Use Of Tractors Research Articles

On the Indirect Effect of Biofuel

American Journal of Agricultural Economics Advance Access published June 24, 2013 O N THE I NDIRECT E FFECT OF B IOFUEL D AVID Z ILBERMAN , G EOFF B ARROWS , G AL H OCHMAN , AND D EEPAK R AJAGOPAL David Zilberman (zilber11@berkeley.edu) is a Professor and Robinson Chair in the Agricultural and Resource Economics Department at UC Berkeley and a member of the Giannini Foun- dation. Geoff Barrows (geoffrey.barrows@gmail.com) is a GSR (Graduate Student Researcher) in the Department of Agricul- tural and Resource Economics at UC Berkeley. Gal Hochman (hochman@AESOP.Rutgers.edu) is an Associate Professor at Rut- gers University. Deepak Rajagopal (rdeepak@ioes.ucla.edu) is an Assistant Professor at UCLA. This research was supported by the Energy Biosciences Institute. We would like to thank Scott Kaplan and Eunice Kim for their invaluable assistance. This article was presented in an invited paper session at the 2013 ASSA annual meeting in San Diego, CA. The articles in these sessions are not subjected to the journal’s standard refereeing process. Economists have found that LCA has multi- ple flaws (Khanna and Crago 2012) in current biofuel polices and many have reservations about the use of LCA as a major regulatory tool. But accepting that LCA is used for regu- lation,our challenge is to use economic analysis to evaluate the use of ILUC in computing the GHGE of biofuel in the policy process. In the next section we develop an economic foundation for the computation of ILUC and derive a related indirect effect—the indirect food consumption effect (IFCE) of biofuels. This is followed by the discussion of other indi- rect effects. The third segment investigates the reliability of ILUC estimates and their use in the regulatory process, which is followed by a conclusion. Conceptual Analysis of the Use of LCA in Computing GHGE of Biofuels To better view the LCA of GHGE of bio- fuel from an economic perspective, we will develop a simple conceptual model. Let B denote the amount of a biofuel we analyze. LCA considers the GHGE resulting from the production of B units of biofuel throughout the supply chain. Assume that biofuel production includes two stages: production of feedstock and processing used to produce the biofuel. The GHGE generated in producing the biofuel can be decomposed into (1) the emissions from the production of the feedstock denoted by GF and (2) emissions from processing denoted by GP. The calculation of the GHGE of the feedstock GF considers the GHGE of activ- ities both on the farm (use of tractors and other machinery) and off the farm (produc- tion of fertilizers). LCA is seeking to calculate impact coefficients based on average perfor- mance that will enable the assessment of the annual GHGE associated with a proposed Amer. J. Agr. Econ. 1–6; doi: 10.1093/ajae/aat038 © The Author (2013). Published by Oxford University Press on behalf of the Agricultural and Applied Economics Association. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com Downloaded from http://ajae.oxfordjournals.org/ at University of California, Los Angeles on August 22, 2014 Biofuel policies were partially motivated by concerns about climate change. Therefore, qualifications for the benefit of these poli- cies were based on the amount of green- house gas emissions (GHGE) of particular biofuels. For example, entitlement for subsi- dies and mandates associated with the U.S. Energy Independence and Security Act of 2007 requires remaining below upper bounds of GHGE per gallon. The computation of the GHGE of biofuel are based on lifecycle analy- sis (LCA), which takes into account emissions throughout the supply chain, including fertil- izer production and use, shipping, and refining. Searchinger et al. (2008) introduced the indi- rect land use change (ILUC) of biofuel pro- duction, which is the extra GHGE resulting from the expansion of acreage of a feedstock such as corn to accommodate the increase in price associated with the introduction of bio- fuel. Governments have considered including ILUC in computing GHGE of various biofu- els to determine compliance with policies like the Renewable Fuels Standard (RFS) or Low Carbon Fuel Standard (LCFS). Thus, inclusion of the ILUC in the computation GHGE of a fuel will make it more difficult to qualify for the RFS. This paper identifies some of the chal- lenges associated with the application of LCA, and in particular, the use of ILUC as part of the estimated GHGE of biofuel.

