Cereal Rye Before Corn: Allelopathy Myths and Nitrogen Management

0:00 Hey everybody, Keith Burns with Green Cover here. Everybody knows that cereal rye is the undisputed champion of cover crops. It's more widely planted than any other cover crop by far and with good reason. It is the most aggressive. It can be planted the latest. It's the most cold tolerant, the most deep rooted. It's a superstar of the cover crop world. And it's a fantastic crop ahead of soybeans because it ties up all that.

0:29 Nitrogen. It does great weed suppression. It's just a really natural fit ahead of soybeans. But a lot of people are afraid to use cereal rye ahead of corn. And there are some reasons for that. Now, one reason that people say, well, it has an allopathic effect on the corn. And I want to just talk about whether or not that's true or not. Now it is true that cereal rye definitely has allopathic properties.

0:55 Allelopathic means it chemically inhibits the germination of seeds and it's true that it does that when we look at cereal rye residue you see very few of the small seeded weeds come through. It will almost completely eliminate marsh tail as a problem in the spring because it's allelopathic to those small seeded weeds and that's one of the reasons we love cereal rye as a cover crop because of that allelopathic effect. Now does it

1:26 Have that same effect on our crops because we would not want that to happen with our corn or soybeans and the answer is no. We just don't see that happen. You don't see a reduced germination in your corn crop or your soybean crop. The allelopathy generally happens only with the small seeded things like mostly your weeds. Now, you would not want to plant canola or something like that into heavy cereal.

1:52 Rye residue because it could be allelopathic to those. It could stunt those. So is cereal rye allelopathic to corn? We really don't see that. There could be certain situations where a decomposing rye can have some effect on corn seed germination, but it's extremely, extremely rare. In fact, so rare that we really don't even worry about that. Now, that does not mean there aren't management issues or concerns with

2:20 Planting corn into a heavy cereal rye cover crop. And that's why I'm kneeling here in this corn field of ours here at Providence Farms Green Cover right here in Blade, Nebraska. Because this corn was planted into cereal rye that we let get 5 feet tall. We rolled it down. We sprayed it out just to make sure the rye didn't come back. And then we planted corn immediately into that big thick thatch of cereal rye.

2:49 Think this corn looks pretty good. It is not suffering. So certainly no allelopathy. All the seeds came up, no allelopathy. But what can happen with corn planted into cereal rye is nitrogen tie up. And it is not uncommon to see people talk about a yield drag with corn into cereal rye. That is not allelopathy. That is a nutrient cycling issue. Because this cereal rye when it got 5 ft tall, one of the greatest things it does is it

3:46 Stunted corn. I will have a yield hit if I don't manage my nitrogen properly because there's no nitrogen left in the soil available for that newly emerging corn plant if you let your rye get pretty big. Now, that doesn't mean you can't do it or you shouldn't do it. It just means you have to understand what is happening and manage around it. And so what we did here, we applied no nitrogen ahead of planting this corn.

4:15 Because if I would have, it would all have been tied up in this cereal rye. So we put our nitrogen onto this corn crop after we planted. We streamed on about 75 lbs of nitrogen right after we planted this. Now, we do have the fortune of having a pivot here. And then through the pivot, we were able to apply nitrogen at several other stages throughout the life cycle of this corn. So all told, this has probably had

4:41 Around 140 to 150 units of nitrogen. And we're expecting this corn to make 230 to 250 bushels. So it's a pretty good nitrogen use efficiency. It's very clean. You look down this row, there's hardly any weeds growing at all. And the only chemical application this has had the entire year was a little bit of liberty to kill this cereal rye after we had rolled it down just to make sure it died.

5:13 And we may not have even had to do that. So cereal rye is extremely effective at preventing weeds, extremely good at sequestering the nitrogen in your soil. All good things. You just have to understand how to manage your nitrogen if you want to plant corn into a heavy cereal rye.

5:32 Is yellow corn after rye allelopathic? No, it is not. But it is a problem. So make sure you understand how to manage your nitrogen. If you plant corn into a cereal rye cover crop, contact any of us here at Green Co. We can help step you through the management that it takes to do this because rye is the king of cover crops.

5:55 It is the champion because it does all of these good things. Don't take it out of your corn rotation because you think it's allelopathic. You can manage around it.