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What i have learned (and what every farmer should know) part 1

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  • What i have learned (and what every farmer should know) part 1

    I know that the subject of fertilizer spreading is not one that too many people invest a lot of time thinking about. But I have been operating a fertilizer spreader for going on six years now and I have stumbled on some things that I don’t believe anyone really realizes. By anyone I’m not just talking about growers but the fertilizer industry as a whole. I feel justified in saying this because everything I am about to tell you I have had to come up with on my own. If what I am about to say is being utilized other places why hasn’t it trickled down to places like here? Why wouldn’t it be common knowledge within the fertilizer industry as a whole? If someone out there reads this and can say definitively that they know about and utilize this process which I am about to detail I would love to hear from them.

    I want to make it clear that I am talking about granulated fertilizer. The machine I operate is a Case-IH floater with an 810 Air-Box spreader. However the method of delivery is not of great importance; it’s the process by which it is delivered. Even a pull-behind spinner spreader can be accurate if done properly.

    When I first started running a spreader no one could set me down and show me specifically how to go about making the machine do what I would consider a satisfactory job. There seems to be this misconception that when we see one these, high dollar, computer controlled, GPS guided, state of the art machines out in a field that the farmer is getting a good spreading job. Perhaps they are but chances are far better they are not. Or perhaps I should say that they are not getting as good a job as they could be or should be. It has always struck me as odd that, given how large of an expense fertilizing is, growers seem so willing to trust what is actually happening out in the field. Probably more than any other farm machine out there none is more dependent on the skill of the operator than a fertilizer spreader. I’m not talking about putting the machine through its mechanical paces. That is definitely a skill that is taught and has to be learned but after that comes the real challenge; how to get the machine to do what it is designed to do; which is to take a given quantity of fertilizer and spread it uniformly over a given area as specified on the paperwork. These machines are capable of being very precise but it’s not as simple as punching in a couple of numbers and expecting the computer or the machine to take over and do the rest. Getting one of these machines to be precise is what has captivated my interest. It then becomes a game that is fun and worthy of being played. It is also necessary because only by being as precise as possible are you giving the grower what he is paying for and expects. Every time I pull into a field to start a new job my goal is to be perfect. The fact that it is practically impossible is what makes it so fun.

    I hope that I have piqued the interest of whoever is reading this enough to keep reading because now I want to get into the specifics of what I am talking about. When I am given a spreading job the main focus for me is the application rate which is given in lbs per acre. These machines think in lbs per acre so that is what I as an applicator think in as well. The chemical analysis and units of nutrients per acre for each specific fertilizer, which is represented in the blend, is what the grower is concerned with. It is important to me as well but in a different way, which will become clear as we go along. It also needs to be understood that by acres I mean machine acres since of course that is all the machine knows. These machines have the ability of being calibrated to count acres accurately but that doesn’t mean that the machine acres are going to match the job acres every time. In fact that happens very seldom. So when I say that I can set my machine to be precise what I mean is that I can put the lbs per machine acre at the exact rate that the job calls for.

    When a spreading job is created it is broken down into equal batches by weight which is determined by how much one tender truck can hold. So a job can be anywhere from one batch to any number depending on the amount of acres to be covered and the lbs per acre. That can vary from as much as a hundred lbs per acre or less to eight hundred or more. Most tender trucks have at least two separate compartments and may have as many as four. This enables us to divide a batch into at least two separate jags. The blender at our plant has the scale built into it so this allows us to stop the transfer process from blender to truck at any point and document the number of lbs remaining in the blender. The truck is then moved and the remainder is loaded into the second compartment. Now it is a simple matter of subtracting the number written down from the amount of the whole batch to arrive at how many lbs are in each compartment. There is no need to try and make these amounts even. In fact it is better if one is smaller than the other. All that is important is that it is known how many lbs are in each jag. This is what we call the split. Every time a truck comes to the field the driver has the split with them. Therefore every time I take on a jag of fertilizer I know; within ten lbs; because that’s the smallest increment that the blender can measure; how many lbs are being taken on. Knowing how many lbs I have on is the key to being precise because now I have the ability to track it.

    Before I explain what I do with this knowledge I want to explain how these machines are calibrated. As I said earlier, these machines cannot set themselves. Every time a new job is started the operator has to go to a place on the computer called product control. On one of the sub-screens is where three variables need to be entered. The first is lbs per acre, which is given on the paperwork; very straight forward. The next is density, which is arrived at by taking a sample weight with a small hand held scale as the product is being loaded onto the spreader. The third variable is called the spreader constant. It is this setting that is the other key to being precise. This setting is represented by a three or four digit number. All three of these settings affect the speed of the belts delivering the product to the booms and into the tubes to be blown onto the field. The spreader constant is an arbitrary number that over-rides the other two settings allowing the operator to dial the machine in. Knowing how to properly control the speed of the belts so that they deliver the prescribed lbs per acre is the whole key to being accurate.

