Good day everyone and welcome back to our class. As you can see, we're already in Week 6 of our course. Today's lecture, I want to continue to cover some of the material that dealing with fertilizer management, specifically continuing with our discussion of the four Rs. Recall, we've talked a little bit about the right rate of fertilizer and we, we discussed quite a bit about soil testing and calculating amounts of fertilizer, and we got a little bit into some math and, and, I'm sure everyone enjoyed that part, and we'll continue that. I want to give you some problem sets to continue to practice with the mathematical side of, of these issues. I want to point out that as we go forward, we're not only talking about rate. Rate is a very important part of a fertilizer BMP, but sometimes, we get too concerned about rate, as if it were the only part of a fertilizer management BM, BMP. Sometimes, neglecting the idea that there are other aspects that might affect how efficient we are with the amount of fertilizer that we choose. And one of those aspects is placement. We typically have a couple choices when we talk about fertilizer placement on the farm broadcasting or banding. In broadcasting, we're really discussing or talking about spreading a fertilizer material uniformly over the surface of the field. In some cases, this fertilizer material may eventually get incorporated by tillage or we might plan that a pending rain or an irrigation event will help move that fertilizer material into the soil and hopefully into the root zone. Broadcasting is usually easier and quicker than the alternative banding. But most research shows that broadcasting is less efficient in terms of the proportion of the fertilizer that's actually used by the crop, particularly early in the season when the crops have not developed a full root zone to intercept the broadcast fertilizer. Also, recall our discussion about nitrogen transformations in fates and flows. And in this case the kind of fertilizer, or the type of fertilizer, that we may choose for broadcasting may be affected by some of those conversions particularly, for example, urea. If we spread urea on the surface of the soil and leave it there we could lose some of that urea to volatilization. So, we, we need to be careful about the form of fertilizer that we choose if we are going to practice broadcasting. So, the sources of N would be important in that regard. Here are a few examples of broadcasting, manual broadcasting, in the upper left-hand corner. In the upper right-hand corner, we're spreading a dry fertilizer material by broadcasting it uniformly over the field. In the lower picture, you'll see a truck applying a liquid fertilizer in broadcast fashion over the field. Banding is an alternate choice and there are times when we might prefer to use banding and I've given you a few examples of those. Banding usually ends up placing the fertilizer nearer to the, the root zone in a band, as its name implies, a continuous stream of fertilizer in the ground alongside of the, the row of plants. It usually involves subsurface placement but it doesn't always have to. But typically, we're talking about using some kind of mechanical device and I'll show you some of these to place the fertilizer under the soil surface in the root zone. It's very useful early in the season when the plants have not developed a full and expansive root zone it reduces the mixing of the fertilizer with the soil, as with broadcast might result in. And this helps if we're applying phosphorous or potassium on the soil that would fix that those nutrients fairly quickly so that they would not be available to the plant roots if the plant roots were able to intercept them. Often with banding, because the efficiency is typically a little bit higher than broadcasting, the overall fertilizer efficiency is increased. And banding would be considered a best management practice in many, many growing situations, for example, with potatoes early in the season when the root, root mass is not developed sufficiently. And I'll show you some pictures of how the system. Here's an illustration of banding early in the season. Typically we, we use the term 2 by 2, which means that the band of fertilizers placed 2 or, or may be 3 inches to the side and below the surface of the soil. And I've given you a couple different scenarios here how bands might be a placed, might be placed in the soil with different planting patterns. Now, banding does have some challenges associated with it and that is you, while you are placing the fertilizer in a band near the root zone, you don't want to get it too close to the plant. Soluble salt injury may be the result and I've given you a couple examples of soluble salt injury, one with plastic mulch, in the top picture, where you can see that the plants have been damaged and also in the lower right-hand corner, which are young corn seedlings that were exposed to a band of fertilizer too close to, to the roots. Here's an example of potato crops with potato in the upper picture showing that the canopy is not covered and so, a, a piece of equipment may still be able to go through this field and apply a fertilizer band. While in the picture in the bottom, the canopy has closed and it's impossible to get a applicator through the field. In this particular case, with this particular farm I'm familiar with later in the season the farmer applies fertilizer through the center pivot irrigation system, in a broadcast fashion in that case, and we'll take a look at that in a bit. Starter fertilizers are usually mixers of nitrogen and phosphorous and they are put in very small amounts near or with the seeds or transplants not enough to cause injury to the seed or to the transplants, but they're very important particularly on cool and wet soils early in the planting season in Northern climates because the fertilizer is right there at the germinating seed and it helps get these plants, for example, in this picture, it shows, you it shows corn plants responding to the application of starter fertilizers. So, you see where the starter fertilizer was used, the corn plants got off to a much faster start and are further along than the corn plants in the, in the near part of the picture where they did not receive starter. The starter fertilizers we'll come back to are particularly important. This banding application of fertilizers