Analysis of the effects of Zimbabwean white farmers on small scale farming in Nigeria

Many observers believe that the on-going liberalization of the world will have dramatic negative effects on small farmers in both developed and developing countries. This study aims to capture the effects of the presence of foreign migrant farmers on small scale farm­ing systems, which are prevalent in Nigeria. The Agricultural Development Project Zone D in which the white farmers settled in the state of Kwara, was used as a case study. Primary data were collected from white farmers as well as from local farmers regarding their situ­ation before and after the arrival of white farmers. Descriptive statistics and analysis of the farm budget were used in evaluating the data. The majority of local farmers (98.63%) transitioned towards sole cropping since the arrival of white farmers in the area. There were significant increases in seed rate, fertilizer and other chemicals, as well as labor inputs per farmer in the area when compared to the situation that was prevalent before the white farmers settled there. Their average farm size, distances between their houses and farms and tractor use reduced significantly, while output per farm size increased considerably since the arrival of white farmers in the area. In order to provide sustainability of the posi­tive development, there is the need to seek a policy option that will calm local farmers who once in a while exhibit signs of dissatisfaction for the way in which white farmers came to settle on their land. These could be achieved through the use of the participatory approach to agricultural development in the area. This approach could also be relevant in other re­gions of the world with similar situations.

Dynamics of process of braking of the wheeled tractor-analogue of “Belarus 3022 DV” with hydrostatic-mechanical transmission

Increasing volume of agricultural production is impossible without increase of the volume of transportation in this area. Wide range of goods transported, sharp fluctuations in demand for transport in the course of year are conditions for effective use of wheeled tractors in agriculture. At the same time, the increase of transport speeds of wheeled tractors and the emergence of new types of transmissions sharpen the problem of maintaining security in the braking mode. That is why there is an important problem in the study of braking of wheeled tractors with hydrovolumetric-mechanical transmissions. The article presents the spatial mathematical model of braking of a tractor-analogue Belarus 3022 DV with hydrovolumetric-mechanical transmission. The article shows the block diagram and the mathematical model of transmission of the tractor-analogue Belarus 3022 DV, as well as the physical and mathematical model of its braking. The presented spatial mathematical model of braking of the wheeled tractor-analogue Belarus 3022 DV with hydrovolumetric-mechanical transmission permits to investigate the influence of methods of service and emergency braking, brake system types and operating conditions on kinematic, force and energy parameters of hydrovolumetric-mechanical transmission and braking performance

Agricultural Mechanization in Ghana: Is Specialization in Agricultural Mechanization a Viable Business Model?

Since 2007, the government of Ghana has been providing subsidized agricultural machines to private enterprises established as Agricultural Mechanization Services Enterprise Centers (AMSEC) to scale up tractor-hire services to smallholder farmers. Although farmer’s demand for mechanization has increased in recent years, most of this demand concentrates on land preparation (plowing) service. Using the firm investment model and recent data, this paper quantitatively assesses whether AMSEC as a private enterprise is a viable business model attractive to private investors. Even though the intention of the government is to promote private sector-led mechanization, findings suggest that the AMSEC model is unlikely to be a profitable business model attractive to private investors even with the current level of subsidy. The low tractor utilization rate as a result of low operational scale is the most important constraint to the intertemporal profitability of tractor-hire services. Our findings further support the argument of Pingali, Bigot, and Binswanger (1987), who indicated that mechanization service centers supported through government’s heavy subsidy are not a policy option anywhere in the world, even in the current situation in Ghana. Although the tractor rental service market is a proper way of mechanizing agriculture in a smallholder-dominated agricultural economy such as Ghana, this paper concludes that the development of such a market depends crucially on a number of factors, including increased tractor use through migration across the two very different rainfall zones (north and south), increased tractor use through multiple tasks, and use of low-cost tractors. The government can play an important role in facilitating the development of a tractor service market; however, the successful development of such a market depends on the incentive and innovation of the private sector, including farmers who want to own tractors as part of their business portfolio, traders who know how to bring in affordable tractors and expand the market, and manufacturers in exporting countries who want to seek a long-term potential market opportunity in Ghana and in other west African countries.

