EFFECT OF PROLONGING MIDSEASON DRAINAGE AND GREEN MANURE APPLICATION ON N2O EMISSION FROM PADDY FIELD IN JAPAN

NUKHAK NUFITA SARI, Dr. Ir. Benito Heru Purwanto, M.P., M.Agr; Dr. Ir. Eko Hanudin, M.S.; Dr. Yo Toma

2017 | Tesis | S2 Ilmu Tanah

N2O merupakan gas rumah kaca antropogenik di atmosfer yang sangat penting setelah CO2 dan CH4. Emisi N2O dari lahan sawah dianggap sebagai salah satu sumber penting N2O di atmosfer. Pengelolaan air, seperti midseason drainage (pengeringan tengah musim), dan aplikasi green manure (pupuk hijau) merupakan faktor penting yang mempengaruhi emisi N2O dari lahan sawah. Oleh karena itu, penelitian ini dilakukan untuk mengetahui pengaruh perpanjangan midseason drainage dan aplikasi green manure terhadap emisi N2O dari lahan sawah, kemudian dampaknya terhadap potensi pemanasan global (global warming potential). Fluks N2O diukur dengan metode closed chamber. Gas diambil dengan spet kemudian disimpan di botol vakum pada menit ke 0, 30, dan 60 pada fallow season (musim bera), dan pada menit 4, 14, dan 24 pada growing season (musim pertumbuhan padi), setelah chamber dibenamkan. Konsentrasi gas N2O dianalisis dengan gas chromatograph. Fluks N2O diukur setiap dua minggu sekali. Sampel tanah diambil pada kedalaman 0-10 cm dari permukaan tanah pada saat pengukuran gas dilakukan, kemudian diukur pH tanah, Eh tanah, NO3-, dan NH4+. Fluks N2O berkorelasi nyata/signifikan dengan pH dan Eh tanah. Fluks N2O berkorelasi secara negatif dengan pH tanah dan berkorelasi positif dengan Eh tanah. Dampak perpanjangan midseason drainage terhadap emisi N2O tahunan terbatas karena besarnya sumbangan N2O selama fallow season daripada growing season. Meskipun demikian, perpanjangan masa midseason drainage berpotensi meningkatkan emisi N2O. Pembenanam tanaman legum sebagai green manure cenderung meningkatkan emisi N2O. Dibandingkan dengan perlakuan tanpa green manure, aplikasi green manure meningkatkan emisi N2O tahunan. Kombinasi dari perpanjangan midseason drainage dan aplikasi green manure cenderung meningkatkan emisi N2O dari lahan sawah sehingga memicu meningkatnya potensi pemanasan global.

N2O is the third most important anthropogenic greenhouse gas in the atmosphere after CO2 and CH4. N2O emission from paddy field has been regarded as one of the important source of atmospheric N2O. Water management, such us midseason drainage, and green manure application are an important factors affecting N2O emission from paddy field. Thus this experiment was conducted to find out effect of prolonged midseason drainage and green manure application on N2O emission from paddy field, then its impact on global warming potential. Fluxes of N2O gas was measured by the closed chamber method. Gas samples were collected by syringe then kept into vacuum-sealed vials with butyl rubber stoppers at 0, 30, and 60 minutes in the fallow season and 4, 14, and 24 minutes in growing season from the time the chambers were deployed. Concentrations of N2O were analyzed by a gas chromatograph (GC) equipped with an electron capture detector. N2O gas fluxes were measured every two weeks. Soil samples were collected from the 0-10-cm depth at the time of each gas sampling measurement. Then soil pH, soil Eh, NO3-, and NH4+ were analyzed from those soil samples. Compare to other soil properties, N2O flux has a significantly correlation with soil pH and soil Eh. N2O fluxes was negatively correlation with soil pH and positively significant correlation with soil Eh. Effect of prolonged midseason drainage period on annual N2O emsision was limited due to the higher contribution of N2O emission in fallow season than growing season to the annual N2O emission. However, prolonged midseason drainage potentially increase N2O emission. Incorporation of legume crop as green manure to the soil tended to increase N2O emission in this study. Compared to the treatment without green manure, application of green manure increased the annual N2O emission. Combination of prolonged midseason drainage and green manure application tended to increase N2O emission from paddy field thus induced the increasing of global warming potential.

Kata Kunci : N2O flux, N2O emission, paddy field, midseason drainage, green manure