Soil Testing Program
GCA is dedicated to helping you realize the maximum value of your crop, not just your fertilizer investment. This can only be achieved if we understand your soil environment and its critical values. Soil sampling is the best way to determine the needs of the crop and help you develop a targeted plan to meet your yield goal. Sampling will help you determine if there are any other factors inhibiting your yield potential.
Why grid sampling and not zone or composite soil sampling?
First, let me say that any method of soil sampling is better than not sampling at all. However, each method has benefits and limitations. So, lets briefly discuss the three main sampling philosophies.
- Composite is where a sample to be analyzed, hopefully comprised of 10-15 core samples, is randomly taken on a whole field basis. This sampling method represents an average value. For example, one area of a field may have a pH of 4.9 and another area may be 7.8. Averaged together, the value may look like pH 6.3.
- Zone is where soil samples are taken based on soil type or CEC (cation exchange capacity). Each major soil type in a field, determined by the EC (electrical conductivity), is sampled and has its own analysis. This method is much better than composite. However, variability in a given soil type can still exist.
- Grid sampling is a good option to capture more field variability. Each grid point is GPS referenced and the core samples are taken in a 30-40 foot radius around that reference point. Each grid has its own analysis and is essentially treated as its own field. Common grid sizes are 2.5 acre, 5 acre and 10 acre. It is important to note that larger grids produce more sampling error. That is why Garber Cooperative utilizes 2.5 acre grids as the standard grid size.
In an ideal world, I would prefer to grid sample within defined EC's of a field. This would produce the most accurate representation of the field.
pH: Amending the soil pH is the single most beneficial thing we can do to raise overall productivity on the farm. This is especially true when we are rotating to crops other than wheat. Wheat breeders in our region have adapted wheat to tolerate fairly acidic soils by selecting varieties that can tolerate soluble Aluminum. However, most other crops that we grow are more sensitive to acidic soils. This represents a potential cropping dilemma. For example, legumes and brassicas are much less suited for low pH soils and generally do not produce as well in those soil environments. Fact is, we do not know until we sample.
Factoid: pH is a logarithmic function of how much Hydrogen is present in the soil. So the difference between 7.0 (neutral) and 6.0 (slightly acidic) is a factor of 10. Whereas, the difference between 7.0 and 5.0 is a factor of 100.
Agronomist perspective: When considering making amendments to a low pH soil, remember that only products that contain Carbonate have the ability to reduce acidity. This is due to a chemical reaction that occurs when the Carbonate reacts with Hydrogen. Hydrogen is pulled off the soil exchange sites by Calcium or Magnesium in the liming material and reacts with Carbonate resulting in CO2 and H2O. Thereby, lowering the free Hydrogen in solution which in turn reduces soil acidity.
When soils are at near neutral 6.0-7.2
- The vast majority of soil nutrients are soluble and considered more available to plants
- Increases the Nitrogen Use Efficiency
- Enhances soil microbial activity and survival--enabling the soil to cycle nutrients more efficiently and increase nodulation potential on legumes
- Eliminates the toxicity of Aluminum and Iron in the soil
- Allows certain herbicides to work more effectively
- Reduces overall plant stress and increases comparative yields
Garber Cooperative is your resource for Precision Grid Sampling and Interpretation of Analysis
- Sampling on 2.5 acre grids allows us to determine the areas of variability and make precision amendments to the soil. Lets us put the inputs where they are needed, in the amounts needed, to minimize the field variability
- Our sampling services provides you more analysis for the dollar than our competition
- pH, Organic Matter, Phosphate, Potassium, Sulfur, Calcium, Magnesium, Manganese, Zinc, Boron, Copper, Sodium, CEC and Base Saturation
- We typically do not test for Nitrate-N with our 2.5 acre samples, however, can add this to the package for an additional cost
- Mobile Nutrients, (Nirtrate, Sulfur, Chloride, Boron) are best sampled at depth