Concept Of Economic Threshold Research Articles

Computational Linguistic Assessment of Textbooks and Online Texts by Means of Threshold Concepts in Economics

The ongoing digitalization of educational resources and the use of the internet lead to a steady increase of potentially available learning media. However, many of the media which are used for educational purposes have not been designed specifically for teaching and learning. Usually, linguistic criteria of readability and comprehensibility as well as content-related criteria are used independently to assess and compare the quality of educational media. This also holds true for educational media used in economics. This article aims to improve the analysis of textual learning media used in economic education by drawing on threshold concepts. Threshold concepts are key terms in knowledge acquisition within a domain. From a linguistic perspective, however, threshold concepts are instances of specialized vocabularies, exhibiting particular linguistic features. In three kinds of (German) resources, namely in textbooks, in newspapers, and on Wikipedia, we investigate the distributive profiles of 63 threshold concepts identified in economics education (which have been collected from threshold concept research). We looked at the threshold concepts' frequency distribution, their compound distribution, and their network structure within the three kinds of resources. The two main findings of our analysis show that firstly, the three kinds of resources can indeed be distinguished in terms of their threshold concepts' profiles. Secondly, Wikipedia definitely shows stronger associative connections between economic threshold concepts than the other sources. We discuss the findings in relation to adequate media use for teaching and learning—not only in economic education.

Economic threshold concept for weed management in crops: Usefulness and limitation

The economic threshold (ET) is one of the major decision-making frameworks for rationalizing herbicides use for better weed management while reducing environmental impacts. The ET is the density of weeds at which the cost of control equals the benefits obtained under particular weed control measure adopted. The ET rejects complete eradication of weeds, but advocates regulating weed populations at economically optimum levels. Control measure is adopted only when weed competition goes beyond a certain limit, thus, it uses certain damage levels for making cost-efficient weed management decisions. Several decision-making models on ET are available with high to low degree of precision. Despite potentials, the adoption of ET models as the major criterion for cost-effective herbicide use has been low. Limitations are building up of seed bank by residual weeds, complexity in estimating ET density, patchy weed distribution, and limited validity in cropping systems with multiple weed species. Yet, the ET-based decision has great potential in designing weed management under single weed dominance in crops. Information on weeds population dynamics in cropping system, biology, ecology and spatial heterogeneity would make determination of ET more precise and reliable, and managing weeds using integrated approach more successful.

Life table and economic threshold concept for ecologically sustainable management of Diacrisia casignetum Kollar (Lepidoptera: Arctiidae) on Jute

Life table and economic threshold (ET) level of Diacrisia casignetum Kollar on jute was calculated in West Bengal condition during 2016-2018 for environmentally benign management and better production of jute. The demographic data of D. casignetum always construct type-III survivorship curve like most of the insects. Potential fecundity (Pf) and total fertility rate (Fx) were 384.667±5.487 and 30893.60±1063.586, respectively. The average intrinsic rate of natural increase (rm) and the daily finite rate of increase (ë) were 0.106±0.001 and 1.111±0.003 respectively with the generation time (Tc) of 41.520±0.069 and doubling time (DT) of 6.563±0.021 days. Their mean population momentum factor of increase (PMF) was 19.676±0.605 including vital index (VI) and trend index (TI) of 0.522±0.003 and 92.359±2.648, respectively with different levels of significance. The economic injury level (EIL) and ET based on percent yield loss of jute were 7.119±2.166 and 6.385±1.969 pests per plant, respectively. At single pest observation per plant, the possible time taken to reach EIL (Ti) and ET (Tt) were 6.377±3.292 and 5.377±3.292 days, respectively which will be useful for better cultivation of jute and other subsequent crops.

Pesticide use in Indonesian vegetable farming and its determinants

PurposeThe purpose of this paper is to analyse factors affecting the use of pesticides in intensive vegetable farming in Java, Indonesia. Evaluating such factors is expected to provide appropriate policies to reduce pesticides, and eventually, mitigates the adverse impacts of pesticides on human health and the environment.Design/methodology/approachData were compiled from a farm survey of randomly selected 240 vegetable farmers in three regions of Java in 2014. A concept of economic threshold was employed to analyse the pesticide use determinants, which were estimated using econometric models.FindingsFactors leading to the increase in the application of pesticides were the number of observed insect pests, prices of vegetables, use of local varieties, and use of mixed pesticides. Conversely, factors lowering the use of pesticides were the number of observed diseases, the cost of pesticides, and area planted to vegetables. The most important factor in influencing pesticide use was farmers’ perception on the correct prediction of yield losses associated with pests and diseases.Research limitations/implicationsThe sample for this research is somewhat low and the analysis was based on one-year data of the quantity of pesticides in a formulation.Practical implicationsThe use of pesticides can be reduced by training farmers on crop protection practices, which provide correct information on pests and diseases. Policies related to the price of pesticides would be ineffective, as farmers still highly relied on pesticides. These findings will be useful for reducing the use of pesticides in intensive vegetable farming in Indonesia, and in tropical countries in general.Originality/valuePesticides have two opposite properties: to increase income on the one side and to cause devastation of life on the other side. Because pesticides are generally less selectively toxic than would be desired, non-targets including humans and the environment must be protected from contamination by these agrochemicals. This study found the most important determinants for reducing pesticide exposures in Indonesian intensive farming.

