523 research outputs found
Nitrate Contamination of Groundwater and Soil Management
No full textThe Japanese Government set the environmental quality standard for nitrate (NO3) in groundwater at 10 mg N L1 in 1998, based on a level considered acceptable for avoiding infant methemoglobinemia. In 1998, 6.3% of groundwater in Japan contained NO3 exceeding 10 mg L¡¦, with agriculture regarded to be a primary source of the NO3 (Environmental Agency, Japan, 1999). This paper aims to define the mechanisms of NO3 contamination of groundwater associated with soil management in arable land.
The author gives an overview of the relation between nitrogen (N) fertilization and groundwater contamination. First of all, the utilization efficiency of N fertilizers for outdoor cultivation of vegetables is usually 50% or less (Nishio, 2001; Vance, 2001). Although N fertilizer is essential for crop production, excessive N could leach out of arable soils and eventually cause NO3 contamination of groundwater. However, conversely, excessive N is necessary as insurance in some cases, such as when there is heavy rainfall immediately after fertilization. It should be also noted that some vegetables physiologically require a high content of N in soil even at harvest.
Nitrate leaching from different fertilizers was monitored for 7 years and the data were evaluated using an N and water balance equation (Maeda et al., 2003). Excessive N from chemical fertilizers caused substantial NO3 leaching, while compost application was promising to achieve high yields and low N leaching during a few years but led to the same level of NO3 leaching as that in the plots subjected to chemical fertilizer application over longer periods of time. Thus, it is of importance to predict the N mineralization rates both for manure and for soil under natural conditions. Experimental results of this kind can provide full information on N dynamics in fields for policy decisions or regulations to reduce NO3 leaching while maintaining crop yields. Likewise, we must consider other influencing factors such as soil types, climatic conditions, and cropping systems for this purpose
ノウコウチ ニ オケル ショウサンセイ チッソ ニ ヨル チカスイ オセン ノ ボウシ ニ カンスル ケンキュウ
No full text京都大学0048新制・論文博士博士(工学)乙第11033号論工博第3684号新制||工||1252(附属図書館)UT51-2003-B395(主査)教授 西牧 研壯, 教授 森澤 眞輔, 教授 津野 洋学位規則第4条第2項該当Doctor of EngineeringKyoto UniversityDFA
NITRATE LEACHING UNDER INTENSIVE FARMING AND SUCH INFLUENCING FACTORS AS TYPE OF FERTILIZER AND SOIL
No full textJoint Research on Environmental Science and Technology for the Eart
A STUDY ON PHYSICO-CHEMICAL CHARACTERISTICS OF SEMI-INTENSIVE SHRIMP POND SEDIMENT
No full textWater quality management has been considered one of the most important factors in aquaculture techniques, but less pay attention in pond bottom soil quality management (Boyd 2002). Poor sediment conditions may cause low survival and poor production of shrimp aquaculture. It is therefore important to investigate physicochemical characteristics of aquaculture pond sediments. Sediment samples were taken randomly from five semi-intensive aquaculture ponds in the Tam Giang Lagoon in Sep. 2010 (dry season) and March 2011 (wet season) by using a 5–cm diameter core sampler, which was designed to trap a layer of soil 0–2 cm, 2–6 cm and 6–10 cm depth from the pond bottom interface. The results indicated that there was a significant difference between sediment layers for nutrient elements: total carbon (TC); total nitrogen (TN), C: N ratio, total phosphorus (TP), mineral composition (p<0.05). But there was not found significant difference in δ15N between sediment layers and shrimp culture cycle seasons (p>0.05). Keywords: Aquaculture, mineral composition, nutrient elements, physico-chemical, soil layer.</jats:p
Development of environment-friendly aquaculture technologies and practices
No full textThe significant role of aquaculture in providing food security has been recognized, not only through its contribution to food supply, but also through the promotion of economic and social well-being. Aquaculture is also considered as a relatively recent and underdeveloped sector as compared to agriculture and animal husbandry, and there is a huge, unfulfilled potential in many countries, particularly in the region. The recently concluded ASEAN-SEAFDEC Conference “Fish for the People” highlighted the importance of sustainable fisheries for regional food security, and the need for comprehensive and cooperative efforts, resolutions and plan of actions among all stakeholders. With the projected shortfall in the supply of fish and fishery products to meet the demands of an ever-increasing population, aquaculture is looked upon as a sustainable source of renewable food resources.
