six sites monthly in 1996 to a 1-m depth. In August 1996, soils were also sampled off of the fairways in areas that were similar to the fairways, but were unfertilized. All soils were analyzed for water-extractable NO(3), and a comparison was made of soil organic matter (OM) and N contents from fertilized and unfertilized areas. Results indicated, with few exceptions, low levels of NO(3) throughout the profile, excluding the upper surface soils. Generally, surface soils measured < 15 mg kg(-1) NO(3)-N while soils at depths > 30 cm were < 3 mg kg(-1) NO(3)-N. The fertilized fairways had 0.151% soil N versus the adjacent unfertilized areas of 0.108% N. The fertilized soils had 1,930 kg more N per 30 cm thick hectare slice than did the unfertilized soils' equivalent to 10 years of N fertilization. Organic matter was also higher from the fertilized soils than from the unfertilized soils (1.61% versus 1.03%). It appeared much of the N applied to turf throughout the years had been captured by the OM sink. Prior to golf course development, conditions are generally not as conducive for soil OM buildup as compared to the golf-course regime of adequate N fertilization and no harvests. Some of the high requirement for N of the golf-course fairways of this study were likely related to the N requirement of a soil OM fraction that grew as the golf course aged.