The model AGRPRICE illustrates economic use of agricultural production (Figure IV-7).

Rather than have two prices, one for sales and one for goods and services purchased (as in ECONOMIC USE), this model has relative price (P) which is proportional to the availability of goods and services (F) and to quantity of crop produced (C). In this way details of money flow are omitted.

In agricultural systems, goods, like hoes or tractors, and farm workers are needed to produce the crop. These are labeled "A, Farm assets." As the crops (C) are growing more abundant, the price (P) you can sell them for goes down inversely. The price is also dependent on the availability (F) of goods and services in the world markets. When world resources are cheap their availability is large (the lower the price, the higher the availability), which means the price you can get for the crop tends to be high.

In the simulation (Figure IV-7b), outside availability of goods and services is held constant and low as in a time of low world resources. The run starts without much farm assets. At first crops are small and prices high, but as assets build up, a steady state develops with lower prices.

Examples of Agricultural Models

This model fits any farm, fishery or forestry production which uses a combination of nature and outside goods and services to produce the crop for sale.

Prices received for agricultural goods produced on a large scale almost always depend both on the amount of crop produced and the cost of necessary goods and services. In the citrus industry quantity of crop produced can affect prices received for oranges: the larger the crop, the lower the price. And, the price the industry charges is also affected by the availability of goods and services needed.

This model could represent a small farmer too, who sells vegetables on the side of the road. When tomatoes are abundant and easily available, he must sell them more cheaply than when they become scarce.

"What If" Experimental Problems

1. How would assets, crop and price be different if the enterprise starts with more available goods and services? Start with F = 4 instead of 2.
   


2. What would happen if availability of goods and services were decreasing each year? Set K7 = 0.01 and rerun.
   


3. What would be affected if the environmental inputs (I0) were 80% due to a drought?

COMPUTER MINIMODELS AND SIMULATION EXERCISES FOR SCIENCE AND SOCIAL STUDIES

Howard T. Odum* and Elisabeth C. Odum+
* Dept. of Environmental Engineering Sciences, UF
+ Santa Fe Community College, Gainesville

Center for Environmental Policy, 424 Black Hall
University of Florida, Gainesville, FL, 32611
Copyright 1994

Autorização concedida gentilmente pelos autores para publicação na Internet
Laboratório de Engenharia Ecológica e Informática Aplicada - LEIA - Unicamp
Enrique Ortega
Mileine Furlanetti de Lima Zanghetin
Campinas, SP, 20 de julho de 2007