Do Cover Crops Use Up Your Moisture? What the Data Shows

0:05 Get asked two questions: number one, how did you get started with green cover, and number two, won't cover crops use up all of my moisture?

0:15 I want to briefly address both of these questions because they're actually very closely interrelated and by answering one it will help answer the other.

0:24 So green cover actually started, or at least the idea of green cover started with the 2006 No-Till on the Plains winter conference in Salina, Kansas. A man named Adamir Calligari from Brazil came and talked to us about cover crops, but specifically multi-species cover crops. It was a very exciting talk and it was showing some great things that the farmers in Brazil were doing with this concept.

0:49 Now Jay Fuhrer and Gabe Brown took this concept home to Bismarck, North Dakota and they started experimenting with cover crops, multi-species cover crops.

0:59 2006. And my brother Brian and I started talking about we should do something like this as well so in 2008 a couple years later we wrote a small Sarah grant. We got about five thousand dollars in funding and we bought moisture sensing equipment because our question was but won't these cover crops use all of the moisture that we could save in our wheat stubble for the next year's crop and we didn't feel like we could proceed into cover crops until we answered that question.

1:27 So we got this Sarah grant, we got these Watermark sensors and data loggers and we had 18 different plots that we planted after wheat harvest and we had moisture sensors at one foot, two foot, and three foot depths and we took daily readings on these between August 15th and November 15th and this is in 2008 and we had pretty good moisture that year in the late summer and the fall so we had the different cover crops planted in these strips and then we also planted the rest of an 80 acre.

1:58 field with a mixture of seed for the livestock to graze. So we had, I think, 15 different strips of monoculture cover crops, three strips of cover crop mixes, and then one strip where we monitored moisture in wheat stubble by itself. And the biggest thing that we found is that cover crop mixes are much more efficient at water usage than the monocultures were.

2:21 Let me show you what I mean. Here's the results of what we found. Now, the way you read these graphs is that the higher the bars are or the higher the lines are, the less moisture it was using. The lower down on the chart, the more moisture that whatever was growing had pulled from the soil.

2:39 This is a chart of wheat stubble. So wheat stubble, no weeds growing, nothing there, just plain wheat stubble. This was stripper stubble, so it was fairly tall, pretty decent stubble. And you can see, not surprisingly, that there wasn't a lot of moisture usage in the wheat stubble, but there actually was a

2:56 Little bit later in the season now, soybeans that was one of the cover crop scripts that we planted. You can see a lot of ups and downs, which means there was a lot of moisture use. Seeds there were some recharge from rainfall events, but throughout the course of the year the graph keeps going down, down, down, which means there was moisture being pulled from the profile.

3:17 Same thing with common batch. It's even a heavier water user later in the season, and it pulled it down quite a bit by the end of the fall with common veg by itself.

3:30 But here's what was really stunning to us. We had two mixtures — this is mix number one and this is mix number two — and both of these mixes showed very efficient water use. We don't really know even how to explain this, and if it was just one mix we would have thought maybe there was something wrong with their data loggers, but this was fairly consistent with both mixes and basically what it's showing is that.

3:55 There was something going on in that mixture of seeds that it made the system use the moisture much more efficiently, and by the end of the season the recharge had completely replaced everything that the cover crops had used. And again we were a little bit hesitant to even share this type of information until we started hearing and seeing what Gabe and Jay had done up in Bismarck, North Dakota.

4:20 You've probably seen these pictures before because they're very famous. They've been spread around a lot because they're pretty stunning in what they show. And really what they're showing is the visual representation of the same thing that our graphs and our Watermark sensors were showing with moisture usage.

4:34 So this is the experiment that they ran in 2006 in the summer of 2006 after they heard Adamir speak at the Notes on the Plains event. And so they went back to Bismarck, North Dakota and they planted strips of cover crops and monoculture, and then they also.

4:49 Planted some mixes and this is the result. Now they had an extremely dry year, they had less than one inch of rain from when they planted this. They planted this May 30th, these pictures were taken the end of July, so about 60 days later, 60 days of growth with three inches of rain for the whole year and an inch of rain since planting.