is particularly important in some no-till production systems, and we'll talk a little more about that in a second. So, some of the factors that one might consider when choosing between whether to broadcast fertilizer or band fertilizer, I've listed here. We've touched on the idea of the stage of growth. Banding fertilizers early in the production season would be a more efficient placement and utilization of nutrients. And then, maybe a broadcast application later on when the roots have filled the row space in between the, the crop rows, so you want to consider where the roots are. Spread of the canopy is another factor because it limits access to the field by equipment. And maybe broadcasting or application through an irrigation system might be more appropriate later in the season. Soil fixation is another consideration, and overall economics may drive the farmer in one direction or, or the other. But just keep in mind that the cost of applying a fertilizer is one, one factor if we are applying in a fashion such that we're not as efficient as, as possible with fertilizers than potential problems with losses of those nutrients and environmental negative environmental impacts may come about. Here's some equipment for applying fertilizers in a in a band application method. Essentially, all of these pieces of equipment consist of some mechanical way of opening the soil so that the fertilizer, either liquid or dry fertilizer, can be dropped a little bit below the soil surface. The two pieces of equipment in the top use a disk coulter, it's called, to cut a slit in the soil and then a knife follows that and drops the, the liquid fertilizer in that slit. The orange machine in the bottom is a planter, and it is set up to apply dry fertilizer alongside of the rows of seeds as the seeds are being planted. No-till systems warrant a little bit of discussion because they're very popular, particularly here in the United States. And there are, are a couple issues in terms of fertilizer placement with these systems. I want to just introduce you to these aspects. For those of you that are experienced in this area, you'll understand. For some of you that are just learning about these conservation tillage practices this may be interesting information for you to follow up on. There's a lot of research in this area, and I would encourage you to, to followup and learn more about fertilizer and fertilizer management in these conservation tillage. Because, remember, most of these cases we're not tilling the soil as much as we used to. And so, getting the fertilizer where it needs to be in the root zone might be more of a challenge in these production systems. And there are two aspects. One is the, the stratification of nutrients like phosphorous and potassium if we're just applying them on the surface, as we would with a broadcast application. Also, the decomposition of the organic matter residue on top contains nitrogen and phosphorus and potassium. And as that material decomposes, those nutrients are more or less left on the, on the surface or very near the surface. So, in these situations most scientist and most of the research is pointing to banding and getting that fertilizer below the root surface in no-till systems. And there has been equipment developed to do this without disturbing the crop refuse on the surface, because remember, in these conservation tillage that's sort of the hallmark of these production practices, maintaining as much organic matter and crop residue on the surface. The other aspect pertains to nitrogen losses in surface-applied scenarios, as you would with no-till. And this is mostly due to nitrogen volatilization. We're already mentioned this with certain nitrogen products that may be more subject to losses or to volatilization when they're placed on the surface. The other aspect with nitrogen is immobile, immobilization, and we learned about this, in our nitrogen, fates and transformations lecture. As microbes are degrading and decomposing in the organic matter, if that organic matter has very little nitrogen in it, those microbes may use nitrogen that we might supply by fertilizer to help them grow and, and develop the population of microbes to further decompose the organic matter. So again, for these reasons pertaining to nitrogen efficiency, scientists generally recommend now in most conven conservation tillage or no-till systems to band the nitrogen below the surface. This is typically done with what's called a coulter and, and a knife system. I've given you a picture here, identified the coulter and the knife. The knife follows the coulter and injects the fertilizer in that slit behind the opening that the coulter makes in the soil. And in most of these no-till or conservation tillage practices, this is the way farmers are applying or banding fertilizer in those systems. So again, I just wanted to point out to you in some of our systems where we've encouraged farmers to move more towards soil conservation practices, the development of the technologies that go along with fertilizer application has, has had to be, be researched out. There's a lot of information on how to do conservation tillage and fertilizer practices, for example, we haven't even touched on how to use soil sample in these kinds of systems where you band the fertilizer. So again, I just wanted to raise your attention bring your attention to this particular topic and encourage you if you're interested in it, whether you're a large farmer or a small farmer, practicing conservation tillage to, to investigate with your local or regional experts and resources on how best to, to practice the highest efficiency with regard to fertilizer management in those production systems. I just wanted to mention here also manure, a lot of us are interesting in using manure, remember, when we talked about poultry the poultry industry on the Eastern shore of Maryland when we talked about the Chesapeake Bay. And along with trying to develop best management practices for manure management has come along some interesting technologies. Manure, as you can imagine, presents challenges for broadcasting it or spreading it out on the surface. And that's what we used to do in the old days. I remember as a, as a kid spreading manure, poultry manure with a, with a manure, a regular manure spreader and that put the manure on the surface. Typically, we would incorporate