Analysis of maize production and supply for food security improvement in the Borgou region in Northeast of Benin

The analysis of maize production and supply in Borgou region was conducted using data collected from 186 producers of maize. The analysis was done by commonly using means comparison tests and a multiple regression model. It comes out from this analysis that only 20.44% of the production is self-consumed, against 79.56% supplied on the market. Also, when the maize cultivated areas increase by 1%, its supply raises by 0.15%. As well, the use of mineral fertilizer and plough and/or tractor induces an increase by 65.86% in the supplied quantity. In contrast, the difficulties of access to production factors have a negative impact on the maize supply and the producers who are men supply 35.4% of maize quantity less than the women. Thereby, it is important that agricultural policies focus on easing access to production factors to widen the cultivated areas for more maize quantity to be supplied. Key words: Production, supply, maize, regression, Borgou.

TRANSGENIC VEGETABLES FOR 21ST CENTURY HORTICULTURE

Vegetables are grown worldwide and play an important role in human diets because they provide vitamins, minerals, dietary fiber, and phytochemicals. Vegetables are also associated with improvement of gastrointestinal health, good vision, and reduced risk of heart disease, stroke, chronic diseases such as diabetes, and some forms of cancer. The consumption and caloric contribution of vegetables to the diet vary widely with geographical region, nationality, local customs, and cuisine. Vegetable production suffers from many biotic stresses caused by pathogens, pests, and weeds and requires high amounts of plant protection products per hectare. US vegetables farmers are benefiting from growing transgenic squash cultivars resistant to Zucchini yellow mosaic virus, Watermelon mosaic virus, and Cucumber mosaic virus, which were deregulated and commercialized since the mid-1990s. Bt-sweet corn has also proven effective for control of some lepidopteran species and continues to be accepted in the fresh market in the United States, and Bt-fresh-market hybrids are released each year. Likewise, transgenic Bt-eggplant was bred to reduce pesticide use and hopefully will soon be grown by farmers in Asia. There are other vegetable crops in the pipeline that have been genetically modified to enhance their host plant resistance to insects and plant pathogens (including viruses), to show herbicide tolerance, and to improve features such as slow ripening that extends the shelf-life of the produce, high nutritional status, seedless fruit, and increased sweetness. Transgenic plant breeding therefore provides genetically enhanced seed embedded technology that contributes to integrated pest management in vegetable production by reducing pesticide sprays as well as improving food safety by minimizing pesticide residues. Furthermore, herbicide-tolerant transgenic crops can help reducing plough in fields, thereby saving fuel because of less tractor use, which also protects the structure of the soil by reducing its erosion. Transgenic vegetable crops could make important contributions to sustainable vegetable production in this 21st century. However, countries vary in their market standards of acceptance of transgenic crops. Biotechnology products will be successful if clear advantages and safety are demonstrated to both growers and consumers.

Factors influencing the use of alternative land cultivation technologies in Swaziland: Implications for smallholder farming on customary Swazi Nation Land

Poor land preparation and late planting are among the factors responsible for the decline in food production on customary Swazi Nation Land (SNL). While efforts are being made to develop an improved national land cultivation programme, this process can be helped by identifying factors that influence farmers to use alternative technologies for land cultivation. Using cross-section data collected in 2009 from a random sample of 210 farmers in Komati, three land cultivation technologies were identified; (i) use of tractors; (ii) use of draught animals; and (iii) use of hand hoes. For a country like Swaziland where human health problems, particularly HIV/AIDS, make manual labour a scarce resource, the use of tractors is regarded as a modern technology that can achieve time and labour savings. The empirical evidence from this study indicates that the use of tractors is significantly influenced by household wealth and size of arable land used by households. However, given that land holdings on customary land are generally small, sparsely distributed and often fragmented, tractor hire service providers face relatively high overhead and transaction costs. Furthermore, investment in mechanised farming by individual SNL households is constrained by the lack of secure tenure. Given these challenges, this study makes recommendations for creating an enabling environment that could promote the adoption of improved land cultivation methods by smallholders on customary SNL.

