ECONOMIC ANALYSIS OF WATER-SAVING TECHNIQUES IN IRAN1

ABSTRACT: The possibility of increasing the water supply for irrigation through adoption of more efficient water-application techniques as an alternative to new irrigation projects was studied in an irrigated region of Iran. Excessive water application at the farm level ranks high among the causes of water shortages in the selected region. An empirical analysis of the effect of water-saving technology on the farm operator's net return was made choosing two farms in the region as a case study. The problems facing these farms are common to most farms throughout the country. The results of the budgeting analysis of the selected farms indicated that an improvement in irrigation technique can result in the expansion of water supply and higher marginal value product for water. Comparing the costs of irrigation systems with the net returns resulting from the higher efficiency showed that such an investment is economically feasible.     

湛江市农业土壤与作物铬含量及其健康风险

在湛江市采集了106个农业土壤表层样品和43个农作物样品,分析了土壤和农作物中铬的含量,研究铬的分布特征和富集能力,评价其健康风险。结果表明:土壤中铬平均含量为87.13mg/kg,超过国家土壤二级标准的样品占20.75%,徐闻、雷州等地超标较严重。湛江市种植面积及产量最大的4大类农作物蔬菜、水果、甘蔗和水稻铬平均含量介于0.014～0.160mg/kg之间,均符合我国《食品中铬限量卫生标准》(GB 14961-1994)。蔬菜类的芥菜铬的富集能力相对较强,青瓜、菜心、生菜等蔬菜品种和菠萝、香蕉、橙子、甘蔗等水果类铬的富集能力则较低;水稻铬的富集能力容易受土壤复合污染影响,富集系数介于0.0001～0.0048。依据中国营养学会推荐的RfD值和广东省居民平均食物消费结构进行计算,湛江市蔬菜、水稻和水果(含甘蔗)三大类作物通过土壤-植物-人体途径日平均摄入量为78.9μg/d,若考虑其它的摄入途径,农产品中的铬对人体潜在一定的健康风险。     

桔园间作牧草的生态效益及其管理技术

在浙江省金华地区新垦植的红壤幼龄桔园及盛产成龄桔园进行了间作试验和调查研究。结果表明，幼龄桔园间作黑麦草或紫云英，能提高光能利用率，具有延缓秋冬土壤降温和春季土壤升温、减小土壤日温差幅度和冬季保暖、降低水土流失量等生态效应，但对夏梢生长具有不良的影响；成龄桔园长期间作紫云英也具有提高光能利用率，维持较高的肥料养分效率，明显改善土壤肥力，提高产量和改善柑桔外观品质等多种效益。桔园间作牧草应结合柑桔生产的要求，抓住适时拌肥播种、及时收割施肥和适时适量归还土壤３个管理技术要点。     

厌氧消化治理造纸黑液

造纸黑液是最严重的水污染物之一,目前国内还没有一种能彻底治理黑液的方法,球溪河糖厂经过多年探索,试验,工业化治理运行,认为厌氧消化是治理中小型,亚铵法纸厂制浆黑液适宜方法。     

Winter losses of nitrogen and phosphorus from Italian ryegrass, meadow fescue and white clover in a northern temperate climate

We have studied to what degree Italian ryegrass (Lolium multiflorum Lam.), white clover (Trifolium repens L.) and meadow fescue (Festuca pratensis L.) are able to preserve nitrogen (N) and phosphorous (P) in shoots and roots from one growing season to the next in a northern temperate climate. Field experiments were performed during four consecutive winters in central southeast Norway (60°42′N, 10°51′E), and N and P in plant biomass were measured in the autumn and in the spring. We also measured the contents of total N, total P and organic carbon (C) in seepage water that percolated through the aboveground plant material. Uptake of N and P in Italian ryegrass and white clover was substantially larger than in meadow fescue. The winter losses varied greatly from year to year, depending on the winter climate. On the average for all three of the plant species, the winter losses of N from aboveground biomass were 6, 35, 68 and 10% in the four experimental years, respectively. The corresponding P losses were 11, 36, 60 and 22%. On the average for all plant species and experimental years, 43 (±12)% (S.E., n = 12) of the N, 34 (±9)% of the P and 4 (±1)% of the C that was lost from the aboveground plant biomass during the winter, was recovered in seepage water, basically as a nutrient pulse in melt water in early spring. The very low C recovery rate in seepage water suggested a considerable microbial growth on lost plant C. Assuming that all un-recovered plant C was consumed by microorganisms not included in measurements of the seepage water, modelling showed that microbial immobilisation theoretically might explain the unexpectedly low recovery rates of N and P. The study was not designed to investigate the possible effects of psychrophilic microbes on N and P cycling. Therefore, it is inconclusive and underlines the need for more knowledge on this matter.     

