 So cover crops and crop nutrition and the previous speaker touched on some of those things before but I want to give you Some background on it so that when you get into a situation yourself, you know How to predict a little bit what the cover crop might do for you? So there's a couple of reasons why there is nutritional benefits with cover crops number one They can trap some nitrogen in the past if we come on a crop go out soil sample and sometimes the residual soil nitrate can be significant so the idea with the cover crops is that they can grow and use that Nitrogen that the previous crop is left behind so that reduces your fall winter spring nitrogen losses And then the second thing is if the Lugumes might produce nitrogen if they have enough time previous speaker showed that using the relay cropping and I'll reproduce that slide here in a little bit They can produce some man if they have some time But if they're just in for a short period of time, maybe 30 days or so Don't look for any miracles with that but lagoons could produce nitrogen if they have the time So the release of nitrogen from the cover crops and that's where the the nitrogen comes from when you're raising a cover crop It doesn't get squirted out the roots or anything it it comes from the decomposition of the of the material and that comes We can predict Pretty pretty close anyway what the release might be from looking at the carbon and nitrogen ratio of the residue itself It it can tell you if the if the nitrogen is going to be Trapped by the by the by the decomposing crop if it's going to be released So the next crop could utilize it or neither some some CN ratios or such that really none of that happens It's just a neutral factor And that's a that's a case whether you're going to put on manure or any kind of organic amendment at all But it's it's certainly true with a cover crop. So we'll go through a couple of demos here so that you understand what I'm talking about Soil organic matter ranges from about nine parts of carbon to one part nitrogen to 11 parts nitrogen to one part carbon and average is about 10 to 1 so CN ratio about 10 to 1 is about what you'd expect in The soil organic matter and that's important because the end product of any decomposition is co2 and soil organic matter So at the end all residue good decomposition goes into that 10 to 1 organic matter pool So let's take a couple of examples here. Here's here's sawdust and It has a carbon nitrogen ratio about 200 to 1. So what what do you think might happen if you put? Sawdust on the soil. I think some of you might already know but There is nitrogen in the sawdust. So if it decomposes is it released or what happens? I'll go through this little arithmetic for you See you understand when talking about an average value for the content of any dry plant plant residues is around 45% So if we use that 45% assumption and we apply 2000 pounds of dry sawdust to the soil What we're doing is is applying 2000 pounds of sawdust times point four five or 900 pounds of carbon So we we apply that 900 pounds of carbon the ratio is 200 to 1 So if we want to find out how much nitrogen is in this in what we apply We'd divide 900 by 200 and so we have about four and a half pounds of nitrogen in the sawdust in A typical biological decomposition. This is a ballpark figure, but it's not too bad About a third of the carbon goes into the soil as a soil organic matter and The other two-thirds Goes into the year as CO2 so in our 900 pounds of carbon that we apply with a sawdust 600 pounds of that carbon goes into CO2 and The other 300 pounds goes into the soil And at the end of the decomposition that carbon from the sawdust is going to have the same ratio of nitrogen as the soil so At the end we have 300 pounds of carbon from the sawdust that's going into the soil and it has a ratio of 10 to 1 with nitrogen To make that happen there has to be 300 pounds of carbon and it needs to have three 30 pounds of nitrogen for that 10 to 1 ratio But the sawdust only had four and a half pounds Where the other 30 came from it came came from the soil So 25 and a half pounds of nitrogen was required in order to decompose that sawdust fully So a sawdust with a ratio of 200 to 1 Carbon the nitrogen can tie up nitrogen So this is an example of something that can tie up nitrogen wheat wheat residue wheat straw is another one It has a carbon nitrogen ratio of about 80 to 1 to 100 to 1 and that'll tie up nitrogen too So how about a cover crop? Let's go through a scenario here your wheat comes off nearly August field seeded the oats It comes off after after rain About a week later by the end of October when the soil temperatures to get down about zero and it kills it you figure There is about a ton of dry matter per acre and the oats were yellow green in the middle of October So there was some nitrogen there, but not a huge amount So with that you should assume maybe around two and a half percent nitrogen on a dry matter basis So let's take all those assumptions. We have 2,000 pounds of oats And it's 45% carbon. So we again have 900 pounds of carbon per acre at two and a half percent the amount of nitrogen in the oats is 2,000 times 0.025 Because the two and a half percent is measured on a dry matter basis not on a amount of carbon So so we have 50 pounds of nitrogen per acre in the oats The CN ratio of the oats cover crop