Combination of Methanotrophic Bacteria, Nitrous Oxide Reducing Bacteria, and N2 Fixing Bacteria as Biofertilizer and Greenhouse Gases Reducing Agent in Paddy
Kombinasi Bakteri Metanotrof, Pereduksi Dinitrogen Oksida, dan Penambat Nitrogen sebagai Agen Pereduksi Gas Rumah Kaca dan Pupuk Hayati pada Tanaman Padi
Abstract
High CH4 oxidation activity was found in methanotrophic bacteria (BGM 1, BGM 5, BGM 9, and SKM 14) isolated from paddy fields in Bogor and Sukabumi. Other bacteria, BL1 and BL2, are denitrifier that possess high N2O reduction activity. Those isolates combined with nitrogen (N2) fixing bacteria (Azotobacter sp. and Azospirillum sp.) could be used as biofertilizer to reduce CH4 and N2O emissions and enhance paddy’s growth. The objective of this research was to evaluate the effectiveness of those bacterial combinations as biofertilizer and greenhouse gases reducing agent in paddy. This research was consisted of two experiments. The 1st experiment was arranged in a completely randomized design (CRD) with four replicates and consisted of fertilizer types (inorganic and bacteria) and watering system (submerged and periodically intermittent) treatments. The 2nd experiment was arranged in CRD with four replicates that consisted of bacterial fertilizer types, types of inorganic fertilizer dosages, and watering system factor (submerged and periodically intermittent). The result of the 1st experiment showed that the plant height was not affected by the treatment. Plant fresh weight, dry weight, number of productive tiller, grain per panicle were affected by type of fertilizer. Inorganic fertilizer increased CH4 flux and bacterial fertilizer reduced CH4 flux from paddy field. The best reduction of CH4 flux achieved by bacterial fertilizer contained BGM 1 and BGM 5 isolates. The result of the 2nd experiment showed that combination of BGM 5 – BGM 9 isolates and N2 fixing bacteria enhanced paddy vegetative and generative growth under N fertilizer with the dosage of 166.67 or 250 kg/ha. There was no clear pattern in the CH4 and N2O flux reduction from paddy under bacterial fertilizer application. In general, methanotrophic bacteria and N2O reducing bacteria isolates could reduce CH4 and N2O flux in certain dosage of inorganic fertilizer. In addition, CH4 flux was decreased and N2O flux was increased in periodically intermittent condition.