it by plowing or disking. But as you move towards no-till or reduced tillage kinds of practices, then leaving the manure on the surface might not be the best the best option. So, along has come some technology, in this particular case, liquid manures for injecting that material much the same way you would with liquid fertilizers. So, we can get more efficient with our manure applications in this manner. And also, as a side benefit, we can minimize some of the odor problems associated with broadcasting manure. Just to mention again, some of the challenges with manure utilization as a, as a fertilizer material the low analysis of the major nutrients is a challenge with manure. And that involves just the, the econ, economics of moving that much material that is relatively low in, in nutrient content. Manure also contains phosphorus, so we do not get the choice of leaving the phosphorus out, if we're using manure to supply a significant portion of our nitrogen for example. Manure can be expensive to apply. Those machines that inject liquid manure are expensive to purchase or to, to rent and if we don't incorporate or inject the manure into the soil, then it's subject to run off particularly if we're putting fertilizer out in the winter time and then we have the snow melts and the rains of the spring. And so, losses of the nitrogen from volatilization or perhaps even denitrification with manure would be a question. So, those are all issues that you would want to find out about or learn more about if you're contemplating using manure on your farm. The other aspect in the three, in the four Rs is the third one and that's right timing. Ideally we would like to put the fertilizer out just at the right time when the crop is going to take those nutrients up or most likely to require those nutrients. And this is best because that would be radically be the most efficient way to use those nutrients. We would be putting them out exactly at the time when they are going to be taken into the plant and do us some good in terms of yield. And that's why that would be the best from a theoretical standpoint. But obviously, it may not be practical to do it exactly in that fashion. So, we'll talk a little about some of the, the strategies that science has brought to the farming world, in terms of timing of fertilizer applications. If you can kind of picture in your mind the way plants grow, most plants this sort of sigmoidal approach, where in the, in the very beginning of the crop, it's slow. And then, the growth rate picks up. And you know this if you've grown crops. They reach this phase where they're growing very, very rapidly. And then, they might reach the fruiting stage and things slow off, and then eventually, maybe even decline a little bit. So, on this particular curve here, growth response, this is where we would want to start applying may be in split applications fertilizer during this rapid growth phase. And so, how can we do that? How can we time the fertilizer so that we're catching that crop when it has its greatest need? So, split applications is the term that we apply to this aspect of timing. And under a split application approach, we're taking the amount of fertilizer that we know the crop is going to need for that season and we, we talked a little bit about when we, when we discussed soil testing, how we come about with that amount of fertilizer. And then, we might have portioned it out during the season so that we can put out a smaller amount several times during the season. So, this obviously has some positive impacts on nutrient efficiency and we have less risk of losses of nutrients if some of our nutrients are still in the bag so to speak. But we have to balance this aspect of split applications with cost because it does cost more to particularly take a piece of equipment across a field several times during production seasons, during the production season. I just wanted to point out though, that if we can maximize the timing and we can do it in a minimal number of trips across the, the field, then we've probably maximized several of the factors, the economics in particular. And also, possibly, the environmental aspects because the fertilizer is there for the crop to take up and less is there in the field for leaching or runoff losses. And just to point out that improper timing can be just as big of a problem as not having the right rate of fertilizer out there. In fact, they're probably, basically the same, the same thing. So, we want to make sure that when we're thinking about timing, that we put the, the fertilizer out at the optimum time and that we're able to get into the field to do these actions. Split applications can be achieved in several different fashions, we've already shown you the, the so-called coulter and, and knife approach for putting liquid fertilizers out. Fertigation is another maybe new term for some of you, applying fertilizer through the irrigation system. And we can do this with center pivot irrigation systems or with drip irrigation systems, and I'll show you how, how that's done. There is also an interesting tool that was developed here in Florida a couple decades ago, actually, for injecting fertilizer through plastic mulch and I'll show you that, that piece of equipment. And then also, some would consider split application through foliar means as another way of getting nutrition to the crop. This mainly applies to nutrients like the micronutrients that are required in very small amounts through the season. Here's a, here's an example or a, a depiction or a diagram of drip irrigation system. In this particular system here, you can see, here's the field with the crops and the drip irrigation tubes are laid out. Here's the red line or main line that's bringing the water to the, to the field and then back here, we have a fertilizer tank and an injector that's apportioning fertilizer from the tank and injecting it into the water stream that's coming into this field. So, this is what we call fertigation or injecting fertilizers from a stock tank, and mixing it with the water that's going out to the, to the field. And as you can imagine, a scenario like this is very inexpensive. Once you have the system already in place for delivering water, it doesn't cost a lot more to also be able to inject fertilizers and this would be much more efficient compared to a system where you're actually