Resource use Efficiency in Wheat Cultivation Under Resource Conservation Technology (Rct) in Eastern U.P., India

The stagnation in yield growth may be the result of the degradation of resource base caused by mining of soil nutrients, declining organic matter levels, increasing salinity, depleting underground water table, buildup of weeds, pathogens and pest population. All these necessitated to think over sustainability of resources and conservation. The resource conserving technologies (RCTs) are in an emerging state all over the world. The study was conducted in Mirzapur district of Uttar Pradesh in the year 2011. Mirzapur district consists of 12 blocks. In four blocks RCTs were extensively adopted by the farmers, out of which, Jamalpur and Naryanpur blocks were randomly selected. Eight villages were selected from these blocks for the purpose of the study. A total 160 farmers (RCTs adopters 80 and non-adopters 80) were selected randomly. Costs and returns were estimated. Cobb-Douglas production function was used to measure resource use efficiency. The input use pattern of zero tillage and conventional tillage shows that zero tillage used fewer amounts (but some inputs like seed, irrigation used the costly) of many inputs in comparison to that of conventional tillage. The wheat grain yield obtained by adopters was significantly higher than that of nonadopters. The net returns and returns to cost ratio were also found to be higher, in case of adopters resource conserving technology. The value of the coefficient of multiple determination (R2) was found to be very high in case of adopters as well as non-adopters. The coefficient of elasticity of production (regression coefficient) attached to the variable human labour and tractor use turned out to be positive and significant incase of adopters and non-adopters whereas irrigation water and fertilizer were used excessively in case of adopters.

Mechanisation of Soya Bean Harvesting For Small and Medium Scale Farmers in Zimbabwe

The new land holdings and cropping enterprises after the Fast track land Reform Programme (FTLRP) in 2000 have created challenges with respect to the forms of field mechanization inputs needed by the new farmers to undertake timely and cost effective production and harvesting processes without proper mechanisation. Harvesting is a time critical operation for soya bean farmers in that if undertaken late, shattering results leading to high quantitative field losses. The paper presents current soya bean harvesting practices and their respective economic and operational challenges. The use of animal or single axle tractor as a power source to pull a ground driven cutter bar for cutting soyabean, manual gathering and using threshers showed that soya bean harvesting can be mechanised cost effectively for low yield (0.8t/ha) farmers. The system is 50 times faster than manual methods of harvesting. The system improves farmers' access to the services basic technologies are existing and are currently commercially available on the market. A maximum capital of US$4200 is required to set up the complete system compared to $US 334 000 initial investment required for a combine harvester. The harvesting costs can be maintained at less than 13% of the market value of the crop. The paper presents ownership options which optimize capacity utilization leading to cost effective solutions for soya bean harvesting amongst Zimbabwe's emerging soya bean farmers.

Dry direct-seeding of rice for mitigating greenhouse gas emission: field experimentation and simulation

Conventional puddled transplanted rice (TPR) is a major source of greenhouse gas (GHG), particularly methane, causing global warming. Direct-seeded rice (DSR) is a feasible alternative to mitigate methane emission, besides saving water and labor. A 2-year field experiment was carried out to quantify GHG mitigation and water- and labor-saving potentials of the DSR crop compared to TPR in three villages in Jalandhar district of Punjab, India. The InfoRCT simulation model was used to calculate the emission of CO2 besides CH4 and N2O in different districts of Punjab, India. Total global warming potential (GWP) in transplanted rice in various districts of Punjab ranged from 2.0 to 4.6 t CO2 eq. ha−1 and in the DSR it ranged from 1.3 to 2.9 t CO2 eq. ha−1. Extrapolation analysis showed that if the entire area under TPR in the state is converted to DSR, the GWP will be reduced by 33 %, and if 50 % area is converted to DSR the GWP will be reduced by 16.6 % of the current emission. The DSR crop saved 3–4 irrigations compared to the transplanted rice without any yield penalty. Human labor use also reduced to 45 % and tractor use to 58 % in the DSR compared to TPR.

