The potential of small-scale rainfed agriculture to strengthen food security in Arab countries

In most Arab countries, domestic agricultural production is insufficient. The gap between production and demand is likely to increase due to climate change and other factors. This review paper examines the challenges and possible solutions to ensuring food security in the future. It focuses on rainfed agriculture, which accounts for two-thirds of the region’s cropland, the bulk of its food staples, and almost all its rangelands. Given the scarcity of water and arable land, there are few opportunities in the region to expand cultivated area. But numerous effective, proven technologies are available that can increase productivity per unit area of land or volume of water. Crop technologies include, for example, new stress-tolerant varieties, supplemental irrigation and other techniques to increase water productivity, and conservation agriculture and other land management methods. Livestock nutrition and productivity could be increased with new forage or dual-purpose varieties, and greater use of alternative feed sources such as feed blocks made from crop by-products. The paper describes some of these technologies, and summarizes results obtained from on-station and on-farm testing. The key issue is poor adoption of available technologies. The priority for researchers and policy makers must therefore be to scale up investments in research and extension; encourage private sector participation; and create enabling policies to encourage technology adoption, market participation and more sustainable use of natural resources, by smallholder farmers.     

联合生物加工在生物质能源生产中的作用

生物质能源在保障能源安全方面正起到越来越重要的作用.联合生物加工相对于其它的生物质转化工艺具有明显的优势.茵株改造策略及酶-微生物协同机制的研究将推动联合生物加工的进一步发展.     

Atmospheric lifetime and global warming potential of a perfluoropolyether

Perfluoropolyethers (PFPEs) are a family of perfluorinated fluids used mainly in industrial applications. Lower molecular weight commercial PFPE fractions have boiling points ranging between 55 and 270 degrees C, and have the potential to escape into the atmosphere. To improve our understanding of the atmospheric chemistry of PFPEs, a distilled fraction of a commercial mixture containing perfluoropolymethylisopropyl ethers (PFPMIEs) was introduced into an atmospheric chamber system. Relative rate techniques were used to determine upper limits for the rate constants for reactions of OH and Cl with PFPMIE in 700 Torr of air at 296 K. The reactivity of PFPMIE with Cl was less than 2 x 10(-17) cm3 molecule(-1) s(-1), while the reactivity with OH was less than 6.8 x 10(-16) cm3 molecule(-1) s(-1), indicating low reactivity in the troposphere. Consequently, the lifetime of PFPMIE should be limited bytransport to the mesosphere, where photolysis by Lyman-alpha radiation at 121.6 nm will be efficient. By analogy to perfluorinated alkanes, the lower limit for the total atmospheric lifetime is 800 years. PFPMIE was shown to have instantaneous radiative forcing of 0.65 W m(-2) ppb(-1), which corresponds to a global warming potential on a 100 year time scale of 9000 relative to CO2 and 1.95 relative to CFC-11.     

The energetics of British agriculture

An analysis is presented firstly of the biological energetics of UK agriculture in which the ultimate yield of edible food is related to primary plant production and solar radiation incidence. Secondly, the industrial energetics of British agriculture are dealt with in which agriculture is regarded as an industry in which the input is of materials which have required, for their production, energy as fossil fuel and the output is again edible food. The results show that primary plant output is 0.18% of solar radiation receipt and of this 12% is recovered as human food. This meets 57% of the requirements of the population for dietary energy and the labour of one man supports the dietary requirement of 48 people. UK agriculture accounts for 3.9% of the total UK primary fuel consumption and the farm gate output relative to total fossil fuel input is 0.6 : 1 while the edible food output is 0.3 : 1. The results of the analysis are discussed taking both a short term and long term view.     