黄土高原降水的季节性指标及其与作物水分亏缺的关系

黄土高原位于我国东部季风区与西部非季风区之过渡地区,属弱季风区,降水相对较集中。为分析本区降水的时空分布,文中采用矢量合成方法计算了黄土高原296个站的降水季节性指标值及降水季节,前者变化于0.44—0.64 之间,后者集中于7月中、下旬至8月上旬,自东南向西北推迟。降水的季节性指标与降水季节直接影响到作物水分的亏缺量,全区小麦严重缺水100—200mm 不等,玉米缺水30—50mm,而谷子生育期中水分需求基本可以得到满足。最后,讨论了本区降水与土壤水分含量的关系,指出本区水分不足,认为有的作者提出的该区尚有80％的水分潜力没有得到发挥的见解是错误的。     

试论黄淮海地区的自然资源及国家级作物商品基地的建设

根据中国主要农业区--黄淮海地区的自然和社会经济条件,分析了该区小麦、玉米、大豆、棉花等在气候-土壤生态适应性的基础上,采用逐级生产力估算方法,计算出四大作物的商品量,论证了该地区建设为全国性四大作物商品基地的可能性。     

Variations in land requirements for meat production

Production of meat requires substantial amounts of feed grains which in turn require vast amounts of land. Future population growth and increase in consumption will raise the demand for meat and with it the land required for meat production. This paper analyses the various factors that affect land requirements for meat production. Meat production by Dutch broilers, pigs and beef cattle on their current feeds are compared and options for change are evaluated with respect to their nutritional needs. Differences in land requirements of a factor of 3 were found between different agricultural production systems and feeds as well as between types of livestock. It is shown that broilers have the lowest land requirement while beef cattle have the highest. The variation in feed crop yields between agricultural systems is discussed. It is concluded that due to the large variation within the system there is potential for reduction in the land requirements for meat production.     

典型污灌区土壤与作物中重金属健康风险评估

该文选取了国内外9个典型污灌区作为研究对象,分析了重金属在土壤及作物中的污染情况,评价了重金属对人体健康造成的风险.结果表明,总体而言同一灌区重金属在小麦中富集浓度高于玉米.其中超标最严重的是德国柏林（BL）地区的Cd,在玉米和小麦中浓度分别为1.62、7.50mg/kg,分别是WHO/FAO标准的8.1和37.5倍,这和BL灌区土壤中Cd浓度高有关.口食小麦对人体健康造成的风险分别在10^-6~10^-4a^-1之间.致癌性重金属Cd通过口食小麦途径对成人和儿童健康造成的风险分别占总风险的61.75~99.93%、60.78~99.84%.重金属在各种暴露途径下对儿童产生的风险大于成人.BL、津巴布韦的Harare（HR）、墨西哥的Mezquital（MQ）和沈阳珲浦（JP）灌区重金属对成人和儿童健康造成的总风险分别为5.12×10^-5~7.53×10^-4、5.71×10^-5~8.37×10^-4,超出USEPA和ICRP相关规定,其中污染最严重的地区是BL.     

上海地区主要农作物气象灾害评估预测警示系统的研究

主要农作物气象灾害评估预测警示系统网页共有二部分内容：历年灾害动态对比和早涝趋势预测与警示。历年灾害动态对比是对比1991年以后上海地区主要表l作物气象灾害的变化情况。早涝趋势预测是在降水趋势预测基础上，对未来月或农时段降水量进行预测。