Variable Rate Spraying

Variable rate spray application is receiving a lot or attention with our increased ability to farm according to prescription maps.  For dry products such as seed or fertilizer, metering is relatively straight-forward and variable rate application has been possible for many years. However, liquid product application has been more complex and requires special approaches Hydraulic […]

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Crop-Adapted Spraying (CAS) and an Apple Orchard Case Study

The ultimate goal of CAS is to adapt the amount of active ingredient per unit ground area such that the amount of active ingredient per unit target area (usually the leaf area) remains constant for canopies of varying shape and density. When this is achieved with sufficient accuracy, the pesticide efficacy is maintained. These three plants are all significantly different in size. When calibration is appropriate to each plant, the foliar coverage “experienced” for each plant will be the same, in spite of differences in the amount of solution expelled per ground area.

An orchard spraying scenario Here’s a common situation: An orchardist following IPM identifies a pest that poses an economic threat. It’s an annual pest and spraying is really a matter of when, not if. The operation is 150 acres and runs three airblast sprayers; two have a tower and one does not. Multiple varieties are […]

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Perspective on rates, volumes and coverage

This short article is a thought exercise designed to give some perspective on chemical rates, carrier volumes and the foliar area we expect them to protect. Imagine we are spraying the fungicide Captan on highbush blueberry. In Canada, the label rate is to apply 2kg/ha (28.5oz/ac) of planted area. Captan is 80% active ingredient, so […]

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Rate controllers on air-assist sprayers

There are many advantages to using rate controllers, but their primary role is to maintain a constant application rate. All sprayers change speed on hills, at row-ends, or in response to surface conditions. Since flow from an uncontrolled sprayer is constant, the application rate varies significantly (up to 40% in hilly conditions). Rate controllers compensate […]

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How to use Airblast Nozzle Tables

The author looking up nozzle rates during a spring calibration. The operator was running at 190 psi, but the catalogue only listed 180 psi and 200 psi. When span is only 20 psi, it’s fairly safe to approximate the output. When the table only lists in 50 psi increments, it is more difficult to determine the rate without testing the output. This issue usually occurs at pressures above 200 psi, and that’s very high for most horticultural operations. Consider using a lower operating pressure, if possible.

Airblast operators should know how to read a nozzle table. They are found on dealer and manufacturer websites as well as in their catalogs. Table layout varies with brand, but they all relate a nozzle’s flow rate to operating pressure. The better tables also provide the spray angle and the median droplet size (i.e. spray […]

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