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The Mathematics of Reducing Drift: Part 1
by Lars Skjoldager Sorensen
Everyone wants to increase their spray efficiency. Spray efficiency reduces costs, combats pests more effectively and improves your relations with your neighbors.
Rainbow Ag wants you to understand the factors that can affect this efficiency. We call it "the spray account." The spray account is a simple formula for evaluating where your spray is going. Once you understand it, you can begin to focus your efforts to increase your efficiency.
The Spray Account
A number of factors make up the spray account. You can think of it as an equation:
Total amount of pesticide used =
On Target + Evaporation + Airborne Drift + Ground Loss
If the total amount of pesticide you apply remains constant, you can see that affecting one factor on the other side of the equation will simultaneously affect at least one other factor in the equation. Obviously, your goal is to increase on-target pesticide application.
Here's a very simple example of the spray account equation:
If you spray on a windy day and observe excessive airborne drift of your pesticide, you will necessarily decrease the amount of spray hitting your target. You've increased the "airborne drift" factor, and simultaneously decreased the on-target factor.
If, on the other hand, you can find a way to reduce airborne drift, you will automatically increase your on-target spraying, provided you aren't increasing either evaporation rates or ground loss!
Perhaps you can now see how useful the spray account equation could be when you are assessing your pesticide applications procedures.
Methods of Reducing Drift
The following methods have been documented to significantly reduce drift under most spraying conditions and in most types of crops.
- Increase droplet size.
- Direct spray to the intended part of the canopy.
- Where possible use a downward trajectory for drops.
- Match fan performance to crop and forward speed.
- Do not spray when turning out of the row.
- Avoid spraying under less than optimal weather conditions.
• To read Part 2 of Lars' article, click here.
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