Variable rate fungicide effective in some cases

Many growers have asked me lately about variable rate fungicide applications.

They want to know how much it will save them compared to single rates of application. It has been an interesting topic because growers are trying to make the most from their input dollars.

One of the key things that growers need to know before buying this service is that they must follow the label from the chemical company in regards to application rates.

I don’t know how many times I have heard, “we will just use half rate and we will save money.” It might be true, but it is an unregistered application rate. The label is our bible for what rates we must use.

There is a code of ethics that I have to adhere to as a certified crop adviser. It is no different than my professional agrologist colleagues, who also have a code of ethics.

For this reason we cannot recommend off label rates, or what is called “half rates.”

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This leads to the question, “what is my return on investment (ROI) if I can’t legally use half rates?”

To answer this question when looking at variable rate fungicide (VRFg), let’s focus on canola because traditionally it has been the crop with the largest expense for fungicide and the hardest one for the grower to make an application decision.

We know every field is different, which is particularly true with VRFg. Using a cost factor of $3.75 per acre for the service, the worst case, after cost, is a $2.94 per acre loss, while the best case, after cost, is a return of $1.35 per acre.

We have seen positive returns of more than $10 per acre, after cost, using multiple new technologies, but we are finalizing the data.

Field variability is key when making decisions. On our best case scenario, 24.2 percent of the acres didn’t require a fungicide application, and only 15.8 percent required a high rate.

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When we brought the existing VRFg application model to our customers, they felt that the returns were not adequate for the risk that was required. However, we have had significant interest from some of our clients in the use of multiple technologies to reduce sclerotinia losses and increase the ROI from using this means of technology.

So did we answer the question about what ROI to expect when using VRFg?

I know there may be situations where a higher percentage of acres don’t need an application, but if your fields have areas where moisture levels are high in lower areas, then variable rates would provide the returns for which you are looking.

From our experience, I do not feel that we can promise a positive ROI by using the existing model on every field on every farm.

Producers need to know what they are getting from their service provider and shouldn’t be afraid to ask for data to support ROI claims on a field by field basis, because that is what this technology requires.

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Garth Donald, CCA, heads agronomy at Decisive Farming in Irricana, Alta. You can reach him with column ideas and questions at 800-941-4811.