Effects of Different Nitrogen Fertilizer and Biochar Applications on CO2 and N2O Emissions from Upland Soil in the Closed Chamber

Abstract

Carbon dioxide (CO2) and nitrous oxide (N2O) emissions from soil are expected to vary with type of nitrogen fertilizer used. Biochar has recently been proposed as a potential solution to mitigate climate change by reducing greenhouse gas emissions from soils. Incubation experiment was conducted to investigate the effect of different types of biochar on CO2 and N2O emissions when different nitrogen fertilizers used in upland soil. The treatment consisted of different nitrogen fertilizers such as urea, ammonium sulfate and oil cake, and three types of biochars from pear branch, rice hull and soybean stalk. Soil moisture content was adjusted to 70% of the water holding capacity at 25°C. CO2 and N2O gases were collected and analyzed. The cumulative CO2 emissions were 119.4 g m-2 for urea, 107.1 g m-2 for ammonium sulfate, 381.5 g m-2 for oil cake, 137.1 - 154.8 g m-2 for urea + biochars, 114.4 - 161.5 g m-2 for ammonium sulfate + biochars, and 396.9 - 416.4 g m-2 for oil cake + biochars. The cumulative N2O emissions were 216.6 mg m-2 for urea, 44.2 mg m-2 for ammonium sulfate, 347.7 mg m-2 for oil cake and 123.7 - 208.3 mg m-2 for urea + biochars, 39.1 - 114.9 mg m-2 for ammonium sulfate + biochars and 108.9 - 184.2 mg m-2 for oil cake + biochars. No significant differences were observed in N2O emissions among biochar types, except for the mixture of soybean stalk biochar and ammonium sulfate. However, N2O emission was related to both biochar input amount and nitrogen fertilizer types. In particular, N2O reduction effect was great in the addition of biochar when oil cake is mixed into soil. It is considered that further long term field study is needed to apply the biochar use in farming practices. Keywords: Biochar, Carbon dioxide, Nitrogen fertilizer, Nitrous oxide