then is 900 divided by the 50 900 pounds of carbon divided by the 50 pounds of of nitrogen. So it's 18 After the oats decompose we have 300 pounds of carbon and 30 pounds of nitrogen because of the 10 to 1 ratio And since we had 50 pounds per acre of nitrogen to begin with then We have 50 minus 30 or 20 pounds of nitrogen that can be released sometime in the season So generally Residues with a CN ratio of over 30 tend to tie up nitrogen and not release it Residues with a CN ratio from 20 to 30 won't affect the nitrogen status of the crop short term And the residues with a CN ratio of under 20 tend to release nitrogen and those residues like that They have fairly low CN ratios very green residues if you have If you have any kind of residue, I don't care if it's oats or rye or turnips tops or beats or You know just dream up anything anything. That's just really green Usually has a nitrogen content of around four percent So you can use that as a ballpark figure to figure out what you have And those very green residues are going to release the nitrogen the quickest so this is from European journal, you know, I I think as you go through here And I think as you go on through the morning and I apologize for not being through the whole thing my Day started out in chaos and is ending up that way The what you're finding is is most of this research is kind of in the middle That we know some things about things, but we don't know everything about things And so I guess a word of caution for you do anything is to kind of go Go to this what? Moderately with your eyes open Don't think that any of this is just real-form science and the annual climate certainly has a great Implication on how successful any of these things are going to be Anyway in this this study conducted in California They looked at the cover crop decomposition and conventional and organic fields. They were all the same The half-life of that oak veg cover crop incorporated was between 13 and 38 days So if the soils warm temperatures are good you have good moisture a lot of that really green residue can decompose really really fast Their initial effect on that was that it tied up nitrogen for a very brief period of time And then after that the CN ratio declined back down to its 10 to 1 and that's usually what happens This will work out in Massachusetts and the people on the east and the south have been raising cover crops for some time They're probably 10 10 to 15 years ahead of us as far as far as research goes and the reason they were interested in this Courser is great There is great public pressure to to clean up any kind of Nitrogen that comes off their fields. They're in a much wetter climate than we are 10 to 20 inches of rain more than we have and their their seasons are very extended In fact their winters hardly have any freezing soil in them and all And so cover crops have been a part of things for quite some time so a lot of the things that we We work with and and look at and try to figure out how it's going to relate into what we're doing in here in North Dakota Come from the east or the south so what's happening here as we have There's several different nitrogen rates in each one of those each one of those curves and As you can see they kind of plop on top of each other So the nitrogen rate that was used and head of the cover crop the residual nitrogen They had to work with isn't nearly as important as when The cover crop was was tilled under and here is this is a winter cover crop And so they've allowed it to grow all winter Which we don't have the luxury of doing a course But they let it grow all winter and then on the 1st of May they they went in and and incorporated it And then another series of treatments they incorporated that about two to three weeks later And then about two to three weeks later. So what you're seeing is a decomposition time So so we're seeing dry weight remaining in the soil from May 1st to June 1st going down about two-thirds or so and steady stating out that around around 20% for that early Incorporation and around 25 30% for the second and about a third or so for the for the third so As when they went into the season and got out of the coolness Got into the more dry conditions the decomposition rate was slower And they ended up with more dry weight more residue with the end of the decomposition period during the during the drier part of the summertime What also happens when the when things Let's see if you see this little arrow. You see the little arrow. Yes, we can Okay, here's a little arrow, and we'll just look at the first incorporation date that May 5th And this is the this is the zero end rate 60 120 180 pounds before their before their cover crop is was grown As as you go through time Here when let's Let's give it what 60 that's more likely our conditions We've a we started out with a ratio of about 29 or so as it as you go along What happens is that the more resistant materials to decomposition are left and the nitrogen is utilized And so as you go through decomposition The the CN ratio increases As you put on more nitrogen the CN ratio decreases within each one of these Treatments you see it goes from 29 to 24 and from 44 to 35 And so that's what happens the greener the things are the The higher the lower the CN ratio and the decomposition over time the residue that's left Not the stuff that's in the soil organic