Фітосанітарний стан основних сільськогосподарських культур органічного виробництва України в умовах змін клімату

Climate change causes the environmental impacts on the population dynamics of insect pests, their distribution and feed. Under climate change it is especially important to assess the potential yield loss by complex of specialized pests of major organic crops in various regions of Ukraine. For increase of organic farming productivity it is necessary to improve affective control of plant pests using plant protection of organic crops. The results will also be a basis for recommendations of the best regions and the crop list for organic farming without increased risk of economic losses. The aim of the study was to determine the potential yield losses of crops for organic produce in regions of Ukraine under climate change. It was analyzed the data of pests distribution and their number in agrocenosis of Ukraine. Potential hazard of insect species was analyzed using the average economic indexes. For their calculations used ratio of actual pest quantity to the index of economic threshold of hazard. For calculation of indexes used the tables of threshold indexes of hazard of every species. The total pest damage (complex hazard) was determined by calculation the integral index of hazard. That is the sum of economic indexes of each species of harmful insect complex of crop with correction coefficient pointed out the features of plant response to damage of different pest species. Multiply index by 3% (minimal crop losses) allow estimating potential yield losses. If integrated economic index does not exceed 1, under the concept of economic threshold, crop protection against pests is not appropriate. In organic farming of Ukraine the winter wheat is a dominant cereal crop. The phytosanitary monitoring shown, that climate change had an effect on the hazard insect complex of wheat. In 1996-2004 the number of wheat fly has increased in pest complex of Forest Steppe. But a number of insects such as Hessian fly, wheat fly, corn-bug and opomyzid fly has decreased during recent years. During 2005-2011, a sharp increase of corn-bug number was recorded. But during next years, their population has decreased significantly. The transition to a state of corn-bug depression can be caused by rapid growth of cereals observed recently. By earlier harvesting a significant part of the corn-bug population does not have time to a normal physiological development and survival of the pest during the winter is reduced. Up to 2012, a number of corn ground beetles and corn bugs was more stable and varied from 0, 5 to 1, 6 individuals per square meter. In recent years the hot and dry weather and less precipitation in July – September has delayed output from diapause of corn ground beetles, decreased female fertility and caused death of eggs and larvae. The analysis allowed concluding that during the five-year period of 2011 to 2016 in conditions of climate warming a number of herbivores and the potential loss of yield of winter wheat - the main export cereal crop of organic produce of Ukraine - significantly decreased and upon the average did not exceed the threshold level. Thus, there were the favorable conditions for increase of winter wheat production using organic farming techniques without significant risk of economic losses from pests. There are risks of economic losses of organic produce of sunflower in the Vinnytsya, Kherson, Kharkov, Chernihiv, Donetsk and Kyiv regions; corn - in Kyiv, Ivano-Frankivsk, Vinnytsya, Donetsk, Luhansk, Kharkov regions; soya - in Lviv, Kharkov, Kherson, Kirovohrad, Volhynia, Vinnytsia, Ternopil, Kyiv, Dnepropetrovsk, Mykolaiv, Chernivtsi, Zaporizhzhya, Cherkasy, Rivne, Zakarpattia, Zhytomyr, Poltava regions. The organic farming of potato and cabbage requires a protection of plantations from the plant pests’ complex in all regions of Ukraine. To prevent economic losses from pests of organic crops in Ukraine the list of pesticides should check against standards of organic farming and should develop a search program of new biological agents of pest control. Keywords: climate change, organic farming, complex of plant pests, crop losses

Threshold concepts in economics

Purpose– The purpose of this paper is to examine threshold concepts in the context of teaching and learning first-year university economics. It outlines some of the arguments for using threshold concepts and provides examples using opportunity cost as an exemplar in economics.Design/methodology/approach– The paper provides an overview of the theoretical literature around threshold concepts in economics and provides exemplars from previous research, and current practice, to illustrate how they might be applied in economics.Findings– The notion of threshold concepts such as opportunity cost can be extremely useful in pedagogic design. They focus on how learning concepts changes student thinking, rather than the standard approach which treats many concepts as equal in importance. Designing appropriate instructional materials around threshold concepts is time consuming and this may prove a barrier to the notions widespread adoption.Originality/value– This paper contributes to the literature discussing the practical application of threshold concepts in teaching first-year economics as well as identifying possible reasons for its relatively slow adoption as a teaching tool in university.

