Tuesday, September 2, 2008

Chemigation using Center Pivot Irrigation machines

Chemigation is the application of agricultural chemicals such as pesticides or fertilizer with irrigation water. When used properly, chemigation is an environmentally sound and cost-effective way to apply many chemicals during the growing season. Safe and effective chemigation is accomplished by combining both good management and good equipment.
A very important part of management is accurate calibration. This fact sheet covers procedures for calibrating chemigation when using Center Pivot Irrigation Machines.
Chemigation calibration is the process of establishing how fast the center pivot will cover the field and adjusting the injection pump to apply the desired quantity of chemical per acre. Calibration insures that the proper amount of chemical is being applied thereby giving the highest economic gain and minimizing environmental risks.
Calibration is especially important when applying pesticides where specific label rates must be followed. The procedure for calibration is straight-forward, but it does involve a significant time commitment, an understanding of chemigation concepts, and basic mathematical skills. You will need to spend time and effort calibrating before any chemical is applied.
It is necessary that all parts of the irrigation and chemical injection system are operating properly. All chemigation safety equipment should be installed and operating (see FS 860 Chemigation Safety).
Always check the irrigation system for operating problems and uniformity of water distribution. Some older-style systems such as water drives may not have good water distribution because more water from the drive goes near the wheel track. Make sure that the nozzles are not worn and that all sprinklers are operating properly. Remember that the chemical can be applied only as uniformly as the water applied.
The irrigation system and the injection system must be calibrated. You need to know the following information when calibrating: acres covered, time to cover the field, depth of water applied, chemigation application rate, amount of chemical, injection rate.
Besides the chemigation equipment, other items to help with calibration include a stopwatch, calculator, long measuring tape, marking stakes or flags, and a calibration tube.

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