matter But the residue that you're seeing is really really high CN stuff and it takes more nitrogen from the soil to To get that to rot This is what happens in our environment. This is the mineralization right through the season. This is how fast things rot We look at it And there shouldn't be a tail here This is just an artifact of the program. But anyway if we go in the March, it's really cold There's ice in the ground nothing's happening as the soil warms up We have have this burst of activity out into May and early June and this is the peak This is the peak of our of our residue mineralization, right? And then as we go back into the fall then the things go down quite a bit And so as we go out into September October or so When a lot of your fall cover crops are gonna go a lot of that mineralization doesn't happen in the fall And that's a good thing because if it did then we might lose that nitrogen over the winter time So so it goes down to this very almost zero level and then the real Decomposition of those residues happens then in April and May and that's a good thing for all of our crops because There's those are the periods when the crop is going to need it most so If we do get some nitrogen stored in the fall of the year Then we can expect it to be released fairly early in the spring time because that's our crop growth spring We eat we're putting it in in April sometime. Hopefully And and so the nitrogen and the peak of the nitrogen mineralization just precedes or just Just hits that area really really Rapid growth and nitrogen uptake so it's it's not a bad it's not a bad mix All right, so how do you do this? There's a couple ways to do it I'll show you two ways this boat this first way is the most scientific way So if you have a if you have a little scale You can pick these up at a hardware store for I don't know 20 30 bucks or so What you do is you go out with a square You put some PVC pipe together or so and throw a few of them around and you collect the the above ground plant material from that foot-by-foot material you dry it and then you weigh it and So if you have two thousand pounds of dry matter and acre that's going to weigh 20.8 grams on a foot-by-foot basis so in another way, you know for every one gram That you find per square foot. That's Roughly a hundred pounds, you know exactly pretty close to exactly 96 So if you want one gram is a hundred pounds. That's a pretty good rule of thumb So that's one way that you can measure how much you have And then if you figure that your that your cover crop tops are very green Then you should assume that it has about four percent organic matter And then you can kind of figure out about how much nitrogen is left from the carbon nitrogen ratio at the end Every hundred pounds of dry matter is going to contain four pounds of end per acre for the next crop then figure about a third Available if it's conventional tiller if you're a no-till you can't figure that much because the decomposition is slower So about 20% if it's no till on one pass seeded So those are the numbers you need in order to figure out what you have if you want to do it scientifically but If you don't have that much time and math is not your friend Then you could do it this way if you have if you have a cover crop out there And you've seen pictures of cover crops that completely cover the field once you have the the field completely covered With the cover crops with an annual legume a pea Let's say you you grew peas you dist them down and then you have them come back up again, and you have a six inch height That's two thousand pounds of dry matter and every additional inch in height is about a hundred and fifty pounds of dry matter So you could do this with just a yardstick If you have rye or any kind of a annual small grain Eight inches high completely covering the the field a really dense stand. That's around two thousand pounds of dry matter Let's give you an example of What we see sometimes this is the field that I work with and in a corn study this year done by Rutland and the grower Had fall cover cropped and then grazed and then the strip tilled in the fall and implanted in the spring And in between the rows you can see the residue this left In the fall of the year it looks monstrous, but once cows come through It's doesn't look a whole lot different than just having beans double out there a lot less dense than if you have weeds double A lot of not a cycling going on in this field though the the growers been in no till for over 20 years So he has a lot of help for bugs in the soil that helped to turn that stuff under Another reason I put this in here is because this is this is my only what attempted at cover crop research won't call it that But I had 20 sites this year and my corn study in the east couple of them were out at Carrington The Greg Endress took care of But most of the rest of them were in the east and this one in Rutland was the only one in Sargent County And it was the most efficient use of in I gave If you figure out the total available land that that was That I could figure out He would give a 50 pound credit for long-term no till that's something we found in our wheat research a couple of years ago And it seems to so far be valid in the corn research I've done he has a 50 pound credit because the organic matter is over 6% So that's another 50 pound credit his residual