Cover Crops

(Kraig) We’ve been looking at cover crops in a wheat, sorghum, soybean rotation where we insert cover crops between the wheat and the sorghum. We’ve also looked at cover crops between soybeans and corn. If we’re really after residue, we want things like the cereals, the summer annuals like sorghum sedan, millets, things like that. They produce residue that typically doesn’t break down as quickly, provides additional benefits in terms of water infiltration, preventing water evaporative losses, that kind of thing. If you’re looking at nitrogen contribution or scavenging nitrogen especially, you may want to look at brassicas, things like the rapeseed or the radishes, very deep tap roots, go down and get nitrogen that may be left after your grain crop, bring it up to the surface and incorporate it into residues that will turn over very quickly. Now, it’s not like you get a big shot of nitrogen. But they increase the background level of nitrogen and our research has shown that you can apply anywhere from 40 to 50 pounds less nitrogen to the next sorghum crop say, and get similar yields to what you would get in if you hadn’t had the cover crop there. If you’re producing biomass, any kind of top growth, grazing that crop, they’re going to be using water. And that’s one of the issues in our Kansas cropping systems is the water use. Are we going to hurt subsequent crops by having that cover crop in place? In environments where we’re 20-25 inches or more of annual precipitation, if you’re careful and you have reasonable rainfall amount and distribution, we see minimal negative impacts of these cover crops on the next grain crop. As you move west and drop below 20-25 inches of annual precip per year, yes there’s a very large potential to have water extraction that’s going to have a negative impact on that next wheat crop primarily. And so you need to factor that in and look at ways to manage that cover crop in a way to minimize the effect or get more value out of that cover crop to pay for that negative impact on that next crop. Forage use is one way to do that.

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