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The only location for the protection of Arowana golden-red in its natural habitat is in east-central Sumatra. Currently, the area is being invaded by oil palm plantations. This research identified the present conditions in that conservation area, specifically focusing on land-use situation and aquatic organism distribution and diversity. We designated four sampling sites according to the stratification of river flows that pass through the Arowana golden-red conservation area and present land use. The research showed that oil palm plantation was the largest land use in the Arowana golden-red conservation area covering 61.2% (2,310.84 ha). The swamp forest which is the habitat of Arowana golden-red only remained at 6.99% (263.98 ha). In the study area, aquatic organisms were identified as 47 species with a total of 424 individuals: 7 genera of Benthos, 11 species of Planktonic algae, and 29 species of Fish. The diversity index was in the range of 0.46–2.45. The diversity of aquatic organisms was found to be comparable to or higher than other areas in Malaysia and Indonesia such as Aceh province and Kalimantan. However, only 31 individuals of Arowana golden-red were found in the swamp forest in Middle Mahato. This site should be a priority area to save the Arowana golden-red.

Rice husk biochar (RHB) is a potential source of available silicon in paddy soil and an ecologically responsive soil amendment for sustainable rice production. The study tested the influence of RHB application methods on rice growth, rice yield, and silicon dynamics in sandy loam soil in a pot experiment. RHB was applied at 5 tons ha−1 as a localized-spot-application (LSA) or top-mixed-application (TMA) with the soil at the upper 7 cm or whole-mixed-application (WMA) within 20 cm of the soil column and at 10 tons ha−1 in the TMA and WMA methods and was compared with a control (CTRL) without biochar. Seedlings of the Koshihikari rice variety were transplanted in each pot, and all treatments were replicated thrice. Compared to the CTRL, the LSA and TMA methods did not influence the mean porewater silicon concentration at the vegetative and reproductive stages. However, the WMA method applied at 5 tons ha−1 increased (p < 0.05) the mean porewater silicon concentration by 12.3 and 39.5% at the vegetative and reproductive stages, respectively, while at 10 tons ha−1, the respective increase was by 26.1 and 32.7%. All biochar application methods at the 5 tons ha−1 rate increased the rice grain yield (p < 0.05) by 21.2% (LSA), 11.3% (TMA), and 47.2% (WMA) compared to the CTRL. Conversely, at 10 tons ha−1, the yield was reduced by 18% in the TMA method, attributable to the immobilization of nitrogen and adsorption of nutrients to biochar surfaces. Our results proved that the choice of biochar application method and rate of application significantly influenced the dissolution of silicon in the porewater, leading to a higher silicon uptake and consequently a higher grain yield. This study provides valuable insights for agricultural practices aiming to enhance silicon dynamics in paddy soil and sustainable rice yield using RHB. [ABSTRACT FROM AUTHOR]

This study examined the influence of rice husk (RH) particle size, carbonization temperature, and their interaction on the availability of Silicon (Si) in RH biochar obtained from the carbonization of different particle sizes of RH (≤1 mm, >1 mm, and the original size, i.e., the unmodified RH biomass (O_RH)) at varying carbonization temperatures from 300 to 700°C. Silicon content in the biochar was extracted with 0.01 M CaCl2. Results showed that the influence of RH particle size on available Si is modified by temperature. The maximum available Si from the RH biochar were 2145 mg kg−1 at 700°C for O_RH, 2428 mg kg−1 at 600°C for > 1 mm RH and 2562 mg kg−1 at 500°C for ≤ 1 mm RH. These were an increase of 171%, 207% and 224% respectively, compared to the uncarbonized original rice husk (790 mg kg −1). Smaller particle sizes attained the maximum values of available silicon at lower temperatures compared with the original RH probably due to the efficient heat transfer to the smaller RH particle surface because of the smaller packing/void volume between the particles. Thus, the carbonization of smaller particles of RH will produce higher available Si content at a lower carbonization temperature than that required to achieve the same effect in the original RH biomass, thereby saving energy and time. [ABSTRACT FROM AUTHOR]

This study examined factors influencing the adoption of sawah technology in Kebbi State, Nigeria. Sawah refers to levelled rice field surrounded by banks with inlet and outlet for irrigation and drainage. Using pre-tested interview guide, data were collected from 300 sawah farmers in the study area. Data collected were analysed with both descriptive and inferential statistics using STATA package. The results showed that respondents were predominantly male, married and had no formal education. The mean age of was 48.13 years with mean household size of 14 persons; farm sizes ranged from 1–50 hectares with average of 4.70 ha, the mean yield was 6.88 tꞏha−1. The results further showed that bond construction had 100% adoption, nursery 99%, puddling 98%, flooding 95%, leveling and smoothening 94% and power tiller use 88% adoption. Adoption of sawah technology was influenced by socio economic characteristics which include sex, age, educational level, farm size, yield and income of the farmers. The study also showed that the attributes of sawah, production factors, information and extension and perception of respondent toward sawah technology influenced adoption. It is concluded that the sawah eco-technology is widely adopted by rice farmers in Kebbi State. The study therefore recommended that dissemination of sawah to other states in Nigeria need to consider factors that promote its adoption. Improvement of those factors that significantly affect adoption of sawah technology is also recommended.

The purpose of this study was to characterize and present the distribution of heavy metals especially Cd on agricultural and non-agricultural lands and river sediments in relation to soil erosion and topography status in watersheds. The study was conducted for a detailed soil survey by collecting 146 soil sample based on land use, soil family and topography position and 23 river sediments sample. The Cd was extracted by 0.1 M HCl and determined by ICP. The result showed that the concentration of Cd in soil and river sediment were low in toxicity based on FAO recommendation (Cd 0.4 mg/kg) with only 4 out of 169 sampling sites contained Cd exceeding the toxicity level. Volcanic ash from Mount Talang Volcano is a natural source of Cd in Sumani watershed. Cd concentration was low in areas with high soil erosion, which indicate material translocation caused by high soil erosion that accumulates sediment in plains and rivers. Agricultural soil was found to be low in soil pH and clay accompanied by high R factor and upland topography hence the increase in Cd concentration of the soil. The study concluded that Cd abundance in soils may be influenced by soil pH, texture, total carbon, erosion factors, and topography.