Effect of Nitrogen Application Rates on Nitrous Oxide Emission during Crop Cultivations in Upland Soil

Abstract

BACKGROUND: Generally, nitrogen (N) fertilization higher than the recommended dose is applied during vegetable cultivation to increase productivity. But higherN fertilization also increases the concentrations of nitrate ions and nitrous oxide in soil. In this experiment, the impact ofN fertilizationwas studied on nitrous oxide (N2O) emission to standardize the optimumfertilization level for minimizing N2Oemission aswell as increasing crop productivity.Herein,we developedN2Oemission inventory for upland soil region during red pepper and Chinese milk vetch cultivation. METHODS AND RESULTS: Nitrogen fertilizers were applied at different rates to study their effect onN2Oemission during red pepper and Chinese milk vetch cultivation. The gas sampleswere collected by static closed chambermethod andN2Oconcentrationwasmeasured by gas chromatography. The total N2Ofluxwas steadily increased due to increasing N fertilization level, though the overall pattern of N2O emission dynamicswas same.Application ofNfertilization higher than the recommended dose increased the values of both seasonal N2O flux (94.5% for Chinese cabbage and 30.7%for red pepper) andN2Oemission per unit crop yield (77.9% for Chinese cabbage and 23.2% for red pepper). Nitrous oxide inventory revealed that theN2Oemissiondue to unit amount of N application from short-duration vegetable field in fall (autumn) season (6.36 kg/ ha) was almost 70% higher than that during summer season. CONCLUSION:Application of excessN-fertilizers increased seasonal N2O flux especially the N2O flux per unit yield during both Chinese cabbage and red pepper cultivation. This suggested that the higher N fertilization than the recommended dose actually facilitates N2O emission than boosting plant productivity. The N2O inventory for upland farming in temperate region like Korea revealed that N2O flux due to unit amount ofN-fertilizer application forChinese cabbage in fall (autumn) season was comparatively higher than that of summer vegetables like red pepper. Therefore,the judicious N fertilization following recommended dose is required to suppress N2O emission with high vegetable productivity in upland soils.