nitrate before the Before the study happened in the spring was 68 pounds But then I subtracted off 30 pounds of that Because he had a really good wheat crop the year before and so I subtracted 30 pounds off for excessive straw So He raised about 190 bushel corn an acre with Around 138 pounds per acre of known available land plus the 40 pound end rate So it's a little bit less than a pound of end for bushel, which was my most efficient site So I'm gonna be working with them in the next couple years on some some sites It also had cover crop and and see if they continue to be different from the other sites that I manage right now I don't know if this is real or not or if it's just a An artifact because it's it's not replicated it's just a site that's different than the other 19 I want to I want to put this in here To see how well your glasses work. No, I put want to put this in here to Show what happens when you put multiple crops in When you put multiple crops in it's it's kind of like putting a crop and a weed together There's a lot to talk about cocktail mixes and all that's great But there are certain there are certain plants that are going to just kind of take over So this is this is some work with some oats seeded with a clover crop And what we're seeing over here is If we're looking at the total biomass over here of the two of them together Let's say up here at the at the August 5th They're looking over what two and a half ton or something like that a total biomass, but But over two and a half ton of that is Is the oats only a very small amount of that is the is the clover the clover really doesn't take off Until the oats give up and that's what you'll see a lot of times if you put lots of things together That the more aggressive plants the ones that like that whatever conditions are there when when you're seeding them Those are going to take off and tend to dominate if you continue to grow after after a while until that aggressive thing is either cut or Or dies away then the other crop is going to take over but If if you're seeding thickly enough to be a very good cover crop I would try to tend to avoid things that are going to smother the other things out Especially if you're going to put it in the fall of the year and it's only going to grow So you put it in the middle of August and you've got September and October that you can really count on before the weather turns horrible so In that 60 days you just want to make sure that you have that that you spend your seed dollar wisely and put things in that They're actually going to have a chance of being of assistance to you not not like this if we gave this 30 days or so From the from this planning date you'd have decent growth with the oats, but But hardly hardly anything with the with the clover so so think about what you're doing before you do it make sure that All the crops are going to do well The thing to thing to remember is the cover crop legumes are only going to make nitrogen if two things happen one They have a long enough time to work Which means more than 30 days and the second is if there is plenty of residual nitrogen afterward They're not going to make it make any nitrogen at all. They'll still be green. They'll still be healthy They may even nodulate but as far as nitrogen production themselves They're not going to make any nitrogen until the nitrogen in the soil is depleted So the last couple years has been a no-brainer you go after after small grains and the nitrogen in the soil is Extremely depleted and so that really hasn't been a problem, but let's go back maybe three years ago West River when they had the drought and they had a hundred hundred hundred twenty pounds of nitrogen In the soil and then maybe you got some rain afterward And then you try to put in some legume to to get some more nitrogen that legume won't won't make a pound of nitrogen Because all it's doing is just sucking up the nitrogen in the soil so Think about think about the benefits of legumes especially if they're going to be If the seed is going to be much more expensive than something else that you could grow If you do grow a cover crop and you're not of course not putting any nitrogen on there Your job is not to feed the cover crop your job is to feed the crop that's going to pay you But if you put a proper crop and and you find that it's kind of yellow green or even yellow The chances of that really supplying a nitrogen for the next year are very very small because again the CN ratio will be so large That it it probably would just be a neutral factor to the coming coming year There's some work with this a number years ago back in 95. There was a year when There was a lot of volunteer grains after wheat harvest and so a member of our department went out and and took took Took residue from areas where the Where the volunteer wheat was green and yellow green and yellow and he found a good nitrogen contribution with the really green wheat a So-so Contribution with the yellow green wheat and if the wheat was really yellow. It didn't have any nitrogen benefit the following year So that's another thing to keep in mind is you're looking at your fields and figuring out Trying to figure out what the benefit might be the next year so that you might be able to take a credit so A lot of the green things Harry vetch for example where it has a nitrogen replacement value of