Fertilizer Management Effects on Nitrate Leaching and Indirect Nitrous Oxide Emissions in Irrigated Potato Production

摘要

Potato (Solanum tuberosum L.) is a N-intensive crop, with high potential for nitrate (NO3-) leaching, which can contribute to both water contamination and indirect nitrous oxide (N2O) emissions. Two approaches that have been considered for reducing N losses include conventional split application (CSA) of soluble fertilizers and single application of polymer-coated urea (PCU). The objectives of this study were to: (i) compare NO3- leaching using CSA and two PCUs (PCU-1 and PCU-2), which differed in their polymer formulations, and (ii) use measured NO3- leaching rates and published emissions factors to estimate indirect N2O emissions. Averaged over three growing seasons (2007-2009), NO3- leaching rates were not significantly different among the three fertilizer treatments. Using previously reported direct N2O emissions data from the same experiment, total direct plus indirect growing season N2O emissions with PCU-1 were estimated to be 30 to 40% less than with CSA. However, PCU-1 also resulted in greater residual soil N after harvest in 2007 and greater soil-water NO3- in the spring following the 2008 growing season. These results provide evidence that single PCU applications for irrigated potato production do not increase growing season NO3- leaching compared with multiple split applications of soluble fertilizers, but have the potential to increase N losses after the growing season and into the following year. Estimates of indirect N2O emissions ranged from 0.8 to 64% of direct emissions, depending on what value was assumed for the emission factor describing off-site conversion of NO3- to N2O. Thus, our results also demonstrate how more robust models are needed to account for off-site conversion of NO3- to N2O, since current emission factor models have an enormous degree of uncertainty.