Erry Purnomo

Seasonal changes of CO2, CH4 and N2O fluxes in relation to land-use change in tropical peatlands located in coastal area of South Kalimantan

Tropical peatland could be a source of greenhouse gases emission because it contains large amounts of soil carbon and nitrogen. However these emissions are strongly influenced by soil moisture conditions. Tropical climate is characterized typically by wet and dry seasons. Seasonal changes in the emission of carbon dioxide (CO(2)), methane (CH(4)) and nitrous oxide (N(2)O) were investigated over a year at three sites (secondary forest, paddy field and upland field) in the tropical peatland in South Kalimantan, Indonesia. The amount of these gases emitted from the fields varied widely according to the seasonal pattern of precipitation, especially methane emission rates were positively correlated with precipitation. Converting from secondary forest peatland to paddy field tended to increase annual emissions of CO(2) and CH(4) to the atmosphere (from 1.2 to 1.5 kg CO(2)-C m(-2)y(-1) and from 1.2 to 1.9 g CH(4)-C m(-2)y(-1)), while changing land-use from secondary forest to upland tended to decrease these gases emissions (from 1.2 to 1.0 kg CO(2)-C m(-2)y(-1) and from 1.2 to 0.6 g CH(4)-C m(-2)y(-1)), but no clear trend was observed for N(2)O which kept negative value as annual rates at three sites.

Greenhouse gas emissions from tropical peatlands of Kalimantan,Indonesia

Greenhouse gas emissions were measured from tropical peatlands of Kalimantan, Indonesia. The effect of hydrological zone and land-use on the emission of N2O, CH4 and CO2 were examined. Temporal and annual N2O, CH4 and CO2 were then measured. The results showed that the emissions of these gases were strongly affected by land-use and hydrological zone. The emissions exhibited seasonal changes. Annual emission of N2O was the highest (nearly 1.4 g N m−2y−1) from site A-1 (secondary forest), while there was no signi.cant difference in annual N2O emission from site A-2 (paddy field) and site A-3 (rice-soybean rotation field). Multiplying the areas of forest and non-forest in Kalimantan with the emission of N2O from corresponding land-uses, the annual N2O emissions from peat forest and peat non-forest of Kalimantan were estimated as 0.046 and 0.004 Tg N y−1, respectively. The emissions of CH4 from paddy field and non-paddy field were estimated similarly as 0.14 and 0.21 Tg C y−1, respectively. Total annual CO2 emission was estimated to be 182 Tg C y−1. Peatlands of Kalimantan, Indonesia, contributed less than 0.3 of the total global N2O, CO2 or CH4 emission, indicating that the gaseous losses of soil N and C from the study area to the atmosphere were small.

Effect of land-use changes on nitrous oxide (N2O) emission from tropical peatlands

Tropical peatlands could be a potential source of nitrous oxide (N2O) which has a significant impact on global warming. To reduce N2O emission and develop best management practices for peatlands, the formation and emission rates of N2O as affected by land-use management (i.e., changing peatland into agricultural land) and the factors affecting the process must be understood. Therefore, one field and three laboratory incubation experiments were carried out during 1998–99 using peatland soils from 12 sites in South Kalimantan (Indonesia) and one site in Sarawak (Malaysia) to quantify the N2O emission and the factors affecting it. The results from the field experiment showed that land-use managements, changing water table and locations had a significant impact on N2O emission. Changing peatland into cultivated lands (cultivated upland and paddy field) enhanced the N2O emission. For example, cultivated upland Cassava crop resulted in the highest amounts of N2O emission (1.04 mg N m−2 h−1) compared to other treatments. The N2O emission during 1998 was higher than those during 1999 because of the changing water table and dry season in 1998. The laboratory experiments showed that the N2O emission was also strongly influenced by land-use management, soil moisture contents, addition of ammonium fertilizer or rice straw and soil depths. For example, the flooded conditions stimulated the N2O emission compared to that at 60% moisture contents. Similarly, the addition of ammonium fertilizer suppressed the N2O emission compared to control treatments because of the high ammonium contents that inhibit nitrification. Nevertheless, incorporation of rice straw to soil samples from 20 to 40 cm soil depth stimulated N2O emission.

Phosphorus Solubilizing Microorganisms in the Rhizosphere of Local Rice Varieties Grown without Fertilizer on Acid Sulfate Soils

Local farmers who living in South Kalimantan (Banjarese farmers) apply almost none of phosphatic (P) fertilizers to grow local rice varieties. This practice has been adopted for many years. We have investigated the mechanisms involved in P availability for the crop. This study focuses on identifying microorganisms involved in solubilizing insoluble P. The study was conducted in Balandean District, South Kalimantan, Indonesia. The soil was classified as acid sulfate soil. Three out of 8 rice varieties grown were selected for net P balance in the soil-plant system and the microbial studies. We found that the P uptakes by the rice crop was much higher than the sum of P released from soil, water and soil microbial biomass P. It was also observed that these soils harboured bacteria and fungi that have the capability of dissolving aluminium phosphate (AIPO4) and tricalcium phosphate [Ca3(PO4)2]. Based on the area of clear zone on plates, it seem that there were variations of ability in dissolving Al-P or Ca-P. DNA sequence analysis shown that Burkholderia sp. was the common P solubilizing bacterium found in the rhizosphere of rice varieties Siam Unus, Siam Ubi and Siam Puntal. The presence of other bacteria was specific for each rice variety grown.

Design of Sphingomonad-Detecting Probes for a DNA Array, and Its Application to Investigate the Behavior, Distribution, and Source of Rhizospherous Sphingomonas and Other Sphingomonads Inhabiting an Acid Sulfate Soil Paddock in Kalimantan, Indonesia

Throughout Central and South Kalimantan, Indonesia, strongly acidic soil (pH 2.1–3.7) is widely distributed, and the local acidic soil-tolerant plants, including local rice varieties, often possess sphingomonads in their rhizosphere and rhizoplane. To investigate the behavior of sphingomonads inhabiting the rhizosphere of such acid-tolerant plants, we designed 13 different DNA array probes (each of 72 mer) specific to a group of sphingomonads, using a hypervariable V6 region of the 16S rRNA gene. This DNA array system was used preliminarily for an analysis of microfloral dynamisms, particularly of sphingomonads, in acidic paddock ecosystems, and the results suggest that the acid-tolerant local rice shares rhizospherous sphingomonads with wild Juncus sp., a predominant weed that thrives in acidic paddocks during the off-season for rice farming. This tentative conclusion supports the bio-rationality of the traditional rice farming system with respect to functional rhizobacteria.

Extreme High Yield of Tropical Rice Grown Without Fertilizer on Acid Sulfate Soil in South Kalimantan, Indonesia

Land Characteristics of Batang Pelepat Watershed In Bungo District, Jambi (Sunarti): Land characteristics describe biophysics characteristics of watershed. But, land has been used for economic oriented. The objective of this research is to identify land characteristics of Batang Pelepat watershed. Data collection was carried out by survey based on land unit map and analyzed by descriptive analysis. The results showed that land in Batang Pelepat watershed consist of 23 land units and some land use types (forest, rubber and oil palm farming, settlement and shrub), soil parent materials variously (alluvium, granite, tuff andesite, basalt, and clay rock), soil depth ranges from 88 to 160 cm and soil texture is classified moderate fine to fine. Lands were dominated by slope of >15–30% and >45–65% and dystrudepts of soil group with soil fertility level very low to low because its pH about 3.80-6.20, base saturation about 7.86-32.79% and P- available about 2.80-25.00 ppm. Various land use has also caused different erosion and permeability levels.