Direct and indirect nitrous oxide emissions from controlled release and conventional fertilizers applied to potatoes in coarse textures soil.

Abstract

Irrigated potato (Solanum tuberosum L.) production requires significant inputs of fertilizer N for optimal tuber yield and quality. However, high N rates carry the risk of high N loss, particularly in coarse-textured, well-drained soils where potatoes are commonly grown. Polymer coated controlled-release ureas (PCU) have shown promise in reducing NO3 - leaching, a groundwater quality concern, and may potentially also reduce emissions of N2O, a greenhouse gas with nearly 300 times the warming potential of carbon dioxide. However, comparisons of multiple PCUs are uncommon. Studies were conducted over three years to compare N loss (as NO3 - and N2O), yield response, and N use efficiency (NUE) from an unfertilized control, split applied conventional N fertilizer (CSA), and two PCU products (PCU-1 and PCU-2) applied at 270 kg N ha-1 yr-1. Tuber yields, NUE, and leaching did not differ among fertilized treatments. Directly measured N2O emissions were significantly lower with PCU-1 than CSA. Fertilizer induced emissions were relatively low, ranging from 0.10 to 0.49% of applied N. Indirect N2O emissions, estimated using the IPCC default emission factor of 0.75% of NO3 - leached, were significantly lower than direct emissions. However, due to uncertainty, indirect emissions could be anywhere from 0.6 to 84.9% of direct. These results show that PCU can potentially reduce N2O emissions. However, results are product specific and work remains to be done in narrowing the indirect emission factor uncertainty range.