NOTE: At the time of publication, the author David J. Wehner was affiliated with the University of Illinois at Urbana-Champaign. Currently, April 2008, he is Dean of the College of Agriculture, Food and Environmental Sciences at California Polytechnic State University - San Luis Obispo.
Denitrification may represent an important mechanism in the fate of N applied to turf. Denitrification losses were directly measured from fertilized 'Baron' Kentucky bluegrass (Poa pratensis L.) sod samples sealed in acrylic chambers using the acetylene inhibition technique. Losses were correlated with soil texture, percent soil saturation (SAT), and temperature. Losses from turf on a Hadley silt loam soil and Hadley silt soil (both coarse-silty, mixed, nonacid, mesic Typic Udifluvents) incubated at 22°C did not exceed 0.4 and 0.1%, respectively, of the applied potassium nitrate fertilizer (4.5 g N m-2) when soil water levels were less than 75% saturated. Soil saturation increased denitrification losses from the silt loam and silt soils to 2.2 and 5.4% of the applied N, respectively. The relationship between percent soil saturation and denitrification loss was quadratic and highly significant for both soils. The equations are: milligrams of N2O – N m-210 d-1 = 1432.50 – 38.96 (percent SAT silt soil) + 0.26 (percent silt soil)2 or 130.80 -5.40 (percent SAT silt loam soil) + 0.05 (SAT silt loam soil)2. A linear relationship [milligrams of N2O m-2 10 d-1 = 0.49(°C) – 9.70] existed between denitrification losses and soil temperatures between 22 and 30°C in the silt soil at 75% of soil saturation. Soil temperatures of 30°C or greater coupled with saturated soil conditions resulted in the greatest losses, equivalent to 44.6 and 92.6% of the applied N to the silt loam and silt soils, respectively. Denitrification losses did not increase at soil temperatures above 30°C. These results indicate that denitrification loss from fertilizers applied to turfgrasses may not be a serious problem unless the soils are saturated and at higher soil temperatures.
Agronomy and Crop Sciences