Transforming the economics curriculum by integrating threshold concepts

Purpose– Economics is catering to a diverse student cohort. This cohort needs to be equipped with transformative concepts that students can integrate beyond university. When a curriculum is content-driven, threshold concepts are a useful tool in guiding curriculum re-design. The paper aims to discuss these issues.Design/methodology/approach– The evidence for this pedagogic need can be seen in the UK’s higher education economics curriculum framework which is formulated around the threshold concepts of economics. Through a literature review of the application of threshold concepts in economics, the researcher has systematically re-designed an entry-level economics course. This research has been applied to the course structure, the learning and teaching activities, as well as the assessments. At the end of the semester, students students were surveyed on the student experience of the curriculum design and the course activities. The course grades noted the achievement of the students’ learning outcomes.Findings– When comparing the survey responses and the student course results to the previous semesters, there is a significant improvement in student experience as well as student learning outcomes of the course curriculum.Practical implications– This research provides curriculum developers with a benchmark and the tools required to transform economics curricula.Social implications– An engaging, transformative and integrative entry-level economics course is often the only exposure most business graduates have to the economics way of thinking and practice.Originality/value– This is the first comprehensive study that applies a curriculum re-design based on threshold concepts across an entry-level economics course.

An Imagery-Based Weed Cover Threshold Established Using Expert Knowledge

The implementation of site-specific weed management requires information about weed cover and decision support systems to determine weed cover thresholds and concomitant herbicide rates. Although it is possible to create accurate weed cover maps over large areas, weed cover thresholds have generally been evaluated using tedious weed density counts. To bridge this gap between weed cover obtained by machine vision and the concept of economic threshold, crop advisers specializing in weed scouting were asked to evaluate over 2,500 weed cover images (2 m by 3 m) and determine if a given image would require herbicide application or not. Using the area under the “receiver operating characteristic” curve method, an optimal weed cover threshold was established. The derived economic thresholds ranged from 0.06 to 0.31% weed cover contingent on the level of tolerance of the expert adviser. Although this threshold seems low, it is comparable with economic threshold values based on weed density.

Threshold concepts and the integration of understanding in economics

This article outlines the recently developed idea of ‘Threshold Concepts’ and explains how this idea may be used to describe the progress of learning in economics. The authors examine the relationship between threshold concepts, key concepts and conceptual change and suggest that a distinction between basic, discipline and procedural concepts may be useful in determining a framework for the identification of threshold concepts. The current understanding of threshold concepts is extended by indicating that these might best be seen as a web of concepts which link thinking and practice in a discipline. A range of evidence is presented to illustrate the existence and implications of threshold concepts in economics.

Operationalising a Threshold Concept in Economics: A Pilot Study Using Multiple Choice Questions on Opportunity Cost

This paper addresses the emerging educational framework that envisions threshold concepts as mediators of learning outcomes. While the threshold concepts framework is highly appealing on a theoretical level, few researchers have attempted to measure threshold concept acquisition empirically. Achieving this would open a new arena for exploration and debate in the threshold concepts field, and provide potential results to inform teaching practice. We begin the process of operationalising threshold concepts in economics by attempting to measure students’ grasp of the threshold concept of opportunity cost in an introductory economics class. We suggest two potential measures and correlate them with an array of ex ante and ex post variables, including students’ expectations of success, prior misconceptions about economics and the work of economists, and actual success in the course. Results cast new light onto the factors that influence the acquisition of threshold concepts, the relationship between threshold concept acquisition and final learning outcomes, and the empirical viability of threshold concepts generally.

