Crop losses: The need to quantify the effects of pests,diseases and weeds on agricultural production

Crop losses caused by pests, including rodents and birds, and by diseases and weeds, are defined, and previous studies reviewed. Information about losses is needed to monitor the effects of pests and diseases on crop production, in individual countries and worldwide, important for food policy and economic reasons; to make decisions and allocate resources on the study, management and control of pests and diseases; to stimulate action against them; to provide guidelines for research on crop improvement to prevent pest and disease attack; and as a basis for judgement on the importance of pests, diseases and weeds in relation to agriculture and the environment.The causes of such losses, why information must be up to date, and methods of assessing pests, diseases, weeds and losses are examined. The part played by losses in the development and use of economic pest and disease control action thresholds is discussed, including pest, disease, crop, climatic, economic and farmer attitude factors. The types of relation between yield and pest and disease attack are reviewed, how to measure the relation in practice, how to obtain different amounts of attack, surveys of losses, and the difficulties met in the study of losses: interaction; compensation; interplot interference; variation; and distribution. Sources of information on world losses, training and the work of the FAO are reviewed. General guidelines on crop loss assessment are given.     

Typologies of crop-drought vulnerability: an empirical analysis of the socio-economic factors that influence the sensitivity and resilience to drought of three major food crops in China (1961–2001)

Why is it that sometimes small droughts trigger serious crop losses while in other cases even large droughts do not have such a major effect? In this paper, we identify socio-economic indicators associated with sensitivity and resilience to drought for each of China's main grain crops (rice, wheat and corn). Provincial harvest and rainfall data (1961–2001) are used to calculate an annual “crop-drought vulnerability index”. We separate “sensitive cases” (where significant harvest losses occurred in years with only minor droughts) and “resilient cases” (where harvest losses were minimal despite there being a major drought) and explore the socio-economic characteristics of these different situations. Results show that sensitive cases were particularly common in economically poor landlocked provinces and in wealthy coastal areas that have a limited land base. In such “sensitive cases”, the size of the rural population and the quantity of agricultural inputs were negatively correlated with drought vulnerability, while for resilient cases, vulnerability was negatively correlated with the abundance of land. This leads us to propose a series of drought-vulnerability typologies based on the extent to which land, labour, capital, agricultural technology, and infrastructure buffer or exacerbate the effect of a drought event.     

秸秆焚烧对玉溪市大气PM10的影响解析研究

以水溶性钾为示踪元素,解析秋收季节秸秆焚烧对玉溪市大气PM10的贡献.结果表明,2001年秋收季节(10月)水溶性钾浓度(7.68μg/m3)比夏季水溶性钾浓度(2.38μg/m3)高3.2倍,与7月至12月份PM10浓度变化呈显著相关,相关系数为0.810.很显然,秋收季节秸秆焚烧对玉溪市大气PM10有负面影响.     

The selection of management strategies for controlling nematodes in cereals

Several genera and species of plant-parasitic nematodes cause losses in grain yield in cereals; some are of relatively minor importance (e.g. Anguina tritici (Steinbuch) Chitwood, the cause of “ear cockle” in wheat), while others such as the cereal cyst nematode (CCN) (Heterodera avenae Woll.) have a wide geographic distribution, infest extensive areas, and may cause losses valued at millions of dollars. Some of these nematodes are difficult to control because the measures that might be used are uneconomic to apply or are impractical. The control of CCN, however, can be achieved, and several successful strategies have been developed in parts of Europe and in Australia. The various measures available to Australian cereal growers include: crop rotation, resistant cultivars, manipulation of sowing dates, use of nematicides, and reduced cultivation. The selection of an appropriate management strategy for the control of CCN is influenced by factors such as: climate, cereal species grown, yield potential, rotations practised and the availability of alternative crops, pathotype present, farm size, availability of resistant cultivars, nematicides registered, and the availability of suitable equipment for their application.     