    Unless someone can prove me wrong, it is my understanding that the general consensus in the fertilizer industry is that there is one spreader constant setting for straight UREA and another for blends. The number would only vary from machine to machine because since there is a computer controlling the mechanics it only stands to reason that no two machines would be alike. In my experience this idea that one constant setting fits all is completely wrong. The reason it is wrong is because of the nature of fertilizer itself. Fertilizer has what I like to call a variability factor. If that isn’t already a term then I am coining it. The variability factor of fertilizer is quite high. There are a number of factors that affect these variances; size, shape, cleanliness or dustiness, density and humidity all play a part. Some of the things contributing to these factors are who made it or its source, how many times it’s been handled, etc.

    Darby Dahl
    Fairview, Montana

  • #2
    Part 2
    I suppose the obvious question then becomes; what does that have to do with anything? The short answer is everything. The long answer is everything I am about to tell you. This variability factor directly affects how easily the product comes off the machine. It actually comes into play every time the product gets moved but it only becomes evident when there is a way to track it and measure it. The thing is, it only really matters at the most critical time; when you are trying to spread a given amount uniformly over a given area. Straight urea is actually is the most variable of all the fertilizers and it is the one most commonly applied on its own. Imagine how much easier uniformly round, smooth, dust free urea would roll off a machine compared some that is irregular and dusty. This is why you can’t lock onto one constant setting and expect favorable results. You can only lock on for each individual job, not for the rest of time. It was the machine itself that revealed this to me after I started doing what I do. In fact I was actually trying to find that one number and failing miserably when it dawned on me that there is no such thing. That constant number has to be found with every new job.

    Ok, now let’s get back to spreading. The reason it is important to know how much product is taken on each time is that it allows the operator to create a target. You can figure out how many acres should get covered by the amount given. For example; let’s say in an imaginary job that the application rate is 482 lbs per acre and I have just taken on 8,580 lbs. 8,580 divided by 482 comes to 17.8. That is how many acres I should cover, so that’s the target. At this point I would enter the constant number most likely to make the machine achieve that target acreage. This number isn’t just pulled out of the air; well it kind of was at the beginning but in time it is reached through trial and error and documentation. I keep a journal of every job I do. I enter the date, the blend, the density and the constant number I ultimately end up with on that particular job. I categorize these jobs by using the first number of the blend, which is urea. For example let’s say that the blend for this job is 160-80-25. I have a place in the journal dedicated to all of the blends beginning with 160. Over time I have acquired a catalog of all the blends I have done. Now when I start a job I can refer back to that blend or one similar and it will give me a constant number that may not be exactly right but will be very close. It gives me a place to start.

    After I have settled on a constant number I then open up the job and begin the spreading process. I spread every bit of that jag of fertilizer off. All except for a very small amount that is left on the delivery belts so that they don’t have to be recharged. This probably doesn’t amount to much more than five lbs. I am then able to compare the target acres; which was 17.8; to the actual acres covered. If it was right on or within a tenth of an acre either way I would leave the constant where it is and repeat the process with the remainder of the batch. Let’s say that this is a two batch job at 21,500 lbs per batch. That would leave a remainder of 12,920 lbs. Doing the same math as before I should cover 26.8 acres with this jag. Now let’s say I missed the target acres of the first jag by 4 tenths of an acre and actually did 18.2 instead of 17.8. If you do the reverse math and divide 18.2 into the 8,580 lbs, you come up with a rate of 471 lbs per acre. That is eleven lbs per acre less than what was prescribed. So you can see how being off just a few points with the constant can affect the rate significantly. To correct that I would increase the constant by two points and repeat the process. If the first constant setting was; let’s just say; 680, I would set it to 682 which would hopefully increase the belt speed just enough to close the gap.

    Making the adjustment to close the gap is important because the further you go with the job the further off target you will get. The four tenths I was off on the first jag would very quickly turn into an acre or more by the end of the second jag of the first batch. By the time I was done with the second batch it could very easily be three or more acres off. That is unacceptable to me. I like to use the analogy of sighting in a rifle. If your scope is off by a quarter of an inch at 25 yards how far will it be off at 100 yards? Nothing short of dead on is acceptable when sighting in a rifle and I subscribe to the same principle with spreading fertilizer. The problem with this analogy is that every time a new job is started with a different blend it is like dropping your rifle on the ground and knocking the cross hairs off. You are back to square one.

