Nitrogen leaching losses from lysimeters containing winter kale: the effects of urinary N rate and DCD application

Abstract

Nitrogen (N) leached from the plant-soil system is an environmental concern. The objective of this study was to quantify N leaching losses from cow urine deposited during grazing of a winter forage crop (kale), and determine the effect of using the nitrification inhibitor dicyandiamide (DCD) to reduce N leaching losses. Fresh cow urine was applied to the surface of large soil monolith lysimeters in late June 2011 at two urinary N deposition rates; 500 and 700 kg N ha−1 (with and without DCD), and compared with losses from lysimeters receiving no urine. Most of the N leaching loss was in the form of nitrate-N (NO3–-N), with an average of 25% leached as ammonium-N (NH4 +-N). Nitrate-N leaching losses were significantly higher under urine-treated lysimeters (213 and 380 kg NO3–-N ha−1 at the 500 and 700 kg N ha−1 rates, respectively) than those without urine (c. 33 kg NO3–-N ha−1). The application of DCD reduced NO3–-N leaching losses by up to 54%. The results indicate that N leaching losses from winter forage crop systems are high and that the application of DCD can reduce these losses.