Soil loss due to harvesting of various crop types in contrasting agro-ecological environments

Soil erosion studies on cropland usually only consider water, wind and tillage erosion. However, significant amounts of soil are also lost from the field during the harvest of crops such as sugar beet (Beta vulgaris L.), potato (Solanum tuberosum L.), chicory roots (Cichorium intybus L.), cassava (Manihot spp.) and sweet potato (Ipomoea batatas (L.) Lam). During the harvest soil adhering to the crop, loose soil or soil clods and rock fragments are exported from the field together with these crops.This soil erosion process is referred to as ‘soil losses due to crop harvesting’ (SLCH). Most of the studies investigated SLCH variability and its controlling factors for one crop type in similar agro-ecological environments and for comparable harvesting techniques. In this study, a compilation of SLCH studies was made in order to investigate the effect of crop type, agricultural systems, ecological conditions and harvesting technique on SLCH variability. SLCH rates ranged from few to tens of Mg ha⁻¹ harvest⁻¹ and SLCH was highly variable both in space and time. Comparison of four studies on SLCH for sugar beet revealed that harvesting technique and soil moisture content at harvesting time can be equally important for SLCH variability. The occurrence of soil clods harvested with the crop explained why SLCH was significantly larger for mechanically harvested potato in Belgium compared to manually harvested potato in China. SLCH values for manually harvested sugar beet, potato, cassava and sweet potato in China and Uganda were in general smaller than SLCH values for mechanically harvested sugar beet, potato and witloof chicory roots measured in Belgium and France. However, SLCH may also vary significantly within Europe due to differences in harvesting techniques. Soil moisture content at harvesting time was besides harvesting technique one of the key factors controlling SLCH variability. There were no systematic differences in SLCH between crop types, although the soil–crop contact area–crop mass ratio could explain more than 40% of the means from several SLCH studies.     

矿山复垦土壤典型元素时空变化研究

在抚顺矿区矸石回填复垦还田生态重建试验区,利用网格布点取样法采集不同覆土类 型、不同土壤深度、不同覆土时间的土壤样品,对矿山复垦土壤的营养元素和重金属元素的 时空变化进行了研究.结果表明,矸石回填覆土后,营养元素含量在覆土初期恢复较快,覆土中 重金属元素含量呈逐年递减趋势;施(培)肥造成了重金属元素和营养元素含量表层高于30cm 层和60cm层;覆土中重金属元素主要来源于外界输入; 矸石母质中的重金属不存在对覆土耕 作层的污染问题.     

SUSTAINABLE DEVELOPMENT AND HAZARDS MITIGATION IN THE UNITED STATES: DISASTERS BY DESIGN REVISITED

It has become clear that natural and related technological hazards and disasters are not problems that can be solved in isolation. The occurrence of disasters is a symptom of broader and more basic social problems. Since 1994, a team of over 100 expert academics and practitioners – including members of the private sector – have assessed, evaluated, and summarized knowledge about natural and technological hazards in the United States from the perspectives of the physical, natural, social, behavioral, and engineering sciences. The major thesis of the findings was losses from hazards and inability to comprehensively reduce losses of all types are the consequences of narrow and shortsighted development patterns, cultural premises, and attitudes toward the natural environment, science, and technology. To address these broad and basic problems, the study included proposals for ways in which people and the institutions of the United States can take responsibility for disaster losses, reduce future hazard losses, and link hazard mitigation to sustainable development.     

Estimating yields of tropical maize genotypes from non-destructive,on-farm plant morphological measurements

Maize is the main grain crop grown in the highlands of sub-Saharan Africa, on a broad range of soil fertility and management conditions. Important yield variability has been reported at different scales, reflecting the intensity and spatial distribution of growth-limiting and growth-reducing factors. Maize yield estimation represents a valuable tool to assess within-farm variability in soil fertility through crop performance. The objective of this study was to develop mathematical relationships between plant morphological attributes and grain yield of tropical maize genotypes, based on plant allometric characteristics. These models were used to estimate maize yields and the estimates were validated against independent data collected from experimental and farmers’ fields in western Kenya. Three commercial hybrids and three local varieties were considered. Multiple linear regression models including plant height and either ear length or ear diameter as explanatory variables, and simple linear regressions including only plant height, were the most accurate to estimate both total aboveground biomass and grain dry matter yields per plant (r²: 0.76–0.91). Average values for the harvest index ranged between 0.34 and 0.42, varying with the total aboveground biomass produced per plant. Yield estimations on ground area basis for farmers’ fields were acceptably accurate. Plant height measurements can be easily taken at any moment after maize flowering and used in simple models to estimate maize yield. This approach proved also a valuable tool to discuss yield variability with farmers.     

