What is variable-rate fertilizer application?

We share how you can benefit from basic precision farming technology and how to start applying it in your field.
Usevalad Henin
Usevalad is an expert in GIS and agricultural chemistry. He has been developing precision farming tools since 2013. He is also the co-founder of OneSoil.
Variable-rate fertilizer application allows you to apply different rates of fertilizer in each part of the field. How you distribute fertilizer depends on the planned yield, soil fertility and factors that influence it. This might be topography, soil texture, electrical conductivity, as well as soil nutrients and moisture content.
Variable-rate fertilizer application allows you to apply different rates of fertilizer in each part of the field. How you distribute fertilizer depends on the planned yield, soil fertility and factors that influence it. This might be topography, soil texture, electrical conductivity, as well as soil nutrients and moisture content.
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Why it's used

All fields are heterogeneous. Soil fertility and yields across a single field are always different. In our experience, there have been cases when the difference in yields of several plots within one field reached 400%. As such, plants in different plots reacted differently to fertilization.

If you use a uniform fertilizer rate in a field like this, there could be excess nutrients in some areas and a deficit in others. As a result, the fertilizer's efficiency will be low in some parts of the field.

When applying variable fertilizer rates, we take heterogeneity into account and determine the exact fertilizer rates for all areas of the field.
Карта с точками отбора по сетку 0,28 га_Блог OneSoil
You can easily tell how homogeneous a field is by its yield. For instance, over here, the yield values in some parts of the field differ by 8 times. But you can't apply a uniform fertilizer rate in a field like this.

The benefits of variable-rate fertilizer application

Nutrient balance. All areas of the field receive the necessary amount of fertilizer.

Potential increase in yields. More efficient fertilizer doses make increases more likely.

Save on the amount of fertilizer used. Avoid overspending in areas where nutrient removal is low.

What you need to start

A tractor with an onboard computer and a spreader capable of changing rates during operation. First off, you'll need to load a prescription map to the onboard computer using a flash drive or a modem. Your tractor will get the GPS location and will be able to adjust the fertilizer rates as it moves through the field.

Self-propelled or trailed sprayer and a seed drill. They can be used instead of a fertilizer spreader. Our experience shows that they're even more accurate than spreaders because they can switch rates faster.

Prescription map. You can create this map in the OneSoil app.

What could go wrong

The onboard computer will not be able to 'read' a prescription map. Prescription maps are created using special software. Sometimes their format may not be compatible with the onboard computer. But this is a rare occurrence. The most common file formats are shape and iso xml. They are supported by almost all onboard computers' manufacturers. If a file doesn’t work, you can convert it to the desired format.

You may choose the wrong fertilizer rates. No matter how you apply fertilizer, it’s important to inspect your field in good time. If you skip this step, the results of fertilizer application will be unpredictable. To avoid that, you should inspect your field and set the proper productivity zones. These are the areas where the relative yield remains stable from year to year. You can create productivity zones for your field for free in the OneSoil app.

Equipment won’t switch to the required fertilizer rate immediately. The fertilizer spreader usually changes the rate by approximately 20 kg per 100 meters. It depends on the speed of the spreader and the type of fertilizer. If you need to apply less fertilizer in a particular area, this is likely to be difficult. Unfortunately, there aren’t many ways to avoid it. All you can do is buy a spreader that applies fertilizer more accurately or you can just accept the status quo.

What to read next


Experiment conducted by Usevalad Henin
Map created by Nastia Zenovich
Text edited by Tanya Kavalchuk
Article layout by Anton Sidorov
Calculate fertilizer rates with OneSoil for free!
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Usevalad Henin
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