having to take piece of equipment through the field multiple times during, during the season. So, this is fertigation applying fertilizer to a crop through the normal irrigation water or irrigation system. Here's an example of a fertigation with, with tomatoes. As you can see, here's our, our growth curve again. And in this particular case this is a recommendation that we use here in Florida for growing tomatoes on plastic mulch. We put a small amount of the nitrogen, this is for nitrogen put a small amount of nitrogen in the, in the bed and I'll show you a picture of that in a minute. And then we've divided up the week during the, the growing cycle, and we put out varying amounts of fertilizer. So, we start out with small amounts early here. And then, you can see that the rates increase as we go through go through the season. And then at the end of the season, the rate of application actually declines a little bit. So, this would be an example, a real example of how farmers growing tomatoes with plastic mulch could schedule their fertilizer. Here's a video of the way the setup would occur in the field. You can see the plastic mulch beds, in this case, it's zucchini squash growing. And I'm showing you the drip irrigation tube that comes from the mainline and follows alongside of the row, under the plastic mulch. That drip irrigation tube then, would take the water and the nutrients out, and apply them. And you can see that, given the fact that we're under the mulch, those fertilizer nutrients are protected from rainfall and leaching. And also, they're being applied right in the, the root zone during the season. So, it's a very efficient way of managing water and nutrients particularly for those intensively grown crops like vegetables. Here's an example of a center pivot applying water and this particular center pivot could also apply fertilizer through by injecting it into the water and it would be uniformly applied as the irrigation water is applied. Here's a center pivot with a fertilizer tank and it's being injected into at the pivot point. And that fertilizer will travel out through the center pivot and be applied through those nozzles. I've mentioned here that these systems to apply fertilizers must have, by law a what's called a backflow prevention system. And so, this is a set of mechanical devices that are applied, that are installed in the irrigation system and they prevent that fertilizer from moving backwards. So, you can imagine if you're injecting fertilizer through the system and for some reason, the pump stops and the water starts to, to travel backwards and back down into the well or the water body. So, these backflow prevention devices help keep the nutrients from traveling backwards back into the water devices back into the water system. And they're very, very important and required by law if you're going to be injecting nutrients through the irrigation system. It would be true for a center pivot or for a drip irrigation system. I've mentioned foliar applications as a way of split applying or applying fertilizers through the season. This mainly applies to nutrients that aren't needed in large amounts in the crop. Foliar application might not be able to supply enough nitrogen and potassium, for example through the season by this means but it's very effective for many other micronutrients. So, here's a leaf surface and it has been wetted by a solution of micronutrients and water sprayed on the, on the surface. Here's a sprayer that might be applying micronutrients to the surface of this hay field. Foliar applications are most effective, as I said, for those nutrients like micronutrients that we need in very small amounts to overcome deficiencies. So, for example, you might be growing tomatoes in a soil where a micronutrient like iron or zinc might be tied up in the calcareous soil or the high PH. Well, foliar might applications of these nutrients might be a way to bypass the fixation that can happen in the soil, and it can be a very effective way of supplying micronutrients during the season. Here's an interesting device that was developed awhile back here in Florida, particularly for those plastic mulched beds where drip irrigation was not used. Remember, we talked about subirrigation on the spodosols irrigating the, the soil, irrigating the crop from below from a raised water table. In this particular case, fertilizer is banded in the bed before the mulch is applied. And these liquid fertilizer injection wheels are very neat tools for injecting fertilizer, liquid fertilizer through the plastic mulch. So, these wheels roll down the, roll down the rows, poke a little hole in the plastic inject into the soil, maybe a couple inches deep liquid fertilizer. They're particularly useful for scenarios where you're double cropping. So the first crop is produced on the plastic mulch. You'd cut the, the crop refuse off of that mulch and you reuse that same bed and that same mulch. And so, fertilizing for that second crop can be done very effectively with these liquid injection wheels. So, if you take home lessons for when we talk about timing and placement of fertilizers, I want to just remind you that these two aspects of the four Rs can be just important as the first R that we talked about, the right rate. The objective in all of this is to get the right amount of fertilizer available to the crop at the right time so that we minimize waste of fertilizer and the farmer gets the, the highest return on investment for the dollar spent on the fertilizer. And when we do a good job of selecting these three Rs then we can minimize the chances that we're going to lose fertilizer to, to the environment. We talked about the fact that for most efficient use, applying the fertilizer as close to the plants as possible in and around the, the root um,zone and also at the right time during, during the season. So, there are some aspects that we need to consider when we're managing those nutrients. And we provided some things to at least think about you know, if somebody is thinking about a certain production system or switching to a production system, thinking about fertilizer management is very, very important. Fertilizer not used by the plant is a waste input that costs money and in today's more environmentally conscious world it could represent losses to the environment, which we all are very careful about minimizing.