Estimating changes in flood risks and benefits of non-structural adaptation strategies - a case study from Tyrol,Austria

Flood damage has increased significantly and is expected to rise further in many parts of the world. For assessing potential changes in flood risk, this paper presents an integrated model chain quantifying flood hazards and losses while considering climate and land use changes. In the case study region, risk estimates for the present and the near future illustrate that changes in flood risk by 2030 are relatively low compared to historic periods. While the impact of climate change on the flood hazard and risk by 2030 is slight or negligible, strong urbanisation associated with economic growth contributes to a remarkable increase in flood risk. Therefore, it is recommended to frequently consider land use scenarios and economic developments when assessing future flood risks. Further, an adapted and sustainable risk management is necessary to encounter rising flood losses, in which non-structural measures are becoming more and more important. The case study demonstrates that adaptation by non-structural measures such as stricter land use regulations or enhancement of private precaution is capable of reducing flood risk by around 30 %. Ignoring flood risks, in contrast, always leads to further increasing losses—with our assumptions by 17 %. These findings underline that private precaution and land use regulation could be taken into account as low cost adaptation strategies to global climate change in many flood prone areas. Since such measures reduce flood risk regardless of climate or land use changes, they can also be recommended as no-regret measures.     

猪粪还田对土壤硝态氮淋失的影响研究——以黄灌区稻旱轮作制为例

宁夏引黄灌区是水污染严重地区之一,大部分排水沟水质属于劣五类,主要污染物是硝态氮与铵态氮.猪粪还田试验共有3个处理:传统施肥+空白(CK)、传统施肥+猪粪还田4500 kg/hm²(T1)和传统施肥+猪粪还田9000 kg/hm²(T2).采用树脂芯法测定了30,60,90cm土层的硝态氮淋失量.结果表明,30cm土层处,猪粪还田没有明显增加土壤硝态氮淋失.与对照(15.96±0.41) kg/hm²相比,T1(16.85±0.40) kg/hm²与T2(17.01±0.46) kg/hm²没有达到显著差异(P>0.05);60cm土层处理与对照也没有达到显著差异;90cm土层处的猪粪处理与对照达到显著差异,处理之间没有差异.猪粪还田有利于土壤有机质和总氮提高,30cm土层,与对照相比,T1和T2的有机质增加0.95g/kg和1.41g/kg,分别提高7.50%和11.13%;总氮增加0.06和0.16g/kg,分别提高7.72%和22.04%.猪粪还田提高了作物产量,水稻增产12.26%~11.56%,冬小麦产量提高9.32%~12.52%.     

The 316(b) assessment process: evolution towards a risk-based approach

Since its inception, the 316(b) assessment process has undergone considerable evolution and refinement. In this paper, the authors review and discuss this evolutionary process focusing on several key scientific findings. Among these are that the potential for adverse environmental impact is relatively low for many ecosystem components (e.g., phytoplankton, microzooplankton); that the survival of entrained organisms is often quite high; that the prediction of adverse environmental impact is hampered by the present inability to effectively quantify compensatory processes; and that subsequent monitoring has revealed that the dire population consequences originally predicted for several aquatic populations have not been borne out. While this evolution has resulted in less divergence in the estimates of cooling water-related losses between the regulatory and regulated communities, accurate determination of the population level consequences of such losses remains elusive. This uncertainty makes final resolution of 316(b)-related issues difficult. To address these difficult issues, we propose an assessment approach based on an ecological risk framework coupled with adaptive resource management. This approach begins with a screening process which helps to focus the assessment on the key resources at risk, followed by a “weight-of-evidence” evaluation of all relevant predictive and retrospective information, and concludes with an evaluation of the relative cost and benefits of intake alternatives and the need for additional monitoring. Such an approach has been successfully employed at several large-scale 316(b) assessments completed in recent years and provides a mechanism for dealing with uncertainties in the assessment process, while at the same time ensuring reasonable protection of the environment.     

Differential N uptake by maize cultivars and soil nitrate dynamics under N fertilization in West Africa

Nitrate is prone to leaching in the sandy soils of the West African moist savannas. Better management of nitrogen (N) resources and maize cultivars with enhanced genetic capacity to capture and utilize soil and fertilizer N are strategies that could improve N-use efficiency. In two field experiments conducted at Zaria, northern Nigeria, five maize (Zea mays L.) cultivars planted early in the season were assessed under various N levels for differences in N uptake, soil N dynamics, and related N losses. Cultivar TZB-SR accumulated more N in the aboveground plant parts in both years than the other cultivars. All, except the semi-prolific late (SPL) variety, met about 50–60% of their N demand by the time of silking (64–69 DAP). In both years, SPL had the greatest capacity to take up N during the grain filling period, and it had the highest grain-N concentration and the least apparent N loss through leaching in the second year. There were no significant differences in soil N dynamics among cultivars in both years. At harvest, the residual N in the upper 90 cm of the profile under all the cultivars ranged from 56 to 72 kg ha⁻¹ in the first year and from 73 to 83 kg ha⁻¹ in the second year. Apparent N loss from 0 to 90 cm soil profile through leaching ranged from 35 to 122 kg ha⁻¹ in both years. N application significantly increased N uptake by more than 30% at all sampling dates in the second year of the experiment, but had no effect on apparent N loss. Results indicate that the use of maize cultivars with high N uptake capacity during the grain filling period when maximum leaching losses occur could enhance N recovery and may be effective in reducing leaching losses of mineral N in the moist savanna soils.     