Field evaluation of regression equations to estimate crop yield losses due to weeds

Various regression equations based on weed density alone, or relative time of weed and crop emergence or crop density in addition to weed density have been developed in western Canada to estimate the effects of wild oat (Avena fatua L.) and volunteer cereals on yield loss of field crops, and to advise farmers on the economics of weed control with herbicides. In 1997, 1998, and 1999, several of these equations were evaluated in 9 barley (Hordeum vulgare L.), 9 wheat (Triticum aestivum L.) and 11 canola (Brassica napus L.) fields in Alberta. Wild oat was the dominant weed in the barley and wheat fields, and wild oat or volunteer cereals in the canola fields. In barley and wheat, more complex equations based on both weed density and either crop density or relative time of weed and crop emergence were more reliable in estimating yield losses due to wild oat than those based on weed density alone. In canola, an equation based on volunteer barley and canola density provided the most reliable estimates. Under the assumed crop prices and herbicide costs, these equations also resulted in the best estimates of whether or not a herbicide application resulted in a net profit or loss. Herbicide application was rarely economical in barley, but usually economical in wheat and canola reflecting the different market value of the crops. The implementation of the weed economic threshold concept is likely to be more feasible in low-value crops such as feed barley than in higher-value crops such as canola. Key words: Barley (Hordeum vulgare L.), canola (Brassica napus L.), volunteer cereals, weed economic threshold, wheat (Triticum aestivum L.), wild oat (Avena fatua L.)

Weed management decision models: pitfalls, perceptions, and possibilities of the economic threshold approach

The use of scouting and economic thresholds has not been accepted as readily for managing weeds as it has been for insects, but the economic threshold concept is the basis of most weed management decision models available to growers. A World Wide Web survey was conducted to investigate perceptions of weed science professionals regarding the value of these models. Over half of the 56 respondents were involved in model development or support, and 82% thought that decision models could be beneficial for managing weeds, although more as educational rather than as decision-making tools. Some respondents indicated that models are too simple because they do not include all factors that influence weed competition or all issues a grower considers when deciding how to manage weeds. Others stated that models are too complex because many users do not have time to obtain and enter the required information or are not necessary because growers use a zero threshold or because skilled decision makers can make better and quicker recommendations. Our view is that economic threshold–based models are, and will continue to be, valuable as a means of providing growers with the knowledge and experience of many experts for field-specific decisions. Weed management decision models must be evaluated from three perspectives: biological accuracy, quality of recommendations, and ease of use. Scientists developing and supporting decision models may have hindered wide-scale acceptance by overemphasizing the capacity to determine economic thresholds, and they need to explain more clearly to potential users the tasks for which models are and are not suitable. Future use depends on finding cost-effective methods to assess weed populations, demonstrating that models use results in better decision making, and finding stable, long-term funding for maintenance and support. New technologies, including herbicide-resistant crops, will likely increase rather than decrease the need for decision support.

Ecological Implications of Using Thresholds for Weed Management

Various types of thresholds have been developed for weed management in an attempt to provide a more rational approach to decision making. The economic threshold concept was originally developed for management of arthropod pests, and is based on an understanding of arthropod population biology. Adoption of a management strategy for weeds that was developed for maintaining arthropod populations below a damaging level, referred to as the economic injury level or EIL, is not ecologically sound. Many of the factors that regulate populations of the two types of pest are different. For arthropod management the economic threshold (ET) is defined as the pest population at which treatment should be initiated to stop the population from increasing to the EIL. Weed science has adopted the ET to be the same as the EIL; this leads to maintenance of a relatively high seed bank as weeds at or below the ET density are allowed to produce seed. Research where weed seed production was accurately determined in corn, sugarbeets, alfalfa and other crops is now suggesting that several important weed species should be managed so that they do not produce seed. I am proposing that a new threshold called a no seed threshold, or NST, should be established for such weeds. Application of the ET concept to an invading weed species is disastrous as it leads to establishment of the seedbank before any control action is taken; for an invading species that is expanding its range the use of NST seems more appropriate. Progressive farmers in California have adopted NST for management of weeds. These farmers claim that the strategy is economically superior to that using single season ET. In one case adoption of NST for weed management has resulted in decreased reliance on herbicides as weed control can be attained using non-chemical techniques. There is urgent need for weed science to develop improved data on weed population dynamics that is coupled to economics of weed control and crop production; until such data become available it is not feasible to accurately assess the use of thresholds for weed management.

THE REGIONAL ECONOMIC THRESHOLD FOR INTEGRATED PEST MANAGEMENT

The Regional Economic Threshold concept is introduced. A model of pest control decisionmaking is generalized to permit choice of materials, timing, number of applications, and dosage rates. Constraints on the maximum dose alter the model and solutions. An experiment is performed to generate data for estimating both the efficacy of insecticides and the damage prevented. Simulating nonlinear systems, a computer program calculates optimal solutions and the sensitivity of the solutions to various relative prices. Losses from legal maximum dosage constraints are calculated, as well as potential benefits to growers' profits from applying the results of this research.