Autonomous Perforating Tool Works Without Umbilicals and Self-Destructs During Process

This article, written by Editorial Manager Adam Wilson, contains highlights of paper SPE 147296, ’Autonomous Perforating System for Multizone Completions,’ by Pavlin B. Entchev, SPE, and Renzo Angeles, SPE, ExxonMobil Upstream Research Company; Krishnan Kumaran and Niranjan Subrahmanya, ExxonMobil Corporate Strategic Research; and Randy Tolman, SPE, RC Tolman, prepared for the 2011 SPE Annual Technical Conference and Exhibition, Denver, 30 October-2 November. The paper has not been peer reviewed. Autonomous downhole tools offer a range of advantages over conventional tools controlled manually through umbilicals. For instance, perforating guns or bridge plugs could be dropped or pumped downhole without the use of wireline, coiled tubing, or tractors. Because umbilical intervention is no longer required, the tools may perform an action automatically (e.g., perforate a desired interval), with substantial cost reduction and enhanced safety. An autonomous perforating system currently being developed is based on using a self-destructing disposable perforating tool that is run without a wireline. To accomplish this, the tool has three frangible components: a logging device, an onboard navigation system, and friable perforating guns. Introduction The autonomous system presented here enables individual stimulation of each zone in a multizone completion interval without the use of wireline or other conventional umbilicals. Because of such critical step elimination, the proposed system eliminates much of the crane work and lubricator exposure within the drilling footprint. More important, no additional wireline trips are required to change perforating-tool assemblies and pumping rate is no longer limited to the breaking strength of the cable. Fracturing operations can be continuous, as with the case of ball-actuated openhole technology, but with the additional advantage of being able to complete and treat individual zones as opposed to an entire range of perforation clusters that can lead to suboptimal stimulations. In addition, safety is improved by the reduction of equipment at surface, which could enable simultaneous operations such as completion while drilling, where wells are completed while the drilling rig continues to operate on the same pad. Thus, the system presented here has the potential to accelerate the production startup in pad development and improve the economics of the project. Objectives The overarching goal was to develop a prototype autonomous perforating system that meets and exceeds the current industry safety standards and requirements while using industry standard hardware such as perforating charges. With this goal in mind, the design of the autonomous perforating system should satisfy a number of specific objectives. One of the main objectives was to have a disposable tool that destroys itself downhole without obstructing future operations of the well. In addition, the system should not require any changes during the well-construction phase and should be usable in both newly drilled and previously drilled wells. This requirement eliminated several design possibilities, such as putting tags or markers in specific casing points.

Exposure Assessment of Tractor-Related Tasks Presenting Potential Overturn Hazards on Catfish Farms in Mississippi, USA

ABSTRACT Tractors are used in pond culture of catfish for a variety of mobile tasks, including placing aerators into ponds, mowing, spreading feed into ponds, and transporting equipment (e.g., seining reels), as well as for the stationary task of using the tractor's power-take-offs to operate aerators in the ponds. The mobile tasks place the tractor operator at risk of injury in the event of an overturn, and rollover protective structures (ROPS) are a proven intervention to mitigate injury in a tractor overturn. A 2008 survey was conducted among 96 participants in Mississippi (USA) to determine the hours of tractor use for these tasks. This article reports on exposures to tractor-related tasks conducted on catfish farms as identified in this survey. Annual exposure to potential tractor overturns was calculated based on the hours of mobile operation. The overall annual exposure to potential tractor overturns on the catfish farms participating in the survey was 7322 h per farm and 837 h per tractor on these farms. Findings show a prevalence of 88.2% of ROPS-equipped tractors on farms surveyed and a seasonal variation in exposure to each of the tasks, culminating in an annual estimate of exposure by task.