about 50 to 70 pounds an acre There's probably a lot more nitrogen in in the vetch than that But this is this is what's available remember that some of that carbon is going back in the organic matter So not all the nitrogen that's that's being produced by these crops are held by these crops are going to the next crop so Again if you figure out that you have say, you know 80 pounds of nitrogen in In a in a cover crop Don't give a 80 pound credit because only a portion of that is going to be used by the next crop and then In their study with the rye If they killed it directly had a seeding it actually had an initial negative nitrogen replacement value 20 30 pounds of n per acre And they got by this by killing it a couple weeks beforehand Whether whether you want to do that a lot of times we get such a hurry in the spring time because we have to All the water we've had lately that we don't have the luxury of waiting a few weeks in order to plant so What what certain cover crops depends on on how much nitrogen they have in them They could have a negative nitrogen replacement value if they don't have enough nitrogen One of the things I worried about when people started putting oil seed ranish in the ground was that that family of crops does not Support my cariza which is a fundus fungus in the soil that supplies a lot of our plant families with Phosphate and some micronutrients zinc for example And a lot of our crops corn wheat soybeans sunflower Are very dependent on the my cariza in the soil flax particularly so But the mustard family crops and lamb's quarter family crops don't support them So I was worried that if if we put out oil seed ranish that maybe in the next year We went into a crop we might get into some phosphate deficiencies because the micro riso was decreased Well, there was a study what last year published that The micro riso wasn't in inhibited by the cover crop. I guess, you know, it's not around long enough in order to To make the my cariza population go down enough that it hurts the next crop rye actually enhances the the my cariza and I think a lot of other Other plants would too, but the oil oil seed ranish all of those family crops you'd expect sugar beets to be the same way Those don't seem to inhibit The the my cariza if grown just for a very short period of time if you grew them all season they certainly would just like canola contributes to a fallow syndrome after canola and Sugar beets contributes to fallow syndrome on corn So how about studies that looked at the yields the next year and and these have been what? All over the board some have seen some Some seen some advantages and some have not There's a recent study in Iowa We started looking at At cover crops and they used an inner seeding of of cure clover Which is an adapted clover for that area? And it didn't influence the soil nitrate before during or after the season seemed to be a neutral factor Sometimes the excessive clover growth reduced the corn yield and I think this had a lot to do with the water Situation during the year The suppression of the clover during the corn growth resulted in similar corn yields In in both the cure and the non-cura system So it I guess the bottom line the Iowa study is it really didn't wasn't very helpful to them Cons condel which some of you some of you know, you know, I don't know if he's on the program today or not But you know, he's not maybe you should be given us, but he's done a lot of work at NDSU during his Days as a PhD candidate He worked with intercropping sunflowers legumes, and I've seen this done in the organic community They've done this for a very long time They used at five site years and prospering Carrington black lentil hairy vetch Oh, yellow blossom sweet clover snail medic seeded at the time of sunflower seeding it reduced the yields Except with black lentil it didn't seem to and the yield of sunflowers wasn't suppressed when it was seeded a v4 v10 So that was good and then the biomass of legumes at later seeding day range from about 1,500 pounds for the v4 seeding to about 800 pounds an acre for the v10 so He one of his conclusions was that the sweet clover seeded v4 could act as a cover crop for the next growing season two since it's a biennial So there were significant legumes produced with this method In a companion study, he also looked at what happened to the wheat crop afterward And what he found was that the spring wheat seeded the year after the sunflower Wasn't really enhanced by the intercrop legumes Couldn't really explain why that was but the data supported that that was the case What he didn't show was could he save any nitrogen and I don't know if he Brought that out or not. I don't think he did So most of our cover crops, you know, it's thinking about cover crops after we combine corn or combine soybeans I think is his most year is going to be a Non-issue because they're late enough in the season harvesting. There's really no time So most of our cover crops are going to be seeded after short season crops such as barley, canola, or spring wheat And then you've seen the data from this before how the relay cover crop just growing an annual legume And then let it grow again Also, the Organic growers do this sometimes with buckwheat to let the buckwheat grow and then they'll disc it in and the buckwheat comes up again And then I'll turn that down as a cover crop