How to Calibrate a Tractor-Mounted Fertilizer Spreader

How to Calibrate a Tractor mounted Fertilizer Spreader

Spreaders must be accurate, else the fertilizer will be incorrectly applied. Pesticides, grains, herbicides and other types of spread can lead to adverse reaction with your yard if either too little or too much fertilizer is applied There is a bevy of ways you can go about calibrating your fertilizer spreader—check them all out here:

Can you recall the last time you performed a calibration on the fertilizer spreader you use? The dangerous thing about absconding this crucial step is you will be wasting a great deal of time and resources during your fertilization sessions. If you are wise, or we lucky enough to be advised by a wise agricultural professional, then you probably already have your tray kit and a calibration kit. If you don’t have one, ensure you get one after reading this article. They cost around $250.


Regardless of the kind of spreader you use, whether broadcast spreaders or a drop spreader, you’ll need to get a couple of things for your calibration:

  • Measuring scales
  • Tape measure
  • Big jar, jug or mug

For good measure, you can also throw in set of pegs, chalk, or garden strings, but this not mandatory. Okay, let’s begin, shall we!

Step 1: Calibration Area

First things first your work is to establish the area of calibration. Through mathematical manipulation, it is easy to estimate the essential covered width of coverage. You multiply this by the length your spreader is meant to be pulled during the entire calibration procedure.

Step 2: Amount

The next step is to determine how much material should be delivered to the calibration area. This is performed by utilization of a ratio called the known-product-application-rate. So if the rate of application of our desired product happens to be 4 lbs. of spread per every 1,000 square feet, the known-product-application-rate ratio is established as follows: Assume the amount of unknown product is y and it lies on upper side of the right-hand position: when you cross-multiply it, you are left 6 pounds of spread needed for 3,000 square feet. What this means, then, is that 6 pounds is your preferred amount of spread material which is needed to be collected from your calibration area.

Step 3: Checking Overlap

Before you start applying the fertilizer on your calibration area, you are required to consider the existing amount of overlap. You will be doing the calibration using a single pass; completion of the real application should be expected after several overlapping passes. What this means, therefore, is the real rate of your spreader output ought to have its level modified due to overlap.

Take, for instance, if the overlap you are dealing with is 100 for all six passes, your middle pass ought only to deliver half of the intended rate of application since 25 percent additional spread fertilizer being delivered by each adjacent pass. In the above scenario, your spreader ought to be set to disburse 3 lbs. pounds of fertilizer material per 1,000 square feet. This will ensure a rate of 1.5 pounds per pass, plus 1.5 lbs. for each overlaps the sides giving a sum of 6.0 lbs. of fertilizer for every 1,000 feet squared after all applying is completed.

Step 4: Delivery

Your last step will be to get your spreader to disburse the specifically accurate amount of spread to the area calibrated. If you own one of the spreaders that spin or rotate, you can make your work easier by draping a plastic tarp around your hopper in order to enclose its impeller. This will force the distributed spread to fall on to the bare earth within the area of the hopper’s width. This is will be greatly beneficial to you since it will significantly reduce the number of minutes of hours it will take you to sweep and gather the spread which you will weigh. Also, it will significantly elevate the accuracy of the whole procedure.

Step 5: Weighing & Calibrating

After dispersal of your spread material, the next step is collecting it and weighing it. You must be careful to ensure that you minimize the amount of contaminants you collect while and maximizing the amount of material recovered from all of the material. You will achieve an accurate spreader setting when the weight calculated is all recovered (give or take 10 percent). The next thing to do is to subtract the amount of spread you have remaining from the amount you started with. Only on doing this can you establish whether your current spreading speed is too slow or too quick. In the event that you find that your current rate was faulty and unsustainable, you have no choice: you have to redo the test only this time with the distribution setting altered to either a lower or higher level. Repeat the whole process until—and only until—you attain the right spread rate level. It’s a kind of tedious extrapolation, but don’t worry it works. When you’re finished and the process is a success, ensure that you take note of your correct rate of spread so you can refer to it in the future.


Calibrating your spreader is a crucial and vital stage of spread application. In the case that it is mishandled, when you apply granular or liquid spread, then it becomes impossible trying to establish whether or not the application is being done at appropriate proportions. Sustained misapplication of product could very directly lead to unexpected response, damage to the machine, product failure, or even some unseemly amalgam of all three problems. Studies on the agricultural mechanics surrounding calibration have consistently reported that the rate of application, as well as the density of the spread bulk rate, can significantly alter the distribution and delivery patterns of your spreader. Your spreader should be calibrated, as a rule, every time the hopper products are changed or any time there is a significant increase or reduction in the rate of spread application. If you take into consideration the potential cost of repairing physical damage, of labor and material, the cost of calibrating your spreader is too marginal, too insignificant, an activity given the benefits and prevention it offers.



About Seth 58 Articles
Hey, Seth here! As a homesteader and self sufficient farmer, my main interests are in gardening, tree care and lawn care. There is nothing I appreciate more than having a beautiful and healthy home garden. I spend most of my days gardening, caring for my small orchard and a few animals that I keep. I thoroughly enjoy working on my garden as well as sharing tips and experiences with people who have the same passion. My education in environmental science and technology has also led me to explore agriculture from a different perspective and exchange information with people from around the world.

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