    Perhaps a more apt analogy is to think of the constant setting as radio dial and all of the blends as having their own frequency. It is the operator’s job to find the right frequency for that particular blend. That is not to say that different blends can’t have the same constant because some do. But you aren’t going to know that until you go through the process. However it has been my experience that there is usually some difference between most blends. It may only be one point but it’s often more, and that makes a huge difference. Straight urea, as I have alluded to earlier, is even worse. I have had to make as high as 30 point adjustments because the plant started taking out of a different bin that came from another source. That is why you can never trust it and why documentation is so important. I realize all of this takes some effort but the payoff makes it all worthwhile. As I said earlier this is the game that holds my interest and makes me want to keep doing it. When I have found the magic number for that blend on that day then I am the one in control of the machine, the fertilizer, and the outcome of the job.

    The outcome of the job is one of the main reasons I go through this process every time no matter how big the job is. It is the best way of tracking the job. There are times on larger jobs that I will do one full batch before checking where I am at but never more than that. Knowing how much product I am taking on is very beneficial when approaching the end of a job. It gives me the ability to make last minute adjustments that will benefit the outcome. Knowing exactly how many acres I am going to end up doing is never certain. Getting the map acres; which are created on the computer in the office; to match the machine acres is difficult at best. We have been working on it though and have gotten considerably better at it in terms of consistency. It is never a certainty however. There are ways to determine how many acres are left. If the remaining passes are equal in length I just note the number of acres in one pass and multiply by the number of passes left. The sooner I can do this the better because if a rate adjustment is required the amount would be less and spread over a larger area. If, for example, I am down to my last full batch and I know how many machine acres are left, all I have to do is divide those acres into the batch size to get the new rate. It also allows me to build in a buffer so that I don’t come up short. Coming up short is time consuming and costly. I consider having a hundred lbs or less on the machine at the end of a job as being about as perfect as one can hope for. There are times though when a job will, for whatever reason, get away from me and I end up with what I would consider an unfavorable outcome. To me that only confirms how tricky this can be. But at least I can say that I am trying each and every time. Another thing that affects machine acres is overlap. Doing a job in which no overlap occurs is very rare. It is mitigated to some degree because these new machines are equipped with the ability to shut off half the boom at a time. I don’t want to get sidetracked on the subject of overlap so I will just leave it here.

    Another aspect of this whole thing is the emerging popularity and use of variable rate applications. Knowing the proper constant setting for a particular blend becomes absolutely necessary because that is the only control you have over the outcome of the job. All rate changes are controlled by the program that has been uploaded into the machines computer. There is no way to track the job because the rate is constantly changing making it impossible to know how many acres should be covered by any given amount. Having a catalogue of blends with corresponding constants for that machine comes in awful handy. It is my contention that companies are reluctant to get into variable rate applications because they don’t have favorable outcomes.

    I want to point out something about the computers on these machines. When the machine is in use and actually doing the job of spreading, the screen will have a place that shows target rate; which is the lbs per acre entered for that job; and actual rate. Both of these readouts will match pretty much all the time. The thing is it doesn’t mean anything if the constant number isn’t accurate. I could set the constant number to half of what it should be and the computer screen would still show the actual rate as corresponding to the target rate when in fact it would be applying half of what should be applied. I’m just pointing that out in case someone wants to point to that as proof of accuracy.


    • #3
      Part 3
      It must also be pointed out that since every machine is different, every machine has to have its own data. Every operator must keep a journal on the machine they are operating and that journal needs to stay with the machine to be used and added to by anyone else operating the machine.

      Everything I have been talking about in this article has been field tested, field proven, and is demonstrable. In fact I extend an open invitation to anyone who has read this, and is willing to give me an hour of their time to seek me out and allow me to demonstrate how I go about doing the job of spreading fertilizer.

      In conclusion I just want to reiterate that it is the high variability factor of fertilizer that makes all of this necessary. If I am wrong in thinking that no one else is doing what I have laid out in this article then by all means speak up, because I want to know.

      Darby Dahl
      Fairview, Montana


      • #4
        Nice article Darby - Nice to see someone that tanks pride in there work ! This comes from a former Spreader Guy - But I got my start in the mid - 70's ! No GPS - No computers - lol But the funny thing - it has not really changed much from then to now - same things - but just different equipment to work with .

        Back in the mid 70's - We tape on the mirrors to help us keep the right distant from the last pass - we also weighed all material - but had to take into consideration the soil as to if it was hard ground or fresh worked - in the soft dirt it would pull harder and had less ground speed - which would - if not figured in would add to a over applied app .

        Many things can affect rates - equipment wear - you name it - it all factors in - spreading and doing a good job is a art ! + science ! For me - or really new app driver - after you get that first season under your belt - then you learn your equipment - both pros and cons - then the on spot jobs come easier and more consistent + know the fields and the farmers you work with - there is ALWAYS a few - lmao here that will forget a few acers in a field - then you come up a little short - After a few years or this - I just refigured the rate to the acers I had come up with and the funny thing ? I came out on target - lol

        I always - always - enjoyed spreading and spraying at that plant , many moons ago - Hope you enjoy yours the same - Like you said - it is a game - to figure out all the un- knowns and then come out right !

        Have fun and thanks