Spatial and long-term variability of soil loss due to crop harvesting and the importance relative to water erosion: A case study from Belgium

The harvest of crops such as sugar beet (Beta vulgaris L.), potato (Solanum tuberosum L.), leek (Allium porrum L.) and carrot (Daucus carota L.) causes soil loss from arable land because soil adhering to the crop and soil clods that failed to be separated by the harvesting machine, are exported from the field together with these harvested crops. These soil losses can be of the same order of magnitude as soil losses caused by water erosion processes, but are often neglected in soil erosion research. In this article we developed a methodology to investigate the spatial and long-term (1846–2004) variability of soil loss due to crop harvesting (SLCH) in Belgium and the spatial distribution of the importance of SLCH relative to soil losses caused by water erosion processes in Flanders. The study is based on long-term time series of soil tare data of crop processing factories and area and crop yield statistics. Until the middle of the 20th century, potato and roots and tubers grown as second crop, had the largest share in the SLCH-crop growing area in Belgium. Sugar beet gained importance from the end of the 19th century onwards and has now, of all SLCH crops, the largest growing area. We could estimate that, partly due to increasing crop yields and the mechanisation of the harvesting process, SLCH per hectare of cropland increased from 0.4 Mg ha⁻¹ year⁻¹ in 1846 to 2.4 Mg ha⁻¹ year⁻¹ in the 1970s and early 1980s. Since then mean annual soil losses decreased again to 1.8 Mg ha⁻¹ year⁻¹ in 2004. It was assessed that total yearly SLCH in Belgium rose from more than 575,000 Mg in the middle of the 19th century to more than 1.7 × 10⁶ Mg in the 1970s and early 1980s, while current SLCH values are 1.4 × 10⁶ Mg. We estimated that since 1846, more than 163 × 10⁶ Mg soil was exported from cropland in Belgium through this erosion process, which corresponds to 109 hm³ or an average soil profile truncation of 1.15 cm. Average sediment export from cropland in Flanders was 3.7 Mg ha⁻¹ year⁻¹ in 2002, of which 46% was due to SLCH and 54% was due to water erosion processes. The relative importance of SLCH varied, depending on the agricultural region, between 38% and 94%.     

Airborne bioaerosols and their impact on human health

Bioaerosols consist of aerosols originated biologically such as metabolites, toxins, or fragments of microorganisms that are present ubiquitously in the environment. International interests in bioaerosols have increased rapidly to broaden the pool of knowledge on their identification,quantification, distribution, and health impacts(e.g., infectious and respiratory diseases,allergies, and cancer). However, risk assessment of bioaerosols based on conventional culture methods has been hampered further by several factors such as:(1) the complexity of microorganisms or derivatives to be investigated;(2) the purpose, techniques, and locations of sampling; and(3) the lack of valid quantitative criteria(e.g., exposure standards and dose/effect relationships). Although exposure to some microbes is considered to be beneficial for health,more research is needed to properly assess their potential health hazards including inter-individual susceptibility, interactions with non-biological agents, and many proven/unproven health effects(e.g., atopy and atopic diseases).     

An economic assessment of the health effects and crop yield losses caused by air pollution in mainland China

Air pollution is severe in China, and pollutants such as PM_(2.5) and surface O_3 may cause major damage to human health and crops, respectively. Few studies have considered the health effects of PM_(2.5) or the loss of crop yields due to surface O_3 using model-simulated air pollution data in China. We used gridded outputs from the WRF-Chem model, high resolution population data, and crop yield data to evaluate the effects on human health and crop yield in mainland China. Our results showed that outdoor PM_(2.5) pollution was responsible for 1.70–1.99 million cases of all-cause mortality in 2006. The economic costs of these health effects were estimated to be 151.1–176.9 billion USD, of which 90% were attributed to mortality. The estimated crop yield losses for wheat, rice, maize, and soybean were approximately 9, 4.6, 0.44, and 0.34 million tons, respectively, resulting in economic losses of 3.4 billion USD. The total economic losses due to ambient air pollution were estimated to be 154.5–180.3 billion USD, accounting for approximately 5.7%–6.6% of the total GDP of China in 2006. Our results show that both population health and staple crop yields in China have been significantly affected by exposure to air pollution. Measures should be taken to reduce emissions, improve air quality, and mitigate the economic loss.     