Determinants of Yield Gap in Lowland Rice Production in North-Central Nigeria.

Although Nigeria has comparative resource advantage in terms of favourable climatic, edaphic and ecological conditions in the production of rice, local production has not been able to meet the growing demand. The inability of the Nigerian rice economy to satisfy the domestic demand and the consequent growth of rice import quantity and value remains a cause of concern. The study analyzed the difference between potential and actual yield of rice in North Central Nigeria. Employing a multi-stage sampling technique, data were obtained through the use of structured questionnaire administered to a sample of one hundred and forty four rice farmers in Niger state, Nigeria. Data were analyzed using descriptive statistics and regression models. Results indicated that rice farmers in the area cultivated four improved rice varieties WITA 4, FARO 15, FARO 35 and FARO 44 with average yield gaps of 1.48, 2.85, 3.03 and 3.20 tons per hectare respectively. This makes these rice varieties under-exploited as farmers operate at levels where they obtain an average of 49% of the potential yield. Factors which contribute to the reduction in the magnitude of rice yield gap include increase in the frequency of contacts between farmers and extension workers, increase in fertilizer use per hectare and higher intensity of tractor use. It was recommended that the yield potential of cultivated rice varieties should be fully exploited as a first option to meeting the current level of national rice demand because increased rice production towards the attainment of self-sufficiency may well hinge upon the ability of farmers to narrow the gap between current rice yields and yield potentials.Keywords: Lowland rice, Yield gap, Nigeria.

An alternative skidding technology to the current use of crawler tractors in Alpine logging operations

Abstract The study investigated the possibility of replacing aggressive crawler tractors used in Alpine logging operations with a new rubber-tired mini-skidder, in the same size and cost class. Replacement proved desirable in terms of environmental protection and labor safety, and offered substantial economic benefits. While it required a moderate additional initial investment, extraction cost was reduced between 30 and 50%. On the average skidding distance of 130 m, productivity was 3.2 and 4.1 m3 per scheduled machine hour, respectively for the crawler and the skidder. Depending on extraction distance, skidding cost ranged from 19 to 47 € m3 for the crawler, and from 13 to 23 € m3 for the skidder. A model was developed to estimate machine productivity, extraction cost, and energy use for both machines (conventional and innovative) under a variety of work conditions typical of non-industrial private forestry. This information can be used for operational costing, planning and optimization. It can also serve to measure energy savings obtained through machine replacement.

