Oslan Jumadi

Mitigation options for N2O emission from a corn field in Kalimantan, Indonesia

Abstract Field experiments were designed to quantify N2O emissions from corn fields after the application of different types of nitrogen fertilizers. Plots were established in South Kalimantan, Indonesia, and given either urea (200 kg ha−1), urea (170 kg ha−1) + dicyandiamide ([DCD] 20 kg ha−1) or controlled-release fertilizer LP-30 (214 kg ha−1) prior to the plantation of corn seeds (variety BISI 2). Each fertilizer treatment was equivalent to 90 kg N ha−1. Plots without chemical N fertilizer were also prepared as a control. The field was designed to have three replicates for each treatment with a randomized block design. Nitrous oxide fluxes were measured at 4, 8, 12, 21, 31, 41, 51, 72 and 92 days after fertilizer application (DAFA). Total N2O emission was the highest from the urea plots, followed by the LP-30 plots. The emissions from the urea + DCD plots did not differ from those from the control plots. The N2O emission from the urea + DCD plots was approximately one thirtieth of that from the urea treatment. However, fertilizer type had no effect on grain yield. Thus, the use of urea + DCD is considered to be the best mitigation option among the tested fertilizer applications for N2O emission from corn fields in Kalimantan, Indonesia.

Production and Emission of Nitrous Oxide and Responsible Microorganisms in Upland Acid Soil in Indonesia

Incubation and field experiments were conducted to determine emission and production of nitrous oxide (N2O) and responsible microorganisms in an upland acid soil of Indonesia. The results showed that N2O productions in the soil samples were affected by ammonium and urea amendments compared with control. N2O production reached the highest peak at the first week then decreased until 4 weeks incubation in the potato and tea soil samples. However, more N2O production was found in tea soil than potato soil. Pine forest soil produced N2O more at second week incubation than first week, then decreased until 4 weeks. These results further confirmed that the N2O emitted in the field, which was higher in tea garden than other fields. The both ammonium and nitrate contents in the tea soil were higher than potato and pine soils. The number of ammonium oxidizers in the pine and potato soils was not significantly different, but it was lower in the tea soil. Number of nitrite oxidizers was almost the same in the potato and tea soils, however it was lower in the pine soil. The number of denitrifiers was 1–3 orders magnitude higher in the tea soil than the potato and pine soils.

Community Structure of Ammonia Oxidizing Bacteria and Their Potential to Produce Nitrous Oxide and Carbon Dioxide in Acid Tea Soils

The potentials of nitrous oxide (N 2 O) and carbon dioxide (CO 2 ) production in acid tea soils from Indonesia and Japan were investigated in a laboratory incubation experiment, and the community structures of ammonia-oxidizing bacteria in these soils were characterized using PCR-DGGE approaches. The soils used were sampled from tea plantations in Shizuoka, Japan and in Bogor and Malino, Indonesia. All of the soils were acidic (pH 3.45 to 4.00). The N 2 O and CO 2 production in Shizuoka was almost 5 times higher than in Bogor and Malino. All of the amoA gene sequences defined belong to the genus Nitrosospira sp. with cluster 2 and cluster 3a.

Influence of Azolla (Azolla microphylla Kaulf.) compost on biogenic gas production, inorganic nitrogen and growth of upland kangkong (Ipomoea aquatica Forsk.) in a silt loam soil

Abstract Azolla microphylla Kaulf. (Azolla) biomass was composted to create a high nitrogen (N) organic matter amendment (Azolla compost). We examined the effect of this Azolla compost on carbon (C) and N mineralization and the production of biogenic gases, nitrous oxide (N2O) and carbon dioxide (CO2), in a soil incubation experiment. A pot experiment with upland kangkong (Ipomoea aquatica Forsk.) examined plant growth in silt loam soil treated with three levels of Azolla compost. The results showed that N2O production from soil increased with urea amendment, but not with Azolla compost treatments. The Azolla-amended soil showed enhanced CO2 production throughout the 4-week incubation. The Azolla-treated soils showed a 98% lower global warming potential compared to urea treatment over the 4-week incubation. However, Azolla-amended soil had higher nitrate (NO3–) levels compared to urea-fertilized soil at 1 week of incubation, and these were maintained until the fourth week. Soils amended with Azolla compost showed lower ammonium nitrogen (NH4-N) levels than those in the urea-fertilized soils. The height and dry weight of upland kangkong fertilized with Azolla compost were similar to plants receiving urea fertilization. Therefore, the use of Azolla compost as a substitute for urea fertilizer would be beneficial for reducing the production of N2O while maintaining plant growth.