Save the pre-harvest pass for when it's really needed


The questions about wheat harvest are starting to roll in. How do I time a pre-harvest application on my wheat crop? The answer for that question is easy: it’s all about the peduncle! (Check below for a few videos on timing a pre-harvest application correctly). Really, though, the bigger question right now for Ontario farmers is whether or not a pre-harvest pass is needed at all, especially in the hot and dry of 2020.

Generally, a pre-harvest pass serves two purposes: faster, earlier harvest, and weed control. On the weed control front, hopefully very few get caught in this “rescue” type of treatment. Good weed control should have started last fall, and, if managed, weeds are not usually a big issue in winter wheat. If you get caught for some reason, look back and sort out how to avoid that in the future.

Faster, earlier harvest is of benefit in some years, or on a crop such as soft white winter wheat where quality can go off the rails so quickly. But in a hot dry year? It is very hard to justify pre-harvest desiccation when there isn’t much of a weather threat.

What’s more, what do you gain? A dry-down with glyphosate will probably get you in the field two days sooner, and allow you to harvest at a faster ground speed of maybe an extra mile per hour. You might also have a little less harvest loss if you are really pushing harvesting into the 20 per cent moisture range with very green straw. I am a big promoter of “harvest early” and that won’t change. Once wheat is below 30% moisture, nothing good happens to it except the combine.

There’s also the chance of getting a pre-harvest pass wrong. Wheat rarely is even and uniform at harvest. Trying to time the peduncle colour change is challenging. Even if you are at 95 per cent change, there is 5 per cent that is not ready. Mostly, if you wait any longer, you barely have time to derive any benefit from the desiccation.

We should critically evaluate every pesticide application. Is it worth the small gain to use glyphosate one more time, especially with the public perception surrounding this? In most cases, the answer is a definite NO, particularly if it stays hot and dry.

Should you harvest early? YES! Drive slow, don’t lose grain, and get it in the bin with maximum quality. We have enough combine capacity for twice the corn acres and three times the soybean acres of wheat. If taking that extra day or two for harvest looks concerning, hire a neighbour to help. Harvest capacity should not be the reason for a pre-harvest pass. And weed control should be the rare failure that won’t happen again.

Hopefully, the rains return, and SOON, but if it is hot and dry, save the pass and put it towards weed control somewhere else this fall. Let’s all do our part to support the “Keep It Clean” campaign!

— Peter Johnson, RealAgriculture agronomist



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