Tropentag, September 19 - 21, 2012 in Göttingen "Resilience of agricultural systems against crises"

Methane and Nitrous Oxide Emission from the System of Rice Intensification (SRI) under Rainfed Lowland Ecosystem in Cambodia

University of Copenhagen, Faculty of Life Sciences, Dept. of Agriculture and Ecology, Denmark

Abstract

The system of rice intensification (SRI) receives considerable attention for its potentials to increase rice productivity in marginalised rice-growing environment. SRI differs from conventional rice management by several parameters, including water management. The intermittent irrigation (as opposed to permanent flooding) under SRI was carried out in order to improve soil aeration, root activities, reduce ineffective tillers and remove toxic substances. This practice may significantly reduce methane (CH₄) emissions, a potent greenhouse gas. However, this benefit may be offset by increased nitrous oxide (N₂O) emissions, which has much higher radiation absorbing capacity. The present field study measured the fluxes of CH₄ and N₂O under SRI practices and compared the emission of greenhouse gases from SRI with a Conventional Management Practices (CMP) production system under which continuous flooding was applied. The effects of nutrient amendment (composted farmyard manure (FYM), mineral fertiliser (MF) and FYM+MF) were also investigated under each production system. The results indicated large seasonal variations of CH₄ patterns during the growing season with a peak emission of about 1300 mg CH₄ m^-2 d^-1 under both production systems two weeks after rice transplanting. N₂O emissions were not detected in any treatments, which indicates NO₃^- and available C were limiting in the field trial. Under each production system, the highest emission of CH₄ was under FYM+MF treatments (282 kg CH₄ emission ha^-1 under CMP and 213 kg ha^-1 CH₄ emission under SRI). Total CH₄ emission under SRI practices was reduced by 22% in FYM treatment, 17% in MF treatment and 24% in FYM+MF treatment compared to CMP practices. There was no effect of water management on CH₄ emission in the non-fertilised control. Grain yields were not significantly affected by the production system. Thus the CO₂-equivalent emitted per kg grain produced is lower under SRI than CMP, namely 21% in FYM treatment, 8% in MF treatment and 21% in FYM+MF treatment, respectively. The results therefore suggest a potential of SRI to mitigate the greenhouse gas emission from rice production without compromising rice yields.

Keywords: Cambodia, methane, nitrous oxide, nutrient, system of rice intensification, water management, rice

Contact Address: Proyuth Ly, University of Copenhagen, Faculty of Life Sciences, Dept. of Agriculture and Ecology, Thorvaldsensvej 40 3rd Floor, 1871 Frederiksberg C, Denmark, e-mail: proyuthlife.ku.dk