Fall manure: Should you use a nitrification inhibitor?

University of Minnesota Extension manure management specialist Melissa Wilson talks with the Linder Farm Network about recommendations for fall manure applications.

TRANSCRIPT

Linder Farm Network: It’s time for the AFREC Spotlight, the Agricultural Fertilizer Research and Education Council. Doctor Melissa Wilson, University of Minnesota Manure Management Specialist, has recommendations for fall timing of manure applications.

Melissa Wilson: It’s good to think about timing as one of the best management practices for manure application. And typically, we find that manures, when they’re applied later in the fall because the soil temperatures are cooler, they’re less likely to see yield hit than if we apply manure earlier in the fall. And we think that’s because with nitrogen in the manure being so fickle, just like it is with fertilizer, it can, the earlier it’s applied in the fall when soil temperatures are still warm, the microbes are still feeding and taking up that nitrogen and potentially converting it to nitrates, which then can be lost if we get a wet fall or a wet spring. So, if we wait until soil temperatures are cooler, we usually see better yield outcomes the next year. But that can change, like if you have other things going on and you want to stack some other best management practices on top of that or use them in place of that. Soil temperatures are cooling, but we’re still a few weeks away, for instance, from the soil temperatures reaching 50 degrees.

Nitrifications inhibitor for our liquid manures can be helpful. We’ve seen some evidence, particularly in swine manure, that it works really well. In dairy manure, we’ve seen that it can, it still works, but it doesn’t seem to translate to yield as much. So, we do see that it will help the soil, the soil ammonium or the ammonium in the manure really to stay in the ammonium form rather than the nitrate form.

But those inhibitors only last so long. So, if you’re applying manure even earlier than that, say late September, soil temperatures aren’t really quite starting to cool yet, then definitely getting a cover crop on the field as soon as possible and growing whether it’s before or after the manure is applied can be beneficial, especially if there’s a lot of growth in the fall. The roots can take up those nutrients and hold them in place and then be releasing them the next year.

Linder Farm Network: For more information, visit mnsoilfertility.com.