2001年农作物病虫害发生流行的气候影响评价

综合分析了 2001年气候条件对全国农作物病虫害发生流行的影响.春夏季全国大范围的持续严重高温干旱,造成全国农作物病虫害偏重发生,其特点是虫害重于病害,全国大部分地区以虫害为主,病害较轻.春夏季的高温干旱引发蝗虫全国大发生,但制约了小麦病虫害的严重发生,为中等发生年.全国主要稻区病虫害发生期间干旱、少雨、大雨频次低,限制了水稻病虫害的严重发生,为中等发生年.水稻稻飞虱中等偏轻发生,但造成长江流域水稻螟虫的中等偏重发生.东北、华北地区中后期温度降水配合相对适宜,造成玉米螟中等偏重发生.     

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.     

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。     

SUPPLEMENTAL IRRIGATION OF HORTICULTURAL CROPS IN THE HUMID REGION1

ABSTRACT: A computer model was developed in order to establish a yield predictive relationship and to estimate the water requirements for supplemental irrigation of horticultural crops in the humid region. Alternative distribution systems were developed and designed using the results from the computer model and Wood's (1980) pipe network algorithm. The capital, operational, and maintenance costs of the distribution and recommended on-farm irrigation systems were determined and used to evaluate the economic feasibility of the alternative designs. Results show that the concentration of irrigated area along the distribution system, the length of the distribution system, and cropping system all have an important effect on the economic feasibility of supplemental irrigation in Wayne County, Kentucky.     

德昌旱地粮菜四熟种植模式的效益和能量分析

德昌县旱地粮菜四熟模式是一年生产一季玉米和三季蔬菜。该模式可充分利用安宁河中下游丰富的温光资源,一年内亩产粮食627.5kg,蔬菜总计11935kg,经济收入2430.4元。其光能利用率达3.864%,能量产投比2.15,是适合城郊区旱地种植的一种较好模式。进一步增施磷钾肥是本模式获得更多农产品、提高资源利用率、维持和培肥土壤的重要措施。     

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.     

OPTIMAL OPERATION OF SHELBYVILLE AND CARLYLE LAKES1

ABSTRACT: Dams were built by the U. S. Army Corps of Engineers on the Kaskaskia River at Shelbyville and Carlyle in Illinois, in 1969 and 1967, respectively. The operation of the Shelbyville and Carlyle Lakes has changed over the years because of considerably lower bankfull channel capacities downstream of the dams than were adopted in the project designs. This study was conducted to review the present operation policy. Intent was to derive a policy for maximizing the overall benefits (or minimizing the overall damages) and to compare these benefits or damages with those with the present policy. The operating rules were optimized through a simulation model which was structured considering the physical nature of the system and the desirable operation in the best interest of various beneficial uses. The expected annual value of overall benefits from recreation and agriculture is shown to increase by $0.2 million with the optimal policy. With the optimal operation, the overall damages are reduced by 76 percent on the average over the 24 years of flow record at Shelbyville and Carlyle.