EMISI METANA PADA LAHAN PADI SAWAH ORGANIK DI SRAGEN

Mujiyo, Prof. Dr. Ir. Bambang Hendro S., SU

2013 | Disertasi | S3 Ilmu Tanah

Sistem padi sawah organik mutlak menggunakan pupuk organik, yang dinilai dapat meningkatkan produksi gas metana (CH4). Azolla merupakan sumber pupuk organik dan berpengaruh menurunkan emisi CH4 dari tanah sawah. Penelitian ini bertujuan untuk: (1) Mengetahui perbedaan sifat tanah dan produksi CH4 pada sawah organik, semi organik dan konvensional, dan mengetahui sifat tanah yang mempengaruhi potensi emisi CH4, (2) Mengetahui pengaruh pupuk kandang sapi, pupuk Azolla (dibenamkan), inokulum Azolla (ditumbuhkan bersama tanaman padi) dan kombinasinya terhadap sifat tanah, pertumbuhan dan hasil tanaman padi, dan emisi CH4, dan (3) Menentukan rekomendasi penggunaan dan cara aplikasi pupuk kandang sapi dan Azolla yang dapat memperbaiki sifat tanah, meningkatkan hasil tanaman padi, dan menurunkan emisi CH4. Penelitian dilaksanakan dengan 3 tahap: (1) Karakterisasi lahan dan analisis potensi produksi CH4 di laboratorium. Sifat tanah sawah organik diperbandingkan dengan sawah semi organik dan konvensional. Potensi produksi CH4 ditentukan dengan mengukur CH4 oleh tanah yang diinkubasi dengan genangan, (2) Percobaan rumah kaca untuk penanaman padi sawah organik menggunakan berbagai perlakuan. Perlakuan menggunakan pupuk kandang sapi, pupuk Azolla, inokulum Azolla, dan kombinasinya didasarkan pada pemenuhan 120 kg N ha-1, dan (3) Percobaan lapangan untuk penanaman padi sawah di lahan organik, menggunakan perlakuan yang sama dengan percobaan rumah kaca. Hasil penelitian menunjukkan bahwa sifat tanah sawah organik berbeda dengan tanah sawah semi organik dan konvensional. Tanah sawah organik mempunyai warna matriks lebih gelap, dan C-organik, konsentrasi massa humus, C dan N biomassa mikrobia, dan potensi produksi CH4 lebih tinggi dari pada tanah sawah semi organik dan konvensional. Sifat tanah yang paling mempengaruhi emisi CH4 adalah kandungan C-organik. Pupuk kandang sapi dan pupuk Azolla meningkatkan hasil gabah kering panen (GKP) berturut-turut sebesar 14,77% dan 9,24%, tetapi tidak berpengaruh nyata terhadap emisi CH4. Inokulum Azolla menurunkan emisi CH4 sebesar 52,91%, tetapi tidak berpengaruh nyata terhadap GKP. Penggunaan pupuk kandang sapi 4 ton ha-1 + inokulum Azolla 2 ton ha-1, pupuk Azolla 2,5 ton ha-1 + inokulum Azolla 2 ton ha-1, dan pupuk kandang sapi 2,67 ton ha-1 + pupuk Azolla 1,67 ton ha-1 + inokulum Azolla 1,33 ton ha-1 dapat meningkatkan GKP dan menurunkan emisi CH4. Penggunaan inokulum Azolla dapat diterapkan sebagai salah satu cara untuk menurunkan emisi gas rumah kaca CH4 pada budidaya padi sawah organik.

Organic paddy system absolutely uses organic fertilizer which assessed can increase the methane (CH4) production. Azolla is organic fertilizer source and affects to reduce CH4 emission from paddy field. This research aimed to: (1) Know the differences of soil properties and CH4 production potential in organic paddy field, semi-organic and conventional, and to know the soil property which most influences CH4 emission potential, (2) Know the influence of cow manure, Azolla fertilizer (incorporated into the soil), Azolla inoculum (dual cropping with the rice plant) and its combination to the soil properties, the growth and yield of rice plant, and CH4 emission, and (3) Decide recommendation and the way to applicate cow manure and Azolla which can improve soil properties, increase rice yield, and reduce CH4 emission. This research was conducted into 3 steps: (1) Field characterization and analyzing of CH4 production potential in laboratory. Soil properties in organic paddy field were compared to semi-organic and conventional paddy field. CH4 production potential was determined by measuring CH4 by means of soil which incubated with puddle, (2) Greenhouse experiment for planting organic paddy using various treatments. Treatments using cow manure, Azolla fertilizer, Azolla inoculum, and its combination based on requirement of 120 kg N ha-1, and (3) Field experiment for planting paddy in organic field using some treatments as in greenhouse experiment. The result of the research showed that soil properties of organic paddy field were different from the soil of semi-organic and conventional. Soil in the organic paddy field had darker matrix color, and C-organic, humus mass concentration, microbial biomass C and N, and CH4 production potential were higher than the soil in semi-organic and conventional paddy field. Soil property which most influences CH4 emission was C-organic content. Cow manure and Azolla fertilizer increased the harvest dry grain (HDG) 14.77% and 9.24%, respectively, but did not significantly affect CH4 emission. Azolla inoculum reduced CH4 emission 52.91%, but did not significantly affect HDG. The application of cow manure 4 tons ha-1 + Azolla inoculum 2 tons ha-1, Azolla fertilizer 2.5 tons ha-1 + Azolla inoculum 2 tons ha-1, and cow manure 2.67 tons ha-1 + Azolla fertilizer 1.67 tons ha-1 + Azolla inoculum 1.33 tons ha-1 could increase HDG and reduce CH4 emission. The application of Azolla inoculum can be applied as a way to reduce greenhouse gas emission of CH4 in organic paddy cultivation.

Kata Kunci : emisi CH4, sawah organik, Azolla