NITROUS OXIDE EMISSIONS AT SEVERAL SITES OF ORGANIC AND CONVENTIONAL FIELDS IN YOGYAKARTA AND CENTRAL JAVA

FIRMANSYAH W H, Dr. Ir. Benito Heru Purwanto, MP., M.Agr. ; Prof. Dr. Ir. Azwar Maas, M.Sc.

2014 | Skripsi | ILMU TANAH

Pertanian dengan sistem padi tergenang dianggap sebagai salah satu sumber emisi gas N2O (dinitrogen oksida). Dinitrogen oksida tercatat sebagai penyumbang gas rumah kaca (GRK) sebesar 10%, dengan hampir 90% dari emisi ini berasal dari praktek-praktek pertanian. Terlepas dari isu-isu kesehatan, isu lingkungan juga menjadi salah satu alasan masyarakat pertanian untuk menggunakan sistem organik. FAO sendiri mempromosikan pertanian organik sebagai salah satu solusi untuk mengurangi emisi CH4 dan N2O. Penelitian emisi N2O ini menggunakan metode chamber. Gas dan tanah sampel diambil di tiga lokasi, Imogiri, Godean dan Sawangan. Setiap lokasi memiliki dua lokasi pengambilan sampel, organik dan konvensional. Sampel diambil empat kali selama satu musim, sebelum pindah tanam (BT), dua minggu setelah tanam (2AT), antara fase vegetatif dan generatif (MS), dan dua minggu sebelum panen (2BH). Penelitian ini menunjukkan bahwa dua dari tiga lokasi yang digunakan untuk penelitian, pertanian organik berhasil mengurangi emisi gas dinitrogen oksida. Godean menunjukkan emisi 138 g N2O/m2/jam untuk pertanaman organik dan 336 mg N2O/m2/jam untuk pertanaman konvensional. Sawangan menunjukkan emisi 348 g N2O/m2/jam untuk pertanaman organik dan 444 mg N2O/m2/jam untuk pertanaman konvensional. Namun, pertanaman organik di Imogiri menunjukkan emisi N2O yang lebih tinggi (480 mg N2O/m2/jam) dibandingkan pertanaman konvensional (402 mg N2O/m2/jam). Walaupun t-test yang dilakukan terhadap data menunjukkan hanya satu dari tiga lokasi memperlihatkan signifikansi pertanian organik dalam mengurangi emisi gas N2O, tetapi pertanian organik dapat mengurangi emisi gas ini hingga 20% secara rata-rata. Analisis korelasi menunjukkan bahwa emisi gas N2O memiliki hubungan yang signifikan dengan N-total di pertanaman organik Imogiri, sedangkan suhu dan NO3- di pertanaman konvensional Imogiri, di pertanaman organik Godean, suhu dan NO3- di pertanaman organik Godean, Suhu di pertanaman konvensional sawangan, pH H2O dan pH KCl di pertanaman organik Sawangan dan potensial redox di pertanaman konvensional Sawangan. Apabila kita abaikan lokasi penelitian, maka baik pertanaman organik maupun konvensional tidak menunjukan korelasi yang kuat antara emisi N2O dengan parameter tanah yang diukur. Meskipun harus ada modifikasi dan perkembangan dalam manajemen pertanaman organik, namun penelitian ini telah menunjukkan kepada kita bahwa pertanian organik di lahan sawah memiliki potensi yang lebih menjanjikan untuk mengurangi emisi gas N2O dibandingkan pertanian konvensional.

Agriculture with flooded paddy farming is considered as one of N2O (nitrous oxide) emissions source. Nitrous oxide emissions account for about 10% of global greenhouse gas emissions, with almost 90% of these emissions derived from agricultural practices. Apart from the health issues, environmental issues also become one of the reason of agricultural community to use organic system. FAO themselves promoted organic agriculture as one solution to reduce CH4 and N2O emissions. This research of N2O emissions uses chamber method. Gas and soil samples were taken at three locations, Imogiri, Godean and Sawangan. Each location has two sampling sites, organic and conventional. Samples were taken four times during a season, before transplanting (BT), two weeks after transplanting (2AT), between vegetative and generative stage (MS), and two weeks before harvesting (2BH). This study shows that in two of three sites used for research, organic farming are successfully mitigate the emissions of nitrous oxide gas. Godean site shows emission of 138 �µg N2O/m2/hour for organic field and 336 �µg N2O/m2/hour for conventional field. Sawangan site shows emission of 348 �µg N2O/m2/hour for organic field and 444 �µg N2O/m2/hour for conventional field. However, organic field of Imogiri shows higher nitrous oxide gas emision (480 �µg N2O/m2/hour) than conventional field (402 �µg N2O/m2/hour). Although t-test that is done to the data showed only one of three sites proves significant affect of organic management in order to mitigate nitrous oxide gas emission, but organic farming able to reduce the emission of nitrous oxide gas up to 20% on average. Correlation analysis shows that nitrous oxide gas emission has significant correlation with total-N in organic field of Imogiri, while temperature and NO3- in conventional field of Imogiri, temperature in organic and conventional field of Godean, pH H2O and pH KCl in organic field of Sawangan and oxidation reduction potential (Eh) in conventional field of Sawangan. Though there are modifications and developments will be needed in this management, but this study showed us already that organic farming in paddy fields might has promising potential to mitigate nitrous oxide gas emission than conventional farming.

Kata Kunci : Chamber method, Organic farming, Nitrous oxide gas, Paddy field, Soil