The Problem With Diesel

Diesel engine exhaust (DEE) is a complex mixture of substances characterized by polycyclic aromatic hydrocarbons (PAH) surrounding an elemental carbon core. Diesel engines have a wide range of industrial applications including on-road equipment (most heavy and medium duty trucks and buses use diesel engines) and off-road applications in the mining, rail, construction, distribution, and farming industries and in the military, including the use of diesel-powered heavy equipment, locomotives, forklift trucks, ships, tractors, and generators. In a recent review of the literature , the highest levels of elemental carbon were reported for enclosed underground work sites in mining and construction with intermediate levels for above-ground semi-enclosed work areas for workshop mechanics, dock workers, and fire station workers, and the lowest levels being reported for enclosed areas separated from the source such as drivers, train crew, parking attendants, vehicle testers, and utility service workers ( 1 ). A large body of epidemiological work has shown consistent associations between particulate matter in ambient air and several health outcomes including chronic bronchitis, ischemic heart disease, stroke, and respiratory infections and exacerbation of asthma. The effect of DEE from traffi c on people with preexisting disease has also been shown, for example, in the reduction of lung function resulting from a 2- hour walk by people with mild or moderate asthma down London’s busiest shopping street (Oxford Street), where only diesel- powered buses and taxis are permitted access, compared with a similar walk round Hyde Park ( 2 ). The possibility that DEE might cause cancer in humans has been raised since 1955 when it was demonstrated that the particulate fraction of DEE contained PAHs such as benzo(a)pyrene known by then to cause tumors in experimental animals ( 3 ). The gas phase includes carbon monoxide and nitrogen oxides, but it is the particulate phase of the exhaust that appears to be implicated as a lung carcinogen. An effect of DEE on bladder cancer is also plausible because metabolites of PAH present in DEE are concentrated in the urine and may interact with the urothelium of the bladder ( 4 ). In this issue of the Journal, two related articles ( 5 , 6 ) report results from studies of DEE in miners based on quantitative estimates of respirable elemental carbon (REC) and focusing on lung cancer. In the cohort study ( 5 ) , inclusion of co-exposures such as silica did not change the fi ndings substantially. In the case – control study ( 6 ) , adjustment was carried out for several potential confounders including smoking. A dose – response relationship was found with increasing exposure to REC in both the cohort and case – control studies but is particularly clear in the latter, where an interaction between smoking and DEE was also found. These studies in miners make an important contribution to the body of evidence about DEE and are timely given the forthcoming International Agency for Research on Cancer (IARC) monograph meeting this year at which the current IARC categorization of DEE as a group 2A (probable human) carcinogen ( 7 ) will be reconsidered. The issue of causality is fundamental when estimating and ranking burden of disease attributable to various exposures. A recent study estimating the burden of occupational cancer in Great Britain chose to include all IARC group 1 (defi nite) and 2A carcinogens ( 8 ). DEE emerged as one of the most important problems. For bladder cancer related to exposure to DEE, the estimated total attributable fraction for bladder cancer was 1.00% (95% confi dence interval [ CI ] = 0.17 to 2.03), with an estimated 47 (95% CI = 8 to 94) deaths in 2005 and 106 (95% CI = 18 to 214) cancer registrations in 2004; for lung cancer, the attributable fraction was 1.84% (95% CI = 0.00% to 3.37%), with 605 (95% CI = 272 to 1107) deaths and 695 (95% CI = 313 to 1269) cancer registrations. DEE was the sixth most important occupational carcinogen, contributing 8.1% of the deaths and 5.9% of the cancer registrations. The majority occurred in land transport as expected but also in the construction industry where nearly 500 000 workers were estimated to have been exposed to DEE over the 40-year risk exposure period before the year of estimation. As the authors point out in the mining studies published in this issue, the levels of exposure they have found are high compared with other studies. The median elemental carbon values in the Oxford Street study were 7.5 μ g/m 3 (range 3.9 – 16) compared with

A model for estimating labour requirements during timber harvesting in snowbreak stands

The study makes a comparative analysis of labour use during timber harvesting with winches attached to agricultural tractors in undamaged stands and in snowbreak stands. Initially a model was used to determine the indicators of increased labour needed for stand maintenance following disturbance of the stand compared to a planned harvest. The model included the dependence of timber harvesting labour use on cut intensity and the length of each period of work during the typical working day in the undamaged stands, both in undamaged stands, and in snowbreak stands, a large proportion of working time was spent loading the vehicle and driving during loading of the vehicle. The average time period spent driving timber in both stand types was similar, but they differed in the allocation of labour. In undamaged stands most time was dedicated to use of agricultural tractors to harvest timber, whereas in damaged stands most time went on loading timber. Estimates of work consumption in snowbreak stands can consequently be measured in the same way as standard cultivated stands, however values should be increased by 227% in snowbreak stands to compensate for the differences in the load formation time.