Typical dioxin concentrations in agriculture soils of Washington state and potential sources

Background or typical levels of polychlorinated dibenzo-p-dioxins and of polychlorinated dibenzo-p-furans in soils have become increasingly important in the regulatory community, as dioxins have come under increased scrutiny due to their toxicity and persistence. Knowing the typical levels of dioxin in soils is important to set regulatory levels, to prevent further contamination, and for setting cleanup levels. A random sample (n=54) of agricultural lands within Washington state revealed a typical concentration of "dioxin" of 0.14 ng/kg (toxicity equivalents, TEQ). For a comparison, residential urban areas, forested, and open areas were also investigated on a smaller scale (n=14, 8, and 8, respectively) with typical dioxin values of 4.1, 2.3, and 1.0 ng/kg (TEQs), respectively. A discriminant function analysis was used to examine soil dioxin profiles and associations with potential known dioxin sources in Washington state. Soil sample dioxin profiles could not be discriminated from those of biosolids and pentachlorophenol products.     

Evaluation of global onshore wind energy potential and generation costs

In this study, we develop an updated global estimate of onshore wind energy potential using reanalysis wind speed data, along with updated wind turbine technology performance, land suitability factors, cost assumptions, and explicit consideration of transmission distance in the calculation of transmission costs. We find that wind has the potential to supply a significant portion of the world energy needs, although this potential varies substantially by region and with assumptions such as on what types of land can be used to site wind farms. Total global economic wind potential under central assumptions, that is, intermediate between optimistic and pessimistic, is estimated to be approximately 119.5 petawatt hours per year (13.6 TW) at less than 9 cents/kWh. A sensitivity analysis of eight key parameters is presented. Wind potential is sensitive to a number of input parameters, particularly wind speed (varying by -70% to +450% at less than 9 cents/kWh), land suitability (by -55% to +25%), turbine density (by -60% to +80%), and cost and financing options (by -20% to +200%), many of which have important policy implications. As a result of sensitivities studied here we suggest that further research intended to inform wind supply curve development focus not purely on physical science, such as better resolved wind maps, but also on these less well-defined factors, such as land-suitability, that will also have an impact on the long-term role of wind power.     

The effect of improving cow productivity, fertility, and longevity on the global warming potential of dairy systems

This study compared the environmental impact of a range of dairy production systems in terms of their global warming potential (GWP, expressed as carbon dioxide equivalents, CO₂-eq.) and associated land use, and explored the efficacy of reducing said impact. Models were developed using the unique data generated from a long-term genetic line × feeding system experiment. Holstein-Friesian cows were selected to represent the UK average for milk fat plus protein production (control line) or were selected for increased milk fat plus protein production (select line). In addition, cows received a low forage diet (50% forage) with no grazing or were on a high forage (75% forage) diet with summer grazing. A Markov chain approach was used to describe the herd structure and help estimate the GWP per year and land required per cow for the 4 alternative systems and the herd average using a partial life cycle assessment. The CO₂-eq. emissions were expressed per kilogram of energy-corrected milk (ECM) and per hectare of land use, as well as land required per kilogram of ECM. The effects of a phenotypic and genetic standard deviation unit improvement on herd feed utilization efficiency, ECM yield, calving interval length, and incidence of involuntary culling were assessed. The low forage (nongrazing) feeding system with select cows produced the lowest CO₂-eq. emissions of 1.1 kg/kg of ECM and land use of 0.65 m²/kg of ECM but the highest CO₂-eq. emissions of 16.1 t/ha of the production systems studied. Within the herd, an improvement of 1 standard deviation in feed utilization efficiency was the only trait of those studied that would significantly reduce the reliance of the farming system on bought-in synthetic fertilizer and concentrate feed, as well as reduce the average CO₂-eq. emissions and land use of the herd (both by about 6.5%, of which about 4% would be achievable through selective breeding). Within production systems, reductions in CO₂-eq. emissions per kilogram of ECM and CO₂-eq. emissions per hectare were also achievable by an improvement in feed utilization. This study allowed development of models that harness the biological trait variation in the animal to improve the environmental impact of the farming system. Genetic selection for efficient feed use for milk production according to feeding system can bring about reductions in system nutrient requirements, CO₂-eq. emissions, and land use per unit product.     

