农业病虫害的灾变预测及预报精度分析

在农业病虫害突变规律的研究基础上,建立了定性与定量的尖角突变模型,确定了各病虫的突变区域。根据综合控制变量所确定的边界值,对未来病虫发生发展趋势进行预测。经多年历史资料检验和1992年农业病虫害发生突变的趋势预报证明:准确率高,覆盖面广。     

华北地区主要农业灾害及灾情分析

本文分析了华北地区农业灾害发生的气象背景,并利用1981～1990年的农业统计资料分析了华北地区的农业灾情状况及因灾而造成的粮、棉损失量。华北地区单位耕地面积的受灾率及成灾率分别为47.3%和23.0%,大致相当于二年一遇灾和四年一成灾。华北地区因农业灾害而造成的粮、棉损失量平均每年为397.0和34.5万吨,粮、棉损失率分别为4.9%及15.3%。     

PRIMARY AND SECONDARY IMPACTS OF A WATER RESOURCE DEVELOPMENT PROJECT1

ABSTRACT: At a time in history when water resource development in the United States is being condemned as both economically inefficient and an environmental disaster, perhaps economists need to look back at previous development to see what the fruits of water development (be they sweet or sour) have been. The Boise Project of south-western Idaho is 70 years old and to some people it represents a gross error in resource use, while to others it represents a means of livelihood and well being. A recent research project at the University of Idaho attempted to measure not only the direct economic income benefits of the project (from irrigation), but also the indirect or secondary income benefits (from the food processing industry). Periodic regional input-output tables were constructed to assess the income generated from irrigation and food processing over the period from 1946 to 1970. Input-output analysis allowed researchers to evaluate the direct and indirect impacts of both the irrigation sector and the food processing sector and to compare their growth over time.     

DESALTING SALINE WATER FOR IRRIGATION A CASE STUDY,COACHELLA AREA,CALIFORNIA1

ABSTRACT .A case study was performed to evaluate potential applications of desalted saline water for agriculture using 2 distillation type processes and 2 membrane type processes. The investigation determined the costs and benefits associated with desalting saline water at concentrations of 1,500, 900, 400, 200, and 50 ppm. Benefits from desalting are generated by shifts to more profitable crops, reduced costs for drainage, and reduction in fertilizer and labor requirements with better quality water. Costs are based on the project features such as desalting plants, raw water diversion facilities, storage reservoirs, conveyance and distribution systems, brine disposal, blending facilities, and gypsum addition systems. Hydrologic studies determined the crop irrigation requirements, water demand schedules, desalted water storage requirements, brine disposal requirements, and size of facilities required. Reconnaissance design layouts were made for producing desalted water using a combination of 14 schemes. The study also included a review of irrigation practices. The benefit-cost ratios range from 0.4 to 1.0 for 1,500 ppm irrigation water to 0.8 to 1.0 for 50 and 200 ppm water. Investment costs per acre are high, ranging from $12,900 to $20,900. Irrigation benefits are based on the increase in production from a desert condition with no water supply to the irrigation conditions studied.     

新疆农业生态环境面临的问题与保护措施

新疆农业生态环境面临的主要问题有两大类:一类问题为生态问题;另一类问题为环境污染问题。简要介绍了新疆农业生态环境面临的生态问题,重点介绍了新疆农业生态环境面临的环境污染问题。针对新疆农业生态环境存在的问题,提出了相应的保护措施。     

