Adding a new layer of precision to your variable-rate programs

What are Yield Zones?

Yield zones are areas of a field that have a certain yield trend. If an area of a field typically yields lower than others, it is a low yield zone, and if an area yields higher, it is a higher yield zone and so on. Based on these trends, you can create an accurate estimate of what each area can yield, and then assign a yield goal to that zone.  A map made from yield zones can be very helpful when determining how best to apply fertilizer and plant seed across your field.  In this article, we will go through how yield zones can take your precision ag practices to the next level.

Yield Zones and Fertilizer

Is soil testing enough?

Variable-rate fertilizer application is quickly becoming the norm. It took awhile, but most farmers can now see the benefit of applying more or less fertilizer in specific parts of the field based on real data on their farm. It’s practical, after all. The odds of having the exact same fertility levels on every acre of your field are nearly zero. It makes sense, then, to give more attention to the less fertile areas of the field, right?

While that may be the case in some fields, it isn’t in every field. You see, simply using soil tests to determine the fertility of an area of a field doesn’t tell you the whole story. For instance, we know that clay particles are better at holding on to nutrients in the soil than silt loam, but not so good at letting them go. This is why a soil test might show an area of the field with a large amount of clay content with high nutrition and deceive you into believing that this is a high-yield potential area. Except that it isn’t, and you know that because year after year that area does worse than others.

This is why variable-rate fertilizer, while more precise than flat-rate, is not nearly as precise as your fertilizer application can be. Technology keeps moving forward and so will precision ag, but there’s something you can do right now to add another layer of precision to your variable-rate fertilizer application: adding yield zones.

How Yield Zones Improve Your Practice

Here are the basics of how your fertilizer prescription is made:

Soil-building fertilizer + maintenance fertilizer = Your fertilizer prescription

The soil-building fertilizer portion of the equation accounts for the fertilizer that is required over a certain number of years to raise the soil test levels to the desired level. The maintenance fertilizer portion is the fertilizer required to account for this year’s crop. Both aspects of this equation have a deeper and more complicated equation associated with it, but we don’t need to understand all of that to know how yield zones help. The maintenance fertilizer portion is the only part that the yield zone affects. The maintenance fertilizer is calculated by taking the yield goal of this year’s crop multiplied by the crop’s removal rate of the nutrient we are adding fertilizer for. Without any added yield zone data, the equation would assume a flat yield across the entire field (a yield, by the way, that someone might have chosen without any real data to back it up).

So, when adding a yield zone to the maintenance fertilizer portion of the equation, you are essentially replacing the flat yield goal with a variable yield goal based on real data on each area’s potential yield.  This way, you can avoid the trap of adding too much or too little fertilizer on an area of your field that yields differently than others.  Practicing this will make you more efficient with your fertilizer and money over time, showing economic and agronomic dividends in the future.

Yield Zones and Planting

Variable-rate Planting

Variable-rate planting is where yield zones truly shine. There are few other options, if any, to help decide which parts of your fields should be planted with a higher or lower population. Simply put, if an area of the field is prone to yield higher, then it would make sense to plant that area at a higher population. Unlike with fertilizer, there are no complicated equations to insert this data into. You can simply break your field into different yield zones, create a yield zone map, and set your population rates according to that map. Deciding on what rates to use will be at the discretion of you and your seed salesman because every hybrid is different and responds differently to higher and lower populations. But once you have that part figured out, you need only to create your prescription by assigning planting populations to each yield zone.

Multi-hybrid planting

Much like variable-rate planting, yield zones can help with multi-hybrid planting as well. You may have heard seed hybrids described as “workhorse” or “racehorse” hybrids before. This simply means that the hybrid was built either to respond better to worse conditions or to better conditions. For instance, if a workhorse hybrid was built to do well with low moisture, you might want to plant it in clay-heavy soils that have trouble retaining moisture. But if you were planting in an area that could retain its moisture and exchange nutrients well, you would want to plant a racehorse hybrid and capitalize on that yield potential in a way that the workhorse just couldn’t do. Conversely, that racehorse that did well in the richer soil would do much more poorly than the workhorse if planted in a higher clay area.

I think you’re probably seeing where this is going by now. If a planter has multi-hybrid capabilities, then it would make sense to put the racehorse hybrid in the high-yielding areas and the workhorse in the low-yielding areas within the same field. That is where a yield zone map would be invaluable.  If you know an area of your field is constantly yielding lower than the others, you could then infer that this area is a stressful environment to plants, relatively speaking. Adding the workhorse here and the racehorse to your better areas makes a whole lot of sense. Of course, you will need to use more data and checking to ensure that the reason for your troublesome areas can be mitigated by the right hybrid.

How Can I Start Using Yield Zones?

To start using yield zones you will need to gather the appropriate data to create them. We will be releasing an article here next week that will go through the different popular methods of gathering that data, as well as give you guidance on how to choose which method is right for you.

In the meantime, if you wish to learn more about how all this works, you should speak to your precision agronomist at Service and Supply Cooperative. Service and Supply is at the forefront of precision ag, and we are always using the most advanced methods of making your farm more efficient. We are already creating a large number of variable-rate prescriptions using yield zones, so we have ample experience using this method and can attest to its effectiveness.  Use one of the contact links below to get in touch with your local Service and Supply branch to take your precision ag to the next level.