5:08 Just what you would expect, the turnips had pretty well burned up. They grew a little bit, they burned up. Radishes the same way, they grew a little bit and they just burned up in these monoculture strips. All their monoculture strips showed this, but where they planted the mix, this is what they had.

5:24 And I know you can, if you can see very well, but clear over in the upper right hand corner you can kind of see a little brown strip. That's where those monoculture strips are. So it's all in the same field, this is all dry land, and the mix for, you know, reasons that are not widely understood, but we have.

5:42 Some theorization about it, simply use the moisture that it had much more efficiently and produced a very impressive amount of biomass on an inch of rain. Now how can it do that? Well, there's a lot of biological processes going on. These pictures are a visual representation of what we saw on our charts and our graphs with the watermark moisture sensors. In a very dry year, they demonstrated that cover crop mixes use water much more efficiently and can produce a lot of biomass on very little moisture.

6:16 For us in a relatively moist year, we saw that the moisture replaced with the cover crop used, so either way the cover crop mixes are much more efficient. A couple of other studies that back this up as well. This is also up in North Dakota. This was in 2007. Marlon Richter, who is also in that Burley County group, they did this experiment. They harvested peas double in July, and on the left-hand side of this tree.

7:43 So essentially, this was measured the next spring in April. What happened is the cover crop used moisture in the fall to grow, but it was all replaced by snow catch. It was replaced by reducing evaporation, it was replaced by better infiltration. And in the end, come the next April, there was almost no difference in the amount of water available for the next crop. Because the cover crop not only was efficient with how much water it used in the diverse mix, but it also recovered it through better infiltration and less evaporation.

8:20 One last study here just to show you. Dwayne back at Dakota lakes research farm, this is in 2010 and 11. They did a similar type experiment where they planted all these cover crops in the summer and then they measured the amount of available water both in November at the end of the growing season in South Dakota and then also at the end of April.

8:41 Would be when they would plant their next crop and so what you see here is that the cover crop mixes are at the bottom here and there was 3.76 inches difference in water availability in the fall. The mixes, the cover crop mixes said use more water at that point in time whereas the checks with no nothing growing were up here at the six inch level but by the time they get around to the end of April there was significantly less difference of 0.84 from top to bottom and most of the mixes are actually up here almost exactly with where the fallow ground was and so again what they're showing is that the recovery, that the cover crops particularly the diverse mixes allow through better snow catch through better infiltration and less evaporation made up for almost all of the moisture usage from the cover crops.

9:35 So to maximize the moisture we think that context is the key you have to understand the context of where you're.

9:42 Growing this, you can't if you're in an arid environment you can't do the same thing that farmers in Iowa and Indiana do. Here in Nebraska we can't do the same thing on our dry land that we do on our irrigated because they have different contexts. So just a few rules of thumb that we like to employ, particularly in arid areas, we want to plant a diverse mix every time we can because of the data that I just showed you. We're big believers that diversity means more resiliency and it means more water efficiency. Number two, we want to plant appropriate seeding rates. We know we have to plant lower seeding rates where we have lower rainfall. So again, plant the seeding rates that are appropriate. Our smart mix calculator takes that into account based on your rainfall and our salesman can help you figure out what those rates are if you need help doing that. Yeah, this is an important one right here. If you're in an arid area, we really encourage summer.

10:40 Planting of cover crops and then let the frost or let the winter terminate them and don't have anything that overwinters and they're growing out there if you're in a really arid environment because that's the time when you need to be recovering the moisture and storing the moisture up for that next crop and if you do have some overwintering species which is okay as long as you're ready and willing to manage it. If it looks dry you got to terminate early and if it looks wet you can let it grow out. So again it's all about the context, it's all about managing the cover crops to the context of your situation.

11:14 So do cover crops use moisture? Yes, anything that grows is going to use moisture but with proper management and with a proper understanding of your context you can make it work and you can grow lots of forage for your animals. You can do a lot of improvement for your soil and you can turn your moisture into a lot of benefits and then recover it on the back side with better infiltration, less evaporation, and healthier soil.