and it actually helps their phosphate nutrition So we do that with the with the field peas and that works pretty well for the most part the We look at the numbers here 63 69 you can generally assume that after pea crop you're gonna have a maybe 20 pounds of in In the top couple feet. So probably about 40 to 40 40 to 50 pounds of this end Is due to the nodulation. They had enough time between the harvest and That mid-october date When they read the biomass that they're getting about 40 50 pounds of in and here in a really really thick stands were as the As the presenter said they didn't have a combine said as well as they should they could have There they really had a lot of nitrogen produced in that in that situation And then one more thing I wanted to mention we haven't talked about moisture at all but I think in these times of Excessive water and that just having an extra crop out there to use more water is a good thing and 15 years ago somebody would never have talked about this Because at that time you wanted to save every drop of water that you wanted to but there are many times during the past 15 years 12 years or so, you know since what 92 or so this has gone on for a long time, hasn't it? That we've had excessive water So sometimes for certain crops having something else out there that's using water is a good thing This is a Minnesota study and I I worked with this study too. They got much better results than I did. This is this is cool soybean. It is chlorotic and this is No nitrogen With the cover crop over here. This is oat seeded the same time that the soybeans were applied were put in They just the field with the oats and then planted the soybeans on top of them So here without the cover crop we have lots and lots of chlorosis and here we have a little bit But they're much more robust and green. These are both pictures shot the same day And then with a hundred pounds van with residual in out there With no cover crop the soybeans are really really suffering here the excess nitrogen nitrate in the soil actually increases amount of The monoclerosis that you have and here with a cover crop Again much much greener much taller much healthier. So so by taking Some nitrogen from the soil They're helping this but also the biggest benefit as you can see up here where there wasn't any nitrogen applied at all It's just the moisture conservation as the soil becomes drier There's more not there's more iron available for the plant When the when the soil becomes saturated That's when bicarbonate is produced and and the chlorosis becomes really bad so If a person has a real chlorotic field an old cover crop and then kill with roundup or another another herbicide is Not a bad not a bad cultural tool to try to get rid of some of that chlorosis because it can injure the plants a lot So summarize this a cover crops have the ability to tie up available and and protect it from loss The timing of the cover crop release isn't you know of nitrogen is critical to its success But I don't think we have a problem with that given the amount of mineralization that happens in the fall And it's and then the early spring it seems to nick pretty well The carbon nitrogen ratio of the cover crop helps to determine how much nitrogen is becoming available And the legumes in the mix may or may not have time to nodulate and produce and in many years So they need about 30 days if you don't have that then It's it's not going to be worthwhile to pay extra money for and then also This whole cover crop thing is is driven by a number of a number of factors But when you go out and look at field tours and different things I want you to keep something in mind that when you're evaluating it Remember the data without replication is not data. It can't be evaluated Critically it's it's really no more use than copies coffee shop talk If you if you look at what the grower has done and he does it in replicated strips And has a yield monitor or some other way to measure Measure the progress and in related statistically Has an oversight partner as a collaborator. That's that's real data And that's what takes so long on our end and to Give really firm recommendations about something so complex as this is that It takes time and energy and patience to Get data that's that's really really useful so with that I think I can take some Questions if you have some Are there any questions for Dave? We got one over here Dave. What's the question? I might have to repeat it The question was has there been any data or experience in using cover crops to break down land that's coming out of CRP I mean break down the residues. I Assume so yeah And speed like it's like all that type of stuff. No, I don't I don't know of any I I think something like that would would still be long term. It takes a while for To get enough cycling and enough diversity of your microbiology Population in order to make that work Dave. They've got an ongoing one down at Pingry wrong leader holds and The Stutzman County STD had one looking at that. I don't have any of the data But I know they did start that They did the cover crop not dead this year was their test crop here So the cover crop went in last year Their cover crop would have went in the fall of 09 Summer fall of 09 But I haven't seen any of the data, but that's what that's the only thing that I know of okay. We'll have to get a hold of that