Tropentag, September 11 - 13, 2024, Vienna "Explore opportunities... for managing natural resources and a better life for all"

Fertiliser management effect on rice growth and CH₄ emissions in lowland paddy rice in Madagascar

¹University of Antananarivo, Lab. des Radioisotopes, Madagascar
²Japan International Research Center for Agricultural Sciences, Crop, Livestock, and Environment, Japan

Abstract

Rice fields are a major source of CH₄ emissions, a potent greenhouse gas responsible for 0.6°C of global warming. Recent rice intensification and expansion in Africa have contributed to the rise in CH₄ emissions, which account for 7% of global emissions. In Madagascar, rice is a staple food and the third largest rice producer in Africa. However, rice production is still limited in fulfiling the entire population's needs due to low soil nutrient availability. Conventional organic amendments and mineral fertilisers can enhance soil nutrients and rice growth. However, fertiliser management can stimulate CH₄ production by providing a carbon source for the CH₄-producing bacteria. The potential CH₄ emissions from fertiliser management in a tropical context are not well known. To assess the effect of fertiliser management on CH₄ emissions and rice production, a pot experiment with farmyard manure (FYM: 10 t ha^-1), P-broadcasting (60 kg P ha^-1), and control (no fertiliser), and a field experiment with FYM (10 t ha^-1) and N:P:K (45:45:45 kg ha^-1) were conducted. In the pot experiment, low rice growth under control resulted in low rice yield and CH₄ emissions. Meanwhile, FYM and mineral fertiliser significantly increased CH₄ emissions by 84.8% and 71%, respectively, compared to the control. Compared to FYM, mineral fertiliser reduced CH₄ emissions by 7.47% while increasing grain yield two fold. Field experiments further confirmed that mineral fertiliser had lower CH₄ emissions (133.4 kg ha^-1) than FYM (185.3 kg ha^-1). However, rice yield increase by mineral fertiliser over FYM was minimal (0.27 t ha^-1) and not significant. In both experiments, high CH₄ emissions under FYM would mainly be attributed to the high carbon input into the flooded rice fields, which is a major carbon substrate for methanogenic bacteria in CH₄ production. The results also showed that mineral fertiliser significantly reduced greenhouse gas intensity (CH₄ emissions per unit grain yield) compared to FYM due to low CH₄ emissions while improving rice yield. In conclusion, mineral fertiliser application decreased CH₄ emissions while increasing rice productivity, illustrating its environmental and agronomic potential in climate change mitigation and food security.

Keywords: Fertiliser management, greenhouse gas intensity, methane, nutrient deficient soils , rice yield

Contact Address: Lalaina Andrianarijaona, University of Antananarivo, Lab. des Radioisotopes, Lot iie 8bis ae Ambohimirary Route d'Andraisoro, Antananarivo, Madagascar, e-mail: lalaina.andrianarijaonagmail.com