how does the compuer system of irrigation pumps work?

Answer 1

Well this is a wild guess, but you could have a system designed to use the water efficiently and optimize production. It might be a small "embedded system" based on a "microcontroller" chip (aka integrated circuit). The chip would read sensors measuring weather and soil conditions, and/or download and upload weather data from a network. (By the way, all of this could be done fairly inexpensively.) One example of a sensor is a plaster block (Calcium Sulfate, CaSO4) in the soil. The electrical impedance of the plaster changes with water tension, and is easily measured by an RC oscillator. If the soil gets too dry, it would switch on a pump, etc.

Another, even fancier way would be to program the chip with an equation that models evapotranspiration. http://en.wikipedia.org/wiki/Evapotranspiration
...such as the Penman equation, or the Penman-Monteith variation recommended by the Food and Agriculture Organization. http://en.wikipedia.org/wiki/Penman_equation
The data for the calculation could come from sensors or a weather station. Then the pump would be turned on as needed to replenish soil moisture.

Simpler methods would be a float switch on the pump, like the one in a toilet, to keep a constant water level.

Simpler yet, Farmer Jon just pumps water when he feels like it.

Obviously there are trade-offs to each approach, so the best approach depends on the application.

Answer 2

It works however you set it up to work.