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分析了节水灌溉现状;以玉米苗期为研究对象,结合黑龙江省旱作农业实际,提出了一种与中耕相结合的灌溉方式,为采用机械化灌溉方法解决作物苗期干旱问题提供参考。 相似文献
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Carlos A Martínez-Palacios Maria Gisela Ríos-Durán Jorge Fonseca Madrigal Mayra Toledo Cuevas Angela Sotelo López & Lindsay G Ross 《Aquaculture Research》2008,39(7):738-747
The Mexican silverside, Menidia estor, is a species with great regional importance and with very high prices in local markets. Unfortunately, due to high fisheries pressure, environmental degradation and pollution, the species has become endangered. Recently, there has been much progress in the biotechnology of this species, aimed at its culture, and the present paper describes the advances in feeding and nutrition of those important fish. M. estor is a stomachless, zooplantophagous fish, which also occasionally feeds on small fish and crustaceans in the adult stage. Studies on the digestive enzymatic activities show high proteolytic capacity and a late or different model of digestive maturation from that described for marine stomach fish. Nutritional studies on M. estor have shown that juveniles have dietary requirements of about 400 g kg?1 protein and 80 mg kg?1 vitamin C. The upper level of dietary carbohydrate for good growth and survival for juveniles is about 150 g kg?1. Based on the high docosahexaenoic acid (DHA) content in flesh when fed on diets low in DHA, it is believed that the species has the capacity to biosynthetize >20‐carbon fatty acids from 18‐carbon fatty acids. The high levels of DHA in flesh makes this fish a very significant potential component of human nutrition. Using these findings the first practical diets for commercial culture of the species have been developed. 相似文献
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Effects of different dietary protein and lipid levels on growth, feed utilization and body composition of red porgy (Pagrus pagrus) fingerlings 总被引:1,自引:0,他引:1
D. SCHUCHARDT J.M. VERGARA H. FERNÁNDEZ-PALACIOS C.T. KALINOWSKI C.M. HERNÁNDEZ-CRUZ M.S. IZQUIERDO & L. ROBAINA 《Aquaculture Nutrition》2008,14(1):1-9
Two feeding trials were conducted to determine the minimum dietary protein level producing maximum growth, and the optimum protein to energy ratio in diets for red porgy (Pagrus pagrus) fingerlings, respectively. In the first trial, six isoenergetic diets were formulated with protein levels ranging from 400 to 650 g kg?1 in increments of 50 g kg?1, and fed for 11 weeks to 2.8 g average initial weight fish. Weight gain, specific growth rate and feed efficiency were significantly higher with diets containing higher protein levels, when compared with dietary levels below 500 g kg?1. The highest protein efficiency ratios were obtained in fish fed 500 g kg?1 dietary protein. The minimum dietary protein level producing maximum fish growth was found to be 500 g kg?1. In the second trial, 15 g average initial weight fish were fed for 12 weeks, six diets containing three different lipid levels (100, 150 and 200 g kg?1) combined with two protein levels (450 and 500 g kg?1). Weight gain values increased when dietary lipids increased from 100 to 150 g kg?1, with a further decrease for 200 g kg?1 lipids in diets; the lowest fish growth being supported by 200 g kg?1 dietary lipids. Fish growth was significantly higher when dietary protein increased from 450 to 500 g kg?1. There was no evidence of a protein‐sparing effect of dietary lipids. Liver protein and lipid contents were low when compared with other fish species. All diet assayed produced high liver glycogen accumulation. The recommended protein and lipid levels in diets for red porgy fingerlings were 500 and 150 g kg?1, respectively. 相似文献
5.
Irrigation scheduling strategies for cotton to cope with water scarcity in the Fergana Valley, Central Asia 总被引:3,自引:0,他引:3
The Central Asian countries face high water scarcity due to aridity and desertification but excess water is often applied to the main irrigated crops. This over-irrigation contributes to aggravate water scarcity problems. Improved water saving irrigation is therefore required, mainly through appropriate irrigation scheduling. To provide for it, after being previously calibrated and validated for cotton in the Fergana region, the irrigation scheduling simulation model ISAREG was explored to simulate improved irrigation scheduling alternatives. Results show that using the present irrigation scheduling a large part of the applied water, averaging 20%, percolates out of the root zone. Several irrigation strategies were analyzed, including full irrigation and various levels of deficit irrigation. The analysis focused a three-year period when experiments for calibration and validation of the model were carried out, and a longer period of 33 years that provided for an analysis considering the probabilities of the demand for irrigation water. The first concerned a wet period while the second includes a variety of climatic demand conditions that provided for analyzing alternative schedules for average, high and very high climatic demand. Results have shown the importance of the groundwater contribution, mainly when deficit irrigation is applied. Analyzing several deficit irrigation strategies through the respective potential water saving, relative yield losses, water productivity and economic water productivity, it could be concluded that relative mild deficits may be adopted. Contrarily, the adoption of high water deficit that produce high water savings would lead to yield losses that may be economically not acceptable. 相似文献
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为了进一步提高图书馆的信息服务水平,对河北农业大学读者信息需求进行了研究,显示出信息需求强烈、获取方法简捷、多层次化、载体类型多样化等特点,并提出了加强文献资源建设,合理配置资源;改进服务质量,提高服务水平;重视读者教育与培训工作;加强馆员培训,提高馆员综合素质等措施。 相似文献
8.
生态功能区建设对大兴安岭地区经济社会发展将产生重大影响,而摆脱生态功能区发展的科技瓶颈则是生态功能区建设成功的关键。为此,文章从大兴安岭地区生态功能区建设的科技需求入手,通过分析影响生态功能区发展主要科技问题,有针对性地提出支持大兴安岭生态功能区发展的科技对策,为大兴安岭地区制定生态功能区发展政策提供理论支持。 相似文献
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Summary Serum chloramphenicol concentrations were determined by microbiological and chemical assay methods in cows, ewes, and goats treated parenterally with seven different veterinary parenteral chloramphenicol products, including the water soluble sodium succinate ester of chloramphenicol and solutions of 20%, 25% and 50% of chloramphenicol base in various organic solvents. Serum drug concentrations were analyzed for the effect of product formulation differences, dosage, whether the drug was administered i.m. at a single body site or to two sites, and the method of assay, on the absorption from the injection site, peak drug levels, and the persistence in serum of effective concentrations of the drug i.e. 5 to 10 ug / ml. Although differences were observed among the 6 products containing chloramphenicol base in respect to absorption rate and peak serum drug levels, and although these differences significantly influenced the persistence of microbiologically‐active serum drug concentrations at the level of ≥ 10 μg / ml, they did not at the level of ≥ 5 μg / ml. In the animal species examined, injections given at 2 sites appeared to influence the duration of predetermined serum drug levels more than the differences among the products in respect of the absorption and elimination rates from serum, the peak serum concentrations, and the dose. The shapes of the concentration‐to‐time curves in cows and ewes injected with the same dose of a given product were essentially the same, but they were different in goats. Serum chloramphenicol concentrations measured chemically after treatment with chloramphenicol base were 20% to 46% higher than those measured microbiologically. For 60 minutes after the sodium succinate ester had been administered i.v. and i.m. to ewes, the chemically determined chloramphenicol levels were more than twice as high as the respective concentrations determined by microbiological assay, but thereafter, the magnitude of those differences was not greater than observed after treatment with chloramphenicol base. Intramuscular bioavailability of the products containing chloramphenicol base injected at 2 sites was rather poor (51% to 80.5%ofthe dose) and even lower values were calculated after injection at a single site. Results are briefly discussed of the effect of dosage form on the persistence of microbiologically effective serum drug levels. A dose of at least 50 mg / kg to be administered i.m. at two sites are essential prerequisits for chloramphenicol therapy in ruminants. 相似文献
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