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.