With the widespread rains, many producers will not be able to make timely applications of fungicide to wheat using a ground rig. However this may not be the case in all areas. As producers evaluate their application options between ground vs. aerial application of fungicides they should keep several points in mind.
The IF and WHEN decisions of fungicide application are much more important considerations than the application method. Both application methods, when performed correctly under good conditions, provide effective application of fungicides. Always use the surfactants and solution rates as described on the product label for the chosen application method.
A common question from those considering ground rig application is the potential yield loss from wheel tracks. The table below shows the percent of field area that will be trafficked for various boom and tire widths.
|
|
Tire Track Width (inches) |
||
|
|
12 |
18 |
24 |
|
Boom Width (feet) |
Tracked portion of field, percent |
||
|
60 |
3.3 |
5.0 |
6.7 |
|
90 |
2.2 |
3.3 |
4.4 |
|
100 |
2.0 |
3.0 |
4.0 |
|
120 |
1.7 |
2.5 |
3.3 |
It’s important to realize however that percent of area trafficked is not necessarily equal to yield loss. There is still significant yield component flexibility in wheat plants. Due to the increased resource availability, the plants next to the wheel track will somewhat compensate for the lost plants in the trafficked area. Wheat plants next to the wheel track will most likely have increased kernel weight and potentially increased kernels/head. Additionally, some of the plants that are trafficked may still go on and contribute to grain yield.
When evaluating the economics of the decision, too often a producer may assign no cost to the operation of his own sprayer. A decision should revolve around the economics of aerial application vs. the true cost of the producer’s ground rig.
A likely range of machinery related cost (labor not included) for self-propelled sprayers is from $2.50 to $3.50/acre or $135 - $180/engine hour. This wide range results largely from the wide range in the number of acres covered per engine hour (field capacity). Variability in fuel cost is a relatively minor factor. Field capacity is affected by field size and shape, if the sprayer is tendered at the field vs. returning to an operations base, the time required to tender, and if the sprayer is transported or driven between fields.
Obviously, a true and honest evaluation of costs should include a labor charge for the operator and any labor associated with the tendering and transporting of the sprayer, especially if there are other timely task the operator could be performing (i.e. planting of row-crops).
Lucas Haag, Northwest Area Crops and Soils Specialist
lhaag@ksu.edu
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