Insecticide Use and Crop Rotation under Risk: Rootworm Control in Corn

AbstractThe economic threshold concept is extended to a combination of two pest controls, insecticide and crop rotation, in a corn‐soybean farm model. Effect of risk attitudes on the optimal combination of controls is explored, using a stochastic simulation with random crop prices, yields, and rootworn damage. Crop insurance may cause a risk‐averse farmer to adopt a riskier cropping program. Reduced risk aversion causes the farmer to specialize in the more profitable corn crop. The insecticide and rotation thresholds both increase with reduced risk aversion. Depending on pest densities on individual fields, insecticide use may increase or decrease.

Use of Computer Game Cotgame in Teaching Entomology 1

During the period 1977–1979, a computer assisted instructional tool known as COTGAME was used in teaching insect pest management at Mississippi State University. Computer models used in COTGAME simulate the interactions among a cotton crop and its main insect pests, predators, insecticide applications and weather. The game is divided into 3 phases: initialization, management and results. In the initialization phase, the user establishes the agronomic, weather and insect conditions for the game. During the management phase the user can select the next decision date, insecticide application, irrigation, fertilization or harvest. At each decision date a scouting report is provided. Once harvest is reached, the program produces a complete summary of the conditions set in the initialization phase, as well as the decisions and results which occurred during the simulated growing season. COTGAME has been used primarily to aid in the instruction of the economic threshold concept to both graduate and undergraduate students. In general, graduate students responded more positively to COTGAME than undergraduate students. The instructional value of COTGAME is discussed.

Pesticide Regulation: Economic, Biological, and Federal Viewpoints

Summary:The purpose of this symposium was to create an awareness of pesticide regulation research and not to discuss the positive and negative aspects of regulation. In this respect three topics of interest were discussed; federal, biological, and economic issues of regulation.Pesticide usage has been regulated in some form by the Federal Government since the 1930s. The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) of 1972 gave the Environmental Protection Agency (EPA) explicit authority to regulate these pesticides. The primary criterion for decision making under the statute is “unreasonable adverse effects on the environment” which is defined in FIFRA as “any unreasonable risk to man or the environment, taking into account the economic, social, and environmental costs and benefits of the use of any pesticide.”Once it is determined a pesticide does have adverse effects, then it enters the Rebuttable Presumption Against Registration (RPAR) process. The RPAR process determines the risks, costs, and benefits associated with the suspect chemical. This process is a coordinated effort between EPA, the United States Department of Agriculture, and the states. When the analysis is completed, the EPA administrator weighs the risks and benefits and determines whether regulatory action is required. Legal mitigation may then follow.Government regulation affects the discovery and development of pesticides and redirects research programs and production practices. Extensive regulation may encumber the research and development programs of chemical companies, increase the cost of chemicals reaching the market place, and decrease the number available to the producer, forcing him to revert to older or less effective chemicals. Both industry and producers must adapt to a constantly changing environment.On the other hand, regulating the use of chemicals may extend the life of a chemical because pest populations will be less apt to build up genetic resistance. Research programs may be redirected into areas of alternative pest control measures such as biological control and host plant resistance. This ultimately leads to integrated pest management strategies. Inherent in this redirection is the need for researchers and producers alike to understand the basic interactions of animals and plants which would spawn new non-chemical control measures and prompt more judicious use of chemical controls.EPA has tended to define benefits in a cost sense. In the economic analysis of pesticide regulation (primarily cancelling the registration of the pesticide) to date, benefits are synonymous with changes in production cost (per acre) for the affected producer and the industry (by commodity) as a whole. For this reason, the two methods of analysis have been partial budgeting and budgeting. There are two serious drawbacks in these approaches. Both problems originate from the short-run nature of the approaches. No supply response is considered in the analyses. This implies no consumer price effects and ignores the relevance of the concept of economic threshold in pesticide usage. Secondly, there has been little effort directed at regionalizing the producer impacts of the regulatory act. These problems must be overcome to perform adequate analysis. This requires increased research in the area pesticide productivity for supply response and regionalizing economic supply utilization, and price data.

AN OPTIMIZATION MODEL FOR LYGUS HESPERUS (HETEROPTERA: MIRIDAE) DAMAGE IN COTTON: THE ECONOMIC THRESHOLD REVISITED

AbstractThis paper presents results of a multidisciplinary optimization study on the impact of Lygus hesperus Knight on cotton in the Great Central Valley of California. The results of the empirical studies indicate that lygus bug is not a serious pest of cotton under most circumstances and, furthermore, illustrate why cotton yield enhancements have occurred when their populations have not been controlled. An economic analysis of these results sheds some light on the concept of economic threshold. In particular it is shown how in this case an economic threshold exists even if the costs of pesticides are zero. The theoretical implications of these results are quite general.