Production potential of plateau agriculture and food sufficiency in the Kandhamal district of Orissa

The requirement for food grains in the rainfed hill plateaus of the Kandhamal district of the State of Orissa, India was calculated according to accepted nutritional standards over 14 years from 1993 to 2006 and compared with actual production during this time. Owing to the increase in population, the requirement increased from 120 × 10³ MT in 1993 to 142 × 10³ MT in 2006. Production, however, ranged from 68.5 × 10³ MT in 2002 to 134.9 × 10³ MT in 1994 and was only sufficient in 2 of the 14 years. The requirement for food grains for a projected population of 753,542 in 2011 was estimated to be 152 × 10³ MT. At present the area sown is 115 × 10³ ha and would require cultivation 1.83 times per year (cropping intensity 1.83) to produce enough foodgrains for nutritional sufficiency. This could be reduced to 1.64 if the current fallow area of 13 × 10³ ha were cultivated. Increased productivity could be achieved by greater use of irrigation and groundwater.     

超临界流体技术在微藻生物能源中应用

微藻具有光合作用效率高、含油量高、生长周期短、油脂面积产率高等特点,微藻生物能源已成为近年国内外生物能源及CO2减排领域研究热点,被誉为最具发展潜力"第三代"生物能源。超临界流体技术是一种新型高效绿色分离技术,广泛应用于食品、医药和化工等领域。该文综述超临界流体技术在微藻生物能源技术方面应用,主要包括利用超临界流体提取微藻油脂、不饱和脂肪酸、色素和其它活性物质,及在超临界流体中液化微藻生物质等。     

一个国土狭小的食品出口大国——访荷兰驻中国大使馆农业随员荷兰生先生

荷兰本土面积仅41,526平方公里,约为中国的二百三十分之一,人口却多达1,560万,是世界人口最密集的国家之一。随着近年来环保意识的增强,荷兰政府对农药、化肥的使用严加控制,并对本已很少的耕地面积进行下调。然而,这却丝毫没有影响其农产品的产量,荷兰至今仍保持着世界第三大农业和食品出口国的地位。究竟是什么使荷兰在一片狭小的土地上创造出如此惊人的业绩?记者就此采访了荷兰驻我国大使馆农业随员荷兰生(Frans A.G.M.Claassen)先生。     

农林机械液压系统的正确维护与保养

结合农林机械液压系统在使用过程中容易出现的故障,介绍了液压系统维护保养的具体方法,并提出了在使用中应注意的一些问题.     

非织造材料的农业应用和发展

阐述了农用非织造材料的特点、作用机理、应用情况和性能要求,指出我国非织造材料在农业方面的应用前景广阔。     

The role of organic agriculture in the dairy industry

A small, but high added-value and growing market exists for dairy produce manufactured from milk produced organically. This paper describes the philosophy and practice of organic agriculture and suggests its relation to the dairy industry.     

啤酒废酵母中还原型谷光甘肽提取

谷胱甘肽（GSH）是一种天然的活性短肽,具有清除体内自由基等生理功能。本文分别采用微波辅助法、热水抽提法和其它抽提法从啤酒废酵母中提取GSH,主要探讨了微波辅助法和热水抽提法的提取工艺条件,分析比较了不同方法的提取效果。结果表明：热水抽提和微波处理是两种简便、有效的方法,其中微波法具有好的应用前景。     

啤酒废酵母中还原型谷光甘肽提取

谷胱甘肽（GSH）是一种天然的活性短肽,具有清除体内自由基等生理功能。本文分别采用微波辅助法、热水抽提法和其它抽提法从啤酒废酵母中提取GSH,主要探讨了微波辅助法和热水抽提法的提取工艺条件,分析比较了不同方法的提取效果。结果表明：热水抽提和微波处理是两种简便、有效的方法,其中微波法具有好的应用前景。