INTERNATIONAL SYMPOSIUM TOWARDS SUSTAINABLE LIVELIHOODS AND ECOSYSTEMS IN MOUNTAINOUS REGIONS 7-9 March 2006, Chiang Mai, Thailand Tracking methane and nitrous oxide emissions in hedgerow systems in the Philippine uplands D.B. Magcale-Macandog 1 , E.R. Abucay 1 , R.N. Miole 2 , E.L. Abas 3 , R.G. Visco 1 , G.M. Comajig 4 and A.D. Calub 4 1 University of the Philippines Los Baños, Colllege, Laguna, 2 Mindanao State University, Lanao del Sur, 3 Cotabato Foundation College of Science & Technology, South Cotabato 4 and UPLB Foundation Inc., Philippines 1 Introduction Two important N oxides are produced in agricultural soils: nitrous oxide (N 2 O) and nitric oxide (NO). Agricultural soils are the most important anthropogenic source of this gas contributing 6.2 Tg N yr -1 , about 78 % of the N emissions from anthropogenic activities (Kroeze et al., 1999). Both nitrous oxide (N 2 O) and nitric oxide (NO) are by-products of the same microbial processes in soils, nitrification and denitrification. The study site, Claveria, a municipality of Misamis Oriental, Mindanao has an area of about 82,500 hectares. It is located on a plateau ascending abruptly from the west with elevation of 350 masl to 1,200 masl in the east. It has a rugged topography, characterized by rolling hills and mountains. The climate in the area has a pronounced dry season from January to May (<100 mm/mo) and wet season from June to December (>200 mm/mo). Soils in the area are derived from pyroclastic materials and classified as acidic-upland with a depth of more than 1 m. 2 Methodology One- and seven-year old E. deglupta and G. arborea hedgerow systems were established and selected, respectively, for use in the study. The treatments used in the study are different combinations of tree species, tree age, and tree spacing (Table 1). Seeds of maize (Pioneer hybrid 3014) were planted in the alley areas at 1 seed per hill. The planting distance between furrows was 60 cm and 25-30 cm between rows. Weeding of the alleys and inter row cultivation of maize plants were done 30 DAP. Table 1: The experimental treatments (tree species, tree age, spacing) and number of replicates employed in the study Experiment No. 1 (7 year-old trees, 2 replicates per treatment) Experiment No. 2 (1 year-old trees, 3 replicates per treatment) Control for G. arborea, pure maize (Zea mays) 1 x 3 m (G. arborea + Z. mays) 1 x 9 m (G. arborea + Z. mays) Control for E. deplupta, pure maize (Z. mays) 1 x 3 m (E. deglupta + Z. mays) 1 x 9 m (E. deglupta + Z. mays) Control, pure maize (Z. mays) 1 x 1 m (Pure G. arborea) 1 x 3 m (G. arborea + Z. mays) 1 x 9 m (G. arborea + Z. mays) 1 x 1 m (Pure E. deglupta) 1 x 3 m (E. deglupta + Z. mays) 1 x 9 m (E. deglupta + Z. mays)