OCCURRENCE OF TOTAL DISSOLVED PHOSPHORUS IN UNCONSOLIDATED AQUIFERS AND AQUITARDS IN IOWA1

ABSTRACT: Seven sets of ground water samples from 103 observation wells were analyzed for total dissolved phosphorus (TDP) in four areas and five materials including loess and loess derived alluvium in the Deep Loess Hills of western Iowa, outwash and fractured till adjacent to Clear Lake in north central Iowa, fractured till in central Iowa, and a sand and gravel aquifer in northwest Iowa. Land use in ground water recharge zones in all four areas is dominated by crop or animal production or both. Concentrations of TDP exceeding the minimum laboratory detection limit of 20 μg/l as P were found in all areas and in all materials sampled. Samples from the outwash deposits associated with Clear Lake contained significantly larger concentrations than all other areas and materials with a median of 160 μg/l. Water from fractured till in three areas produced the smallest range of concentrations with a median of 40 μg/l. The mean value of TDP in all sample sets exceeded 50 μg/l, an important ecological threshold that causes increased productivity in lakes and perennial streams and one being considered as a surface water nutrient standard by regulatory agencies. These results clearly show that ground water in essentially all near‐surface aquifers and aquitards discharging to Iowa's streams and lakes is capable of sustaining P concentrations of 50 to 100 μg/l in streams, lakes, and reservoirs. Consequently, even if point discharges and sediment sources of P are substantially reduced, ground‐water discharge to surface water may exceed critical thresholds under most conditions.     

Innovative approaches to rural development: Moving from state-controlled towards market-based land reform

Among the world's poor, approximately 75% of those in extreme poverty live and work in rural areas and two‐thirds of them depend mainly on farming or farm labour for their livelihood. Policies to grant the rural poor secure access to land and water for irrigation — and to improve the economic efficiency of small‐scale agriculture — can thus play a critical role in the implementation of rural development strategies, including efforts to combat rural poverty. Since inadequate access to arable land is probably the most important cause of rural poverty, redistributive land reform is increasingly seen as crucial for socio‐economic development and poverty alleviation in many developing countries with substantial amounts of (unused) arable state land or (under‐utilized) large private landholdings. This article argues that market‐based land redistribution schemes, such as the one being implemented in South Africa, can be considered one of the most innovative approaches to land reform that have emerged over the last decade. These schemes thus provide a useful alternative to more conventional, state‐controlled land redistribution programmes. The article concludes, however, that when countries opt for market‐based approaches to land redistribution, the State still has an important role to play, without necessarily deciding which land parcels change hands.     

Operational Indicators for Measuring Agricultural Sustainability in Developing Countries

This paper reviews relevant literature on the sustainability indicators theoretically proposed and practically applied by scholars over the past 15 years. Although progress is being made in the development and critical analysis of sustainability indicators, in many cases existing or proposed indicators are not the most sensitive or useful measures in developing countries. Indicator selection needs to meet the following criteria: relative availability of data representing the indicators, sensitivity to stresses on the system, existence of threshold values and guidelines, predictivity, integratability and known response to disturbances, anthropogenic stresses, and changes over time. Based on these criteria, this paper proposes a set of operational indicators for measuring agricultural sustainability in developing countries. These indicators include ecological indicators involving amounts of fertilizers and pesticides used, irrigation water used, soil nutrient content, depth to the groundwater table, water use efficiency, quality of groundwater for irrigation, and nitrate content of both groundwater and crops. Economic indicators include crop productivity, net farm income, benefit–cost ratio of production, and per capita food grain production. Social indicators encompass food self-sufficiency, equality in food and income distribution among farmers, access to resources and support services, and farmers knowledge and awareness of resource conservation. This article suggests that the selection of indicators representing each aspect of sustainability should be prioritized according to spatial and temporal characteristics under consideration.     

江苏省环境系统特点及环境污染状况

江苏省自然特点为单一而脆弱,表面为平原为主,水域面积较大,山地少,森林覆盖率低,生物种类少,江苏省社会环境特点为人均资源少,经济基础好,交通发达,城市密集和人才优势明显;江苏省的废气,废水,固体,噪声污染日益严重。由于上述特点和原因,江苏省农业机械化,现代化程度较高,水产养殖业发达,但应进一步提高农业集约化程度和大力推广生态农业整治环境污染,利用天在河道进一步发展养殖业;江苏省工业轻,重并举以轻为     

资源工程体系建设探讨——以三峡库区坡地资源开发保护体系建设为例

资源工程是实现社会经济发展的基本途径。资源开发体系和保护体系建设是构成资源工程体系的主要内容。文章阐述了如何设计一个资源开发和保护体系的总体思路（包括原则、目标、内容、行动、效益评估）,并以长江三峡库区坡地资源利用保护为例,通过植物篱农林复合技术,使水土流失和环境退化基本得到了控制,经济产出比纯柑桔系统和纯粮食作物系统分别高出１／５和１／４,成为开发与保护融为一体、经济和生态相互促进的技术。这一技术值得在中国东部湿润半湿润区域推广。