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Take the guesswork out of your fertility plan with soil sampling

Read Time: 3 minutes

By Erin Meyers September 27, 2023

Wouldn’t it be helpful to know exactly what exists within your soil and what is needed to grow a healthy crop? Luckily, soil sampling can do just that, so why don’t more farmers do soil sampling every year? Testing your soil can provide a clearer picture of what is happening beneath the surface, allowing you to discover the exact nutrients you need to help your plants thrive. 

How it works

Samples are taken at two different depths in your field. The first depth, at 0-6 inches, is where phosphorous, potassium, and most micronutrients are present. The second depth, at 6-24 inches, is where you will find nutrients like nitrogen, sulphur, and chloride which are measured across the entire depth due to their characteristics of moving within the soil. These samples will provide guidelines on the amount of nutrients that are present in the soil and what nutrients are lacking as well as any other issues that may be present. Taking samples to see what lives in the soil of each of your fields will better help you when making fertilizer decisions.

What lives in the soil will make all the difference

Soil pH plays a crucial role in how nutrients interact with plants. If your soil has low pH, this means higher acidity. This can make it easier for some elements and heavy metals to be more readily available to the plant. On the other hand, low soil pH can allow other nutrients to become chemically bonded to each other due to the acidity, making them completely unavailable to the plant. This nutrient-soil interaction can cause a toxic reaction to the plant by providing it with too much of one nutrient and not enough of the other. This type of situation results in an unbalanced nutrition for that crop which is what you want to avoid.

Potassium and chloride also play a very important role in soil test results. Potassium is very abundant in Saskatchewan soils, resulting in most producers not adding potassium to their fertilizer blends. However, Saskatchewan soils are becoming more and more deficient in chloride. Chloride helps with photosynthesis and plays an important role in developing plant cells. So you can see how this deficiency could reduce plant productivity, resulting in lower yield. The most efficient way to make sure chloride is available to the plant is by adding potassium to your fertilizer blend. Potassium and chloride go hand in hand and need to be looked at together in your soil test to get a broader picture of what your soil is lacking.

Nail the proper timing

I highly recommend you begin soil sampling as soon as your crop has been harvested. There’s been uncertainty around this timing in the past as it was commonly believed that waiting until later would give better results due to the straw having time to break down and release N back into the soil. Research has shown that it takes much longer for this process to happen in a way that converts N into a usable form for future crops. Knowing this, it is better to sample as early as you can before the ground freezes. It's also easier to get a clean-cut sample right after the combine because the ground is not as compact as it would be if harrows or a spreader had been over it again. This allows for a much more even sample depth to be obtained.

Sampling year after year shows a trend in the soil and how those nutrients move, or don’t move.  This trend allows for more precise fertilizer planning to take place.  It opens the door for in-depth conversations not only around macronutrients but also micronutrients and how they play into soil health and yield.  Applying a blanket application or same blend across the whole farm no longer makes sense and is not environmentally friendly, nor is it economical. Applying a custom blend per field or even per crop will be far more beneficial to your bottom line as you will be providing your crops with the nutrients that they need.

If you have any questions about soil sampling or fertility planning, contact your local Cargill agronomist.

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Erin Meyers

Erin is a Market Development Agronomist for Cargill out of the Raymore/Wynyard/Balcarres locations and farms with her husband and his family near Kelliher, Saskatchewan. Erin grew up on a family farm where her passion for agriculture was born, and went on to graduate from the U of S with a Bachelor of Science in Agriculture. She strives to help growers make good agronomic decisions and loves supporting them in becoming more successful in their own businesses.