Atmospheric dry deposition flux of metallic species to the North Sea

Air sampling on a series of 10 research cruises on the North Sea (south of 56°N) has yielded detailed spatial distributions of atmospheric metal concentrations, Al, Ca, Cd, Cu, Fe, Mg, Na, Pb and Zn which closely parallel the results of earlier published models. Air mass back trajectory analysis demonstrates the strong influence which source region may have upon the elemental composition of the North Sea atmosphere. A cascade impactor designed to collect efficiently large as well as small aerosol has produced detailed size distributions from which mass weighted deposition velocity estimates have been produced (Al, 0.33; Cd, 0.24; Cu, 0.44; Fe, 0.30; Pb, 0.13; Zn, 0.30 cm s⁻¹) enabling estimates for the dry deposition flux to the study area to be made. Extrapolation of these data to the whole of the North Sea yields dry deposition flux estimates (Cd, 33; Cu, 350; Pb, 370; Zn, 2640 tonnes yr⁻¹) which are in some instances substantially lower than those previously reported, but nevertheless represent a significant pathway for metallic species to enter this marine environment. The size distributions show the clear dominance that large aerosol has upon the overall dry deposition flux. Flux estimates are thus highly sensitive to the sampling of this large aerosol component, and to assumptions made regarding the sea surface as a source of giant trace metal-enriched particles which act only as a means of recycling marine metals.     

单体滑坡灾害危险性评价方法研究

滑坡是我国山区城镇建设中危害较大的一种地质灾害,本文在综合分析国内外危险性评价方法的基础上,结合实例分析,提出了适用于单体滑坡的危险性评价。即根据蒙特卡洛法的基本原理及方法编制了滑坡的稳定性可靠度分析程序,计算不同工况下滑坡失稳的概率。同时,利用离散元软件模拟滑坡运动过程,进一步确定滑坡影响范围。危险性评价的结果可为滑...     

Impacts of Global Climate Change on Mediterranean Agrigulture: Current Methodologies and Future Directions. An Introductory Essay

Current trends in Mediterranean agriculture reveal differences between the Northern and Southern Mediterranean countries as related to population growth, land and water use, and food supply and demand. The changes in temperature and precipitation predicted by general circulation models for the Mediterranean region will affect water availability and resource management, critically shaping the patterns of future crop production. Three companion papers analyze in detail future impacts of predicted climate change on wheat (Triticum aestivum L.) and maize (Zea mays L.) production in Spain, Greece, and Egypt, and test farm- level adaptation strategies such as early planting and cultivar change with the aid of dynamic crop models. Strategies to improve the assessment of the potential effects of future climate change on agricultural production are discussed.     

Impact of Climate Change on Possible Scenarios for Egyptian Agriculture in the Future

If no timely measures are taken to adapt Egyptian agriculture to possible climate warming, the effects may be negative and serious. Egypt appears to be particularly vulnerable to climate change because of its dependence on the Nile River as the primary water source, its large traditional agricultural base, and its long coastline, already undergoing both intensifying development and erosion. A simulation study characterized potential yield and water use efficiency decreases on two reference crops in the main agricultural regions with possible future climatic variation, even when the beneficial effects of increased CO₂ were taken into account. On-farm adaptation techniques which imply no additional cost to the agricultural system, did not compensate for the yield losses with the warmer climate or improve the crop water-use efficiency. Economic adjustments such as the improvement of the overall water-use efficiency of the agricultural system, soil drainage and conservation, land management, and crop alternatives are essential. If appropriate measures are taken, negative effects of climate change in agricultural production and other major resource sectors (water and land) may be lessened. This revised version was published online in August 2006 with corrections to the Cover Date.     

区域滑坡地质灾害危险性评价与风险管理

<正>随着社会经济的飞速发展,人类生存空间不断向山区扩展,使得近年滑坡等山地灾害的发生越来越频繁,人们越来越认识到防范和减轻滑坡等地质灾害对社会经济发展的重要性,迫切需要寻求对滑坡地质灾害进行更为有效地控制和管理的现实途径。而区域滑坡地质灾害危险性评价是滑坡地质灾害风险评价和风险管理的基础,本文在这一领域做了有益的探讨,取得了以下主要成果: