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121.
The Cu Chi irrigation system in Vietnam forms part of the Dau Tieng reservoir system in the Dong Nai basin. Water competition in this system is intensifying as a result of increasing urban and environmental demand. System operation modelling using the Irrigation Main System OPeration (IMSOP) model was applied to the Cu Chi irrigation system, Vietnam, to improve its operational performance. The operation improvement process involved the comparison of supply and demand during two years, 2001 and 2002, revealing that the system's operation was carried out without consideration of the crop water demand and proper canal regulation. The retrospective operational analysis revealed a substantial amount of oversupply and inequity of distribution. Two new operation strategies were selected after a simulation analysis and evaluated in the field. The new scenarios showed a more equitable distribution of water in the system. The average pre‐intervention supply–demand ratio which ranged from 1.68 to 2.51 was reduced to 1.20 for continuous flow and 1.17 for rotational operation. A comprehensive analysis of water reallocation to Ho Chi Minh City for urban and industrial purposes and its effect on the security of supply on the Cu Chi system was also undertaken. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
122.
以叶用栽培的宜昌红荷芋头球茎为材料,进行了不同球茎大小繁殖系数、球茎切块防腐烂处理、不同切块大小发芽和田间长势比较试验。结果表明,用草木灰或高锰酸钾处理可将球茎切块腐烂率控制在1.3%以下,不同大小切块繁殖出的水芋植株长势没有显著差异。 相似文献
123.
BP网络、Hopfield网络在水质评价应用中的比较研究 总被引：1，自引：0，他引：1
针对BP网络、Hopfield网络在水质评价的应用问题,建立BP网络、Hopfield网络水质评价模型,对BP网络、Hopfield网络从结构、输入输出、稳定性、评价结果等方面进一步地分析比较。然后以东辽河为例,运用BP网络、Hopfield网络、模糊评价法、内梅罗指数法4种水质评价方法进行水质评价,通过比较评价结果进行深入研究。结果表明,Hopfield神经网络更适用于水质评价。对神经网络方法水质评价问题进行探讨,试图找出BP网络、Hopfield网络方法在水质综合评价中的优缺点,具有非常现实的意义。 相似文献
124.
Xian Liu Lijie Shi Haiyang Qian Shikun Sun Pute Wu Xining Zhao Bernie A. Engel Yubao Wang 《Land Degradation u0026amp; Development》2020,31(8):975-989
China's food security has met standards set by the United Nations Food and Agriculture Organization. However, this development is based on excessive resource input and sacrificing the environment. There are few studies on how to evaluate food production systems with a sustainability framework. In order to guarantee the food security in Northwest China, and realize the sustainable development of agricultural production, this study was carried out. On the basis of comprehensive analysis of new problems faced, including water resources, cultivated land resources and ecological security, several indicators such as water resources development and utilization rate, cultivated land pressure index, cultivated land quality index, N and P emissions and emission intensity are proposed to comprehensively evaluate the sustainability of grain production in Northwest China and put forward countermeasures to realize regional sustainable development. The results show that the water resources are already at a high‐stress level as the development and utilization rate of water resources is 42.7% in 2015. Industrial and domestic water continues to squeeze agricultural water use (annual average reduction of 0.1%). The amount of per capita cultivated land in 2015 has decreased by 9.7% compared to 2000. The quality index of cultivated land is as low as 0.22. A series of ecological problems caused by agricultural production have intensified the ecological crisis in the Northwest, which in turn will further affect food security. Suggestions to address these issues include improving agricultural water use efficiency, strengthening the measures of arable land conservation, improving fertilizer utilization efficiency and reducing plastic‐film mulch residues. 相似文献
125.
126.
Laboratory soil – water systems in which soil organic matter was increased by 0.0%, 0.5%, 1.0%, 2.0% and 4.0% by adding dry, chopped ryegrass (Lolium perenne) shoots to sandy soil containing 0.06% organic matter. Agricultural limestone was added to the systems, and pH, alkalinity and hardness of the water were monitored for 65 days. The pH, alkalinity and hardness increased with greater soil organic matter concentration. Amounts of carbon dioxide released by microbial respiration increased at the higher soil organic matter concentrations, and this resulted in more rapid and greater solubility of agricultural limestone. The results suggest that greater soil organic matter concentrations in ponds favour the rate and extent of agricultural limestone dissolution. 相似文献
127.
油松、刺槐单木与林分水平耗水量的尺度转换 总被引：30，自引：4，他引：30
该文在单木液流测定的基础上 ,采用边材面积作为纯量 ,对京北山区水源保护林的主要树种油松、刺槐林进行由单木到林分耗水的推算 .结果发现 ,两树种边材面积与胸径之间均存在较高的相关性 ,两者之间的关系可以用幂模型得到很好的拟合 .通过实测标准地的胸径分布 ,可以推算出林地边材面积的分布 .利用热脉冲技术测定单木液流通量 ,实时推算林分的实际耗水量 相似文献
128.
We up-scaled the APSIM simulation model of crop growth, water and nitrogen dynamics to interpret and respond to spatial and temporal variations in soil, season and crop performance and improve yield and decrease nitrate leaching. Grain yields, drainage below the maximum root depth and nitrate leaching are strongly governed by interaction of plant available soil water storage capacity (PAWC), seasonal rainfall and nitrogen supply in the water-limited Mediterranean-type environment of Western Australia (WA). APSIM simulates the interaction of these key system parameters and the robustness of its simulations has been rigorously tested with the results of several field experiments covering a range of soil types and seasonal conditions in WA. We used yield maps, soil and weather data for farms at two locations in WA to determine spatial and temporal patterns of grain yield, drainage below the maximum root depth and nitrate leaching under a range of weather, soil and nitrogen management scenarios. On one farm, we up-scaled APSIM simulations across the whole farm using local weather and fertiliser use data and the average PAWC values of soil type polygons. On a 70 ha field on another farm, we used a linear regression of apparent soil electrical conductivity (ECa) measured by EM38 against PAWC to transform an ECa map of the field into a high resolution (5 m grid) PAWC map. We then used regressions of simulated yields, drainage below the maximum root depth and nitrate leaching on PAWC to upscale the APSIM simulations for a range of weather and fertiliser management scenarios. This continuous mapping approach overcame the weakness of the soil polygons approach, which assumed uniformity in soil properties and processes within soil type polygons. It identified areas at greatest financial and environmental risks across the field, which required focused management and simulated their response to management interventions. Splitting nitrogen applications increased simulated wheat yields at all sites across the field and decreased nitrate leaching particularly where the water storage capacity of the soil was small. Low water storage capacity resulted in both low wheat yields and large leaching loss. Another management option to decrease leaching may be to grow perennial vegetation that uses more water and loses less by drainage.Paper from the 5th European Conference on Precision Agriculture (5ECPA), Uppsala, Sweden, 2005 相似文献
129.
K. Vandersypen A. C. T. Keita K. Kaloga Y. Coulibaly D. Raes J.‐Y. Jamin 《Irrigation and Drainage》2006,55(1):51-60
The Office du Niger is a centrally managed collective irrigation scheme of 80 000 ha, mainly cultivated with flooded rice. In the context of recent reforms, water distribution and maintenance at the tertiary canal level were left to farmers. In this paper, their ability to resolve collective action problems through devising, monitoring and enforcing rules is diagnosed through a questionnaire survey of 89 farmers on 59 tertiary canals from five villages. Results show that rules are devised only on 30 and 24% of the canals for water distribution and maintenance respectively. Moreover, there is often no consensus on rules among farmers, and monitoring and sanctioning mechanisms are absent. This results in individualistic behavior causing problems concerning water distribution and maintenance for respectively 20 and 43% of the interviewed farmers. Ineffectiveness of peer pressure and farmers' incomplete mentality shift towards assuming collective responsibility are impediments to successful organization of water management. With water supply being abundant and the infrastructure recently rehabilitated, organization of water management at tertiary level is, however, not always required in order to avoid problems. On the other hand, the current state of affairs is not considered sustainable, as the irrigated area will strongly expand and the irrigation infrastructure ages with time. Measures of sensitization and group empowerment accompanying the process of management transfer will therefore be desirable. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
130.
The reduction in agricultural water use in areas of scarce supplies can release significant amounts of water for other uses. As improvements in irrigation systems and management have been widely adopted by fruit tree growers already, there is a need to explore the potential for reducing irrigation requirements via deficit irrigation (DI). It is also important to quantify to what extent the reduction in applied water through DI is translated into net water savings via tree evapotranspiration (ET) reduction. An experiment was conducted in a commercial pistachio orchard in Madera, CA, where a regulated deficit irrigation (RDI) program was applied to a 32.3-ha block, while another block of the same size was fully irrigated (FI). Four trees were instrumented with six neutron probe access tubes each, in the two treatments and the soil water balance method was used to determine tree ET. Seasonal irrigation water in FI, applied through a full-coverage microsprinkler system, amounted to 842 mm, while only 669 mm were applied in RDI. Seasonal ET in FI was 1024 mm, of which 308 mm were computed as evaporation from soil (Es). In RDI, seasonal ET was reduced to 784 mm with 288 mm as Es. The reduction in applied water during the deficit period amounted to 147 mm. The ET of RDI during the deficit period was also reduced relative to that of FI by 133 mm, which represented 33% of the ET of FI during the deficit irrigation period. There was an additional ET reduction in RDI of about 100 mm that occurred in the post-deficit period. 相似文献