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2017-08-30T02:06:39

In aquaculture systems, insufficient nutrients impede shrimp growth while excessive amounts of nutrient inputs lead to environmental degradation and unnecessary high investment. A study of in-out nutrient budgets in an intensive Litopenaeus vannamei farm was conducted in this work to measure the amount of nitrogen (N) and phosphorus (P) input and output from the system. The feed conversion ratio (FCR) was obtained to determine the level of nutrient input performance. Between September and December 2017, monthly water and sediment samples were taken within one crop cycle. Nutrient concentrations in sediment and water increased over 90 days. The total nitrogen concentration in the pond water and effluents were in accordance with wastewater quality control for aquaculture; however, the total phosphorus concentration failed to meet the water quality control from the water input through the end of the crop cycle. The nutrient budget model showed that the input/output contained 107.8 kg N and 178.4 kg P. Most of the N input came from shrimp diets (80%) while most of the P came from fertilizer (57%). Both N (46%) and P (54%) mainly deposited in the sediment as an output process. The FCR of this farm is 2.0. Based on the 1.8 FCR scenario, this farm could reduce 147 kg of feed in total, which accounts for 9.04 kg N and 2.21 kg P reduction. The farmer could save $1027 USD crop − 1 ($1 USD = 32.7 baht), as well as reducing uneaten food at the bottom of the pond. This study offers a simple and straightforward model that can practically reduce environmental impacts and increase the profitability of farms.

Degradation and destruction of mangrove forests in many regions have resulted in the alteration of carbon cycling. Objectives of this study were established to answer the question regarding how much soil organic carbon (SOC) is stored in wetland soils in part of the upper northeastern Gulf of Thailand and to what extent SOC is related to organic matter (OM). A total of 29 soil samples were collected in October 2015. Soil physiochemical analyses followed the standard protocol. Spatial distributions were estimated by a kriging method. Linear regression and coefficient were used to determine the suitable conversion factor for mangrove soils. The results showed that surface soil (0-5 cm) contained higher SOC content as compared to subsurface soil (5-10 cm). Considering a depth of 10 cm, this area had a high potential to sequester carbon with a mean ± standard deviation of 5.59 ± 2.24%. The spatial variability of OM and SOC revealed that organic matter and carbon decreased with the distance from upstream areas toward the gulf. Based on the assumption that OM is 50% SOC, the conversion factor of 2 is recommended for more accuracy rather than the conventional factor of 1.724.

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The soil bacterial community is critical for understanding biological processes in soils and is used for agricultural soil management. The understanding of microorganisms and ecology in different soil groups classified based on soil properties (e.g., minerals, soil texture, location, nitrogen, phosphorus, organic carbon and pH, among others), is limited. To suggest soil management strategies using bacterial data, we classified soils into four groups based on physical–chemical characteristics and elucidated their relationships with soil nutrient characteristics and the bacterial community in agricultural fields in Saraburi Province, Thailand. Results show that soil groups with high bacterial diversity had positive correlations with total Kjeldahl nitrogen and available phosphorus but were negatively affected by total organic carbon and pH levels. Dominant bacterial genera included Lactobacillus, Phascolarctobacterium, Prevotella, Clostridium, Gaiellales and Blautia. Significant key biomarkers were found (p < 0.05). Nutrient-rich soil groups (high available P, acidic pH) were found with genus Agromyces, while low nutrient soil groups (low available P, basic pH) were found with Hydrogenispora, Ignavibacterium and Bauldia. Based on co-occurrence networks, organic degrading bacteria functioned with other bacteria at high degrees of interconnections, suggesting organic amendment, biostimulation and biodegradation using nutrient-rich organic substrates could be used for agricultural soil improvements.

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Khaya ivorensis (K. ivorensis), one of the most valuable tropical hardwood species indigenous to West and Central Africa, has been classified as a threatened tree species. However, information on its remaining population and distribution are limited. We mapped the current K. ivorensis spatial distribution, modelled the spatial autocorrelation and estimated its economic value using volume estimation and market pricing. The study was conducted in Odigbo and Irele local government areas (LGA), Ondo State, Nigeria. Spatially, localities of 97 K. ivorensis were identified across the study area and can be added into a wide range of datasets from local to global inventories. Large trees in diameter and height were statistically clustered in the north of Odigbo and assumed to relate with forest reserve management. Estimated median tree volumes were 0.39 m 3 and 0.31 m 3 in accordance with the allometric volume function and specific volume function, respectively. The economic values of wood varied approximately from US$111,208 to US$72,081. Findings from this study are a valuable resource for conserving this species and other threatened tree species. Recent international agreements under Sustainable Development Goal 15 (Target 15.5 of the UN Climate Summit 2014) and the New York Declaration on Forests take ambitious goals to at least halve the rate of loss of natural forests globally by 2020 and take action to end natural forest loss by 2030, as well as protect and prevent the extinction of threatened species 1,2. Khaya ivorensis (K. ivorensis), one of five species of African mahogany commonly found in coastal West Africa, Cote d'Ivoire through Ghana, and southern Nigeria to Cameroon, has been listed on the World Conservation Union (IUCN) Red List of Threatened Species since 1998 3. With respect to IUCN criteria, this species meets the critical value for a threat status of A1 as 'vulnerable' and A2 as 'near extinct'. K. ivorensis declined by 48% between 2005 and 2015 and is anticipated to reach 432% reduction in the next decade 4. While K. ivorensis remains an important tree species, it is widely sought after in international timber markets and used for a wide range of consumption such as veneer, interior joinery, exterior joinery, boat building, and medicinal purposes 5. It is generally agreed that timber from man-made forests have lower yield and inferior wood quality compared to those from natural forests 6. Mahogany plantation is no exception. High exploitation rates, combined with little or no regeneration after disturbance, has led K. ivorensis to become an endangered tree species. Furthermore, the plantation establishment of this species has been largely unsuccessful because of shoot borer Hypsipyla robusta Moore attack 7. The shoot borer of these pest species destroys the leading shoot, resulting in poor form, and severe loss from stunted growth, which affect the quality and economic value of the timber 8,9. The Global Forest Watch, University of Maryland, and World Resources Institute point out that of the ten co...