Saidy AR, Mariana ZT, Adji FA, Nusantara RW, Fitria I, Syahrinudin. 2018. Carbon mineralization dynamics of tropicalpeats in relation to peat characteristics. Biodiversitas 19: 1413-1421. Understanding the dynamics of carbon mineralization of peats inthe tropical areas is of essential significance in controlling carbon dioxide (CO2) gas emission rates. An incubation study of tropicalpeats sampled from 3 different sites of the Barito Basin on the Borneo Island, Indonesia (uncultivated, used for paddy cultivation for  5years and 5-10 years) was carried out to investigate a relationship between CO2 production and peat characteristics. Results of studyrevealed that land use change from uncultivated peats to paddy fields resulted in significant changes in the chemical structure of peatorganic carbon. Carbohydrate contents of the peat decreased significantly as a consequence of the conversion of natural peats to paddyfields. However, the paddy peats contained higher lignin than uncultivated peats. Changes in the chemical structure of the tropical peatsresulted in changes in carbon mineralization. Carbon mineralization of uncultivated peats ranged from 29255310 mg CO2-C kg-1 peat,while carbon mineralization of 10652678 mg CO2-C kg-1 C peat was observed for paddy peats. Moreover, carbon mineralization dataobtained from the experiment fitted properly to a two-pool C mineralization model. The developed carbon mineralization model showedthat slowly and rapidly decomposable pools have a close relation with rubbed fiber and carbohydrate content data. Thus, results of thisstudy suggested that carbon mineralization of peats could be estimated appropriately using rubbed fiber and carbohydrate content data.

<div><p>Development of organic farming in tidal land should be wise and considers all aspects supporting the development of sustainable agriculture. The aim of this research was to quantify concentration of metals contained in tidal swamp water both at the single and double tides of various tidal typologies, including Pb, Cd, Cr, and Fe ions. The research was conducted in four villages in Barito Kuala regency (South Kalimantan) to represent tidal land types A, B, C and D, respectively. Sampling was carried out at spring and neap tides in each villages and the Barito river nearest to the villages. The water samples were collected in plastic bottles in the irrigation canals and brought to the laboratory for analysis of Pb, Cd, Cr and Fe concentrations.  The results showed that the Pb, Cd, Cr and Fe concentrations in studied area were &lt;0.002 - 0.0122 ppm, 0.0067 - 0.0122 ppm, &lt;0.002 - 0.0064 ppm and 0.0358 ppm - 9.0807 ppm for Pb, Cd, Cr and Fe, respectively. Based on he limiting factor in heavy metals of water quality for agricultural crops in land C and D type are cadmium (Cd) and iron (Fe) elements. Acidity of water on the land types C (pH 2.72 - 2.95) and D (pH 2.68 - 4.41) were lower than those in the land types A (pH 6.01 - 6.83) and B (pH 3.6 - 6.29).</p></div>

Aims: To optimize the dose of three ameliorants (biochar, lime, and compost) and their interactions on the availability of macronutrient P. Study Design: This research was a laboratory incubation study using soil samples from the newly opened rice fields. Place and Duration of Study: Paddy field of Ray 7, Balandean Village, Alalak District, Barito Kuala Regency, South Kalimantan Province from May to November 2021. Methodology: The study used factorial design with the treatments of 1) Biochar, with levels of 0, 10, and 20 t ha-1, 2) Lime, with levels of 0, 2, and 4 t ha-1, 3) Compost with levels of 0, 5, and         10 t ha-1. All were arranged in Completely Randomized Design with three replications. The experimental units were 300 g of soil sample in 81 of 10 cm plastic pots. They immersed up to 2 cm water and incubated to imitated field conditions for three months and then analyzed for the parameters. Results: Biochar and lime increased available-P quadratically and linearly following orthogonal polynomial analyses. Their interaction was highly significant in increasing available-P. The doses for both could be increased for the maximum availability of P. Conclusion: Biochar increased P availability with the tendency of increasing beyond the dose of the treatment. The main treatment of compost was not as good as biochar. However, when applied together with biochar and lime, compost affected the solubility of P. However, to increase P availability, the combination of the ameliorants showed a good synergism.