Nitrous Oxide and Carbon Dioxide Emissions From Paddy Soil Treated With Rice Husk Products at Different Moisture Contents in a Short-Term Experiment

Abstract

A short-term study was conducted to investigate the effects of additions of rice husk products on nitrous oxide (N2O) and carbon dioxide (CO2) emissions from paddy soil at different soil moisture contents. Soil amended with raw rice husk (RR, 2% on a dry weight basis), rice husk char (RC, 2%), rice husk ash (RA, 2%) or no amendment (CT) was incubated at 40%, 60%, or 80% water-holding capacity (WHC) in a 100-mL bottle for 120 h. Results showed that N2O emission was lower at 40% WHC compared with other WHC treatments. At 60% and 80% WHC, N2O emissions peaked at 24 h of incubation in most treatments. The highest emission of N2O was recorded in the RR addition at 80% WHC. Additions of RC and RA decreased cumulative N2O emissions from soil at 24 h (by 24% at 60% WHC and 51% at 80% WHC for RC, and 90% at 60% WHC and 80% WHC for RA) compared with the CT treatment. Regardless of the soil moisture content, RR enhanced cumulative CO2 emission for 120 h, whereas no significant difference was detected among RC, RA and CT treatments (P > 0.05). Our short-term results indicated that application of rice husk char or ash to soil reduced N2O emission, whereas direct incorporation of rice husk into soil enhanced CO2 and N2O emissions.