Processing and utilization of coconut wood in Kerala

The coconut palm (Cocos nucifera L.) is the “tree of life” and known as “porcupine wood”. All parts of the coconut wood can be manufactured into commercial products. The wood is hard and durable; volumetric shrinkages are mostly smaller. The tree is non-branching and free of knots and can be used as decorative wood. No distinguishable separation between sapwood and heartwood. The logs are cut into 4–6 m length depending on height and soundness of the tree. Most efficient and least expensive system of log extraction is the use of agricultural tractor with a towing bar fitted to the hydraulic lift arms. Loading may be done by manually and by cross hauling with a skidding tractor or with a hydraulic front-end loader. Timber should be graded as hard, intermediate or soft corresponding to high, medium and low densities. Coconut wood is used in construction, furniture, high-value products, charcoal, chemicals, pulp and paper. Coconut wood utilization can supplement the supply of raw materials for the wood industry and provide low-cost and durable construction materials for housing programmes in the state and for export. Due to the low price of coconut wood, it becomes popular among the middle and low-income groups, and used as a substitute for commercially known wood species to overcome the inadequate supply of logs and help to conserve the remaining forests in Kerala.

Population and agriculture in the dry and derived savannah zones of Ghana

This paper examines the role of population in agricultural practices in food crop production in Ghana. Perspectives from Malthus and Boserup (land use extensification and intensification) and multiphasic response theory are drawn upon to postulate linkages between population and these two forms of response in land use. Data from a 2001 household survey of 504 households in 24 rural localities in two ecologically, climatologically, and culturally different regions of Ghana, viz, the dry and derived savannahs are drawn upon in this study. Descriptive statistics, correlation matrices, and multiple regression are used to explore relationships between population and land use in each region and together. Results show that both agricultural extensification and intensification are common in the derived savannah compared with the dry savannah, and that this is at least partly attributable to the former being characterized by better soils, larger farms, better access to agricultural and non-agricultural economic activities, and more schooling. While there was no evidence of Malthusian impacts on land extensification, this could result from the lack of available unused land. Boserupian intensification was evident in household size linkages with the intensity of labor use. There is also evidence of the theoretically proposed tradeoffs (hypothesized in multiphasic response theory) between extensification and intensification in the derived savannah and the two areas combined, between more land and lower labor intensity and between more tractor use and shorter fallow periods. The paper concludes with important caveats and suggestions for future research, as well as some policy implications for Ghana.

Solving a real-world vehicle routing problem with multiple use of tractors and trailers and EU-regulations for drivers arising in air cargo road feeder services

In this paper we present two approaches for solving a real-world vehicle routing problem arising in the air cargo road feeder service business. The problem is to combine transportation tasks from a given timetable to trips which have to be assigned to tractors and which can be operated by tractor drivers respecting the restrictive rules on driving times from EC Regulation No. 561/2006. Tractor trips which start and end at the hub can be combined to multiple-trips which are operated by the same tractor. Also, to each trip a trailer has to be assigned which is compatible with all tasks in the trip. The primary objective is to minimize the number of required tractors, i.e. the number of multiple-trips. The methods developed are currently applied in practice.

INSPEÇÃO TÉCNICA DE TRATORES E PULVERIZADORES UTILIZADOS EM PULVERIZAÇÃO AGRÍCOLA

Os projetos de inspeção de tratores e pulverizadores são realizados já a longo tempo. Estes projetos buscam obter informações sobre a qualidade dos equipamentos em uso nas pulverizações agrícolas. As inspeções fundamentam-se na necessidade de que aplicações sejam eficientes evitando contaminações desnecessárias do ambiente, seres humanos e animais. Objetivou-se com este trabalho, realizar inspeção e levantar informações sobre o estado de conservação dos pulverizadores e tratores na Depressão Central do Estado do Rio Grande do Sul. Durante a inspeção, foram avaliados os itens: manômetros, depósito de calda, filtros, bicos de pulverização, itens de proteção e segurança e verificações sobre o trator. Houve classificação das máquinas em aprovação, reprovação parcial ou reprovação. Foram inspecionados 84 pulverizadores e 75 tratores. Apenas 4 pulverizadores (4,8 %) foram aprovados, sendo a principal causa de reprovação, o tempo de uso. Os pulverizadores autopropropelidos tiveram maior aprovação. A metodologia foi eficiente, permitindo inspeção rápida e abrangente.