Ilan Amir

Analyzing agricultural demand for water with an optimizing model

Abstract The paper introduces an optimizing linear model for analysing agricultural production under various water quantities, qualities, timing, prices and pricing policies. The model is designed to serve as a decision-making tool for planners of agricultural production on district and national levels. The output solutions provide the optimal mix of water-consuming activities to maximize the net income of the agricultural production of the districts and the water demands under various prices. It also provides the user with procedures to carry out ‘if–then’ sensitivity and scenario analyses and to generate optimal water demand curves. The paper presents the formulation of the model, indicating and analysing problems of linearity and scaling, the steps undertaken to examine and verify it, optimal water demand curves for eight districts in Israel (separately and as an integrated unit) and calculated estimates of water demand elasticity.

Response of near-optimal agricultural production to water policies

Abstract The paper presents a study triggered by water policies, imposed by the Israel Water Commissioner on agriculture to cope with a shortage of water. Those policies were a combination of price policies and quantity restrictions. We analyze them for the case of the Jezreel Valley district, using a deterministic linear programming optimizing model. The optimal solution finds the mix of crops that maximizes the net income of the district. The results show that a mixture of policies to attain a single end is not efficient and can have unintended side effects. In particular, when water quotas are binding, raising water prices does not increase water productivity and merely places a tax on farmers. The response of Jerzreel Valley agricultural to water quota policy is affected significantly by the presence of unirrigated winter crops as an alternative to water-using crops. The model provides a useful decision-support tool for analyzing water policies.

ISFARM: An integrated system for farm management: Part I—Methodology

Abstract A comprehensive methodology that integrates algorithmic and nonprocedural methods is presented for the management of agricultural production at the farm level. An optimal plan is produced by a linear programming method along with its dual values and the post optimal sensitivity analysis. A monitoring process is continuously operated to collect data from the farm. Two expert system models evaluate, through a heuristic inference engine, the current value of each activity and the economic value of water and irrigation. Based on a comparison between the current values of the activities and resources and the plan, decisions are to be made whether to continue with the plan with or without tactical or operational changes or to carry out major strategic changes. In the latter case, a new linear programming model is run with updated values and with a new planning horizon. The methodology provides quantitative measures for the strategy of dynamic decision making.

Optimization with fuzzy constraints in agricultural production planning

Abstract Agricultural production systems are operated under severe uncertainty. One possibility in coping with the uncertainty in the decision-making process, is to create several plans for different expert assumptions of the unpredictable factors dominating the production, to evaluate the expected value of each plan and to select the largest one. This can be done by using linear programming (LP). In the suggested method, as in the above mentioned one, LP is used as the first stage of the decision-making process. However, in this method, we use the LPs post-optimal sensitivity analysis (POSA). POSAs insensitivity limits of the decision variables of the various solutions are used to create a set of two-sided non-equivalent inequalities. On the basis of this set and a fuzzy solution of a system of inequalities, fuzzy constraints are formulated. An algorithm to optimize a linear objective function with varied coefficients subjected to fuzzy constraints has been developed and is presented. The approach and the method are introduced and demonstrated using an unirrigated farm whose production is dominated by unpredictable rainfall. To evaluate the method, its production and the regular LP production plans were compared, with a significant advantage to the suggested method.

CROPLOT--An expert system for determining the suitability of crops to plots

Abstract CROPLOT is a rule-based expert system for determining the suitability of crops to given plots. Its use is in the process of plot allocation when planning the production of field crops on the individual farm, usually under severe uncertainties. CROPLOT takes into account specific factors of the plot, which are usually of a quantitative nature, and by a heuristic inference procedure suggests both verbal and numeric suitability coefficients for each crop. A comparison between recommendations of human experts and CROPLOT shows 90% agreement.

ISFARM—An integrated system for farm management: Applicability

Abstract A simulation of an application of ISFARM methodology is presented to demonstrate and to test the approach, the components and the applicability of the methodology of ISFARM. This methodology suggests the planning and operation of a farm by a sequential procedure that includes four stages: planning, monitoring, comparing between plan and execution, and decision making (whether to proceed with the current plan or to carry out an updated plan for a new planning horizon). These stages involve expert systems and linear programming models that are included in ISFARM. The case study is set on a 3-crop 100-ha farm in southern France. Following a scenario typical for the region, a decision-making process, based on the ISFARM methodology, is activated. The procedures of ISFARM methodology, the decision-making tools and measures, and the resulting planning and operating of the farm production show that ISFARM can be used to improve the decision-making process at a farm level, operating under severe uncertainty.

An Interactive Computerized Aid for the Design of Branching Irrigating Networks

ABSTRACT AN interactive, fast responding computer program for the design of new branching networks and for im-proving existing ones, is presented here. This program, which is based on the Linear Programming formulation, is aimed at finding the optimal economical combination of two main opposing factors: the cost of the investment and energy. This article contains the mathematical background, and by means of an example, the design procedure.

Biwinged excision for closure of rounded defect.

A new technique for closure of rounded defects is described. The biwinged procedure consists of excising two equal triangles on either side of the defect, one above and one below the dissecting line. Closure is in the form of a step. It can be made to parallel in part a wrinkle or contour line, such as a nasolabial fold, a temporal region above and beside the eyebrow, an area over the lower border of the mandible, or on the dorsum of the hand. A mathematical comparison of the amount of healthy tissue in the biwinged excision and in six other procedures is presented.

Monitoring and decision-making processes for operating agricultural production systems

Abstract Agricultural systems contain many inter-relationship factors which are uncertain or even unknown. Forecasting future situations is a difficult task under these uncertain conditions. Agricultural systems, however, are relatively flexible and can be adapted to new and unforeseen situations. Therefore, it is of importance to operate agricultural systems in such a way as to use their flexibility as a means of compensating for possible losses, and to take advantage of unforeseen events. One of the models which might be suitable for operating real agricultural systems under uncertainties is the Sequential Ad-hoc Linear Model. Detailed descriptions of two of the basic processes of this model, namely those of monitoring and decision making, are given in this paper. Examples taken from a real agricultural system are presented to demonstrate the application of the methodology.

Emitter Uniformity as an Economic Factor Trickle System Design

ABSTRACT The discharge uniformity of emitters in trickle irriga-tion is affected by several factors. A model based on net income and limiting land is used to analyze a simplified situation where the crop production function is known, and the only two sources of discharge variation are the manufacturing process and the hydraulic head variation. Based upon previous research, the variances of manufacturing and hydraulic variation are assumed to be additive. Therefore, the effect of the manufacturing variation is greatest when the hydraulic head variation is minimal. As is usually the case, it only pays to improve a component of the system when the other components are already at a higher standard. The results support a previous conclusion that the exact shape of the water distribution function is not important, and that the mean and the variance of the distribution are sufficient to characterize the distribution. An example is worked out to show how the optimal seasonal water application depth can be calculated. It is also shown how much it is justified to spend on improved emitters under certain circumstances.