One of the main programs of the SEAFDEC Aquaculture Department (AQD) is geared towards the development of sustainable aquaculture that is technically feasible, economically viable, environment-friendly, and socially equitable. An important subprogram is the development of environment-friendly aquaculture technologies and practices. The objectives of the subprogram are: 1) to develop and promote efficient aquaculture systems and designs for maximum sustainable productivity; 2) to devise and determine appropriate design, equipment, and operation and management practices that optimize utilization of resources and inputs, minimize adverse impacts on the environment, and sustain biological/ecological diversity; 3) to demonstrate, verify, adopt, refine, and promote proven aquaculture technologies and practices; and 4) to advance the social, economic, cultural, and policy importance of the aquaculture sector at the local, national, and regional level. At present, the main research areas are in nutrient dynamics of aquaculture systems, feed and waste management, development of culture systems, including bioremediation strategies, conservation and sustainable utilization of resources for aquaculture, and socio-economic and policy issues in aquaculture. In addition, verification and refinement of developed aquaculture technologies, in support of re search and training activities, are conducted to explore the potential of aquaculture technologies for commercial adoption and demonstrate appropriate technologies and responsible aquaculture practices. The paper presents an overview of current research activities by the author, and with involvement of other researchers at SEAFDEC AQD, including future plans under this and related programs
Nutrient Mass Balances in Intensive Shrimp Ponds with a Sludge Removal Regime: A Case Study in the Tam Giang Lagoon, Central Vietnam
No full textUnderstanding the sources and sinks of nutrients is of significant importance for better management of pond water quality and the environmental impact of aquaculture. The objective of the present study was to estimate the nutrient mass balances of four intensive shrimp (Litopenaeus vannamei) ponds in Tam Giang Lagoon, Central Vietnam, using a sludge management regime. The nutrient budgets were calculated based on the sources and sinks of nutrients in the ponds over a period of 49 d. The input sources of N and P were mainly shrimp feed, which accounted for more than 90%. Shrimp harvesting was the largest sink of N (37.5%), but not of P (18.3%). Almost a 30.4% N and 16.9% P of input were not accounted for the measured losses. While the smallest proportion of N (18.9%) was retained in sludge, the largest amount of P was accumulated in sludge (53.2%). The farm was operated without water exchange, so ponds gained only 1.9% N and 4.2% P from water intake. The pond lost about 13.2% N and 11.6% P from discharge water. Production of 1 kg shrimp needed 84.9 g N and 26.1 g P from total input sources and discharged 47.3 g N and 16.0 g P to the environment. Environmental losses of nutrients were lower or intermediate, when the loads were expressed in both kg/ha/cycle and kg of N or P per ton of shrimp produced. Furthermore, the environmental impacts of aquaculture are controlled from the system. Key words: Shrimp pond, L. vannamei, nutrient mass balances, N, P.
« Parsadan Gorgijanidze’s Exile in Shushtar: A Biographical Episode of a Georgian Official in the Service of the Safavids ». Journal of Persianate Studies 1, 2, 2008, p. 218-229.
No full textAt the beginning of the article, Maeda states his opinion that many Safavid ġolāms were far from severing all ties with their homeland: here the Author agrees with the views of other modern Safavid scholars but he (rightly, in the opinion of the present reviewer) contradicts what one often reads in the scholarly literature concerning military slavery in the Muslim world in general. Maeda is also correct in stating that “by introducing the institution of the royal ġolāms, the Safavids imported..
Leaching patterns of heavy metals and nitrogen evaluated with a modified tanks-in-series model
No full textÁP DỤNG MÔ HÌNH LANGMUIR ĐỂ XÁC ĐỊNH KHẢ NĂNG HẤP PHỤ PHỐT PHO CỦA TRẦM TÍCH ĐÁY AO NUÔI TÔM BÁN THÂM CANH
No full textPhốt pho (P) là yếu tố quan trọng gây ra hiện tượng phú dưỡng tại các khu vực cửa sông và ven biển, nơi tập trung nhiều chất thải có hàm lượng dinh dưỡng cao. Nguồn P được đưa vào trong hệ thống nuôi trồng thủy sản từ bón phân cải tạo ao, thức ăn dư thừa, chất thải và xác chết của sinh vật. Kết quả nghiên cứu của nhiều tác giả cho thấy hàm lượng phốt pho trong nước phụ thuộc vào đặc tính trao đổi giữa tầng nước và chất đáy. Phốt pho có thể bị giải phóng hoặc hấp phụ vào nền đáy ở môi trường nhất định nào đó. Mô hình để mô phỏng sự hấp phụ phốt pho có thể dự đoán lượng chất bị hấp phụ rất có ích cho việc quản lý chất lượng môi trường nước ao nuôi trồng thủy sản và sự phú dưỡng của đầm phá Tam Giang do có nhiều nước thải trực tiếp chưa được xử lý từ các hệ thống nuôi tôm. Nghiên cứu này được tiến hành để kiểm tra động lực hấp phụ và khả năng hấp phụ P của trầm tích đáy ao nuôi tôm bán thâm canh ở môi trường được điều chỉnh ở mức pH và hàm lượng P đưa vào khác nhau. Kết quả nghiên cứu cho thấy lượng P bị hấp phụ trong trầm tích đáy ao ở các mức pH thay đổi từ 5 - 8,5 là tương đối thấp. Điều này được cho là do tỷ lệ cát quá cao trong mẫu trầm tích (> 60 %) dẫn tới diện tích bề mặt hấp phụ thấp và các vị trí hấp phụ hoạt động kém. Động lực hấp phụ P tăng nhanh ở trong 10 phút đầu và đạt giá trị cân bằng tại thời điểm 1h của thí nghiệm ở nồng độ P = 0,5 mg/L, còn với nồng độ P ban đầu là 5 mg/L thì động lực hấp phụ tăng nhanh ở 30 phút đầu tiên và đạt cân bằng ở thời điểm 2,5h. Mô hình Langmuir có hệ số tương quan (R2 = 0,952 – 0,996) mô tả tương đối chính xác quá trình hấp phụ P của trầm tích đáy ao và khả năng hấp phụ cực đại (Г max) của đáy ao đã xác định được ở pH 5; 7 và 8,5 lần lượt là 0,29; 0,27; 0,27 mg/g. Từ khóa: Hấp phụ, Nuôi trồng thủy sản, Mô hình Langmuir, Phốt pho, Trầm tích.</jats:p
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