Potential capacity of legume crops as a green manure for rice crop and carbon mineralization

English. Three experiments, namely incubation experiment (in laboratory), greenhouse experiment and field experiment were conducted to study effect of plant material of legume crops as a green manure on the soil fertility and rice production. Latosol soil originated from Muara Experimental Station, Bogor was used in the experiment. 14C isotope was used as a tracer to study carbon mineralization of plant material in the soil. Four kinds of legume crops i.e. long bean, cow pea, mung bean, and pigeon pea were cultivated by full and minimum tillage. The first three legume crops were harvested at two months after planting while the pigeon pea was harvested at 3.5 months after planting (after the first mature fruits were picked) and the plant materials were used as a green manure for the rice growth. The incubation experiment was carried out using CO2 trapping method in a system consisted of 4 interconnected Erlenmeyers. Atomia IV rice variety was used in the greenhouse and field experiments. In the incubation experiment the release of CO2 were observed. While for the pot experiment, parameters observed were ammonium-N, nitrate-N, and mineral-N content; total-N, total-P, organic-C, total-K, and the undecomposed plant material in the soil. For the field experiment dry weight of rice grain were observed. Result of these experiment showed that the rate of CO2-14 released (percent CO2-14/day) from the soil which was treated with long bean material was higher than CO2 released from the soil which were treated with other three legume plant materials. Nutrient content in the soil and the dry weight of rice grain was the highest for the soil which was treated with long bean plant material

unknown. Telah dilakukan tiga percobaan, yaitu percobaan inkubasi di laboratorium, percobaan pot di rumah kaca dan percobaan lapang yang dilakukan di KP Muara, Bogor. Tujuan penelitian ini adalah untuk mempelajari pengaruh berbagai jenis bahan tanaman kekacangan sebagai pupuk hijau terhadap kesuburan tanah dan produktivitas tanaman padi. Tanah Latosol dari KP Muara, Bogor digunakan dalam percobaan ini dan isotop 14C dipakai sebagai perunut dekomposisi bahan tanaman. Empat jenis bahan tanaman kacang panjang, kacang tunggak, kacang hijau, dan kacang gude yang dipanen pada umur 2 bulan setelah tanam, kecuali kacang gude 3,5 bulan (saat petik buah masak pertama) masing-masing dipersiapkan secara full tillage dan minimum tillage dipakai pada percobaan ini. Percobaan inkubasi dilaksanakan dengan metode penangkapan CO2 dalam suatu sistem yang tersusun dari 4 buah Erlenmeyers. Pada percobaan pot dan lapang, tanah yang telah memperoleh perlakuan tanaman kekacangan ditanami padi varietas Atomita IV. Parameter yang diamati pada percobaan inkubasi adalah persen- pembebasan 14C sebagai 14CO2. Pada percobaan pot yang diamati adalah kadar N-amonium, N-nitrat, dan N-mineral; kadar N-, P-, C-organik, dan K-total; serta bahan tanaman yang tidak melapuk dalam tanah. Untuk percobaan lapang yang diamati ialah produksi bobot kering gabah. Hasil percobaan inkubasi menunjukkan, bahwa laju pembebasan 14CO2 (persen 14C/hari) dari tanah yang diberi tiga jenis bahan tanaman kekacangan lainnya, yaitu 4 persen 14C/hari pada hari ke-2 inkubasi. Kadar unsur hara yang tertinggal dalam tanah dan produksi gabah kering dari tanaman yang diberi bahan tanaman kacang panjang secara nyata lebih tinggi daripada yang diberi tiga jenis tanaman kekacangan lainnya