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The Value of Precision Soil Sampling


You can have the most award-winning field out there, but if you can’t have an encore performance every year, it’s a one-hit-wonder. A huge part of how well a farm prospers is down to the soil. Regardless of what crop you grow, they all need balance to thrive. While the surface can provide some indication of soil health, it doesn’t tell the full story. After a harvest, there are often lingering questions. Do you have enough nutrients in your soil to produce a healthy yield? Was your soil pH off? How much of your potassium leached due to the rain this year? Those are valid questions and can all be answered with the right soil samples. Soil sampling can answer those nutrient questions, flag changes in soil fertility, allow you to be proactive about what you put on your fields, and save on your bottom line. How? That is where precision soil sampling comes in.

In the past, the primary objective of basic soil sampling was to determine the average nutrient status and nutrient variability of an entire field. While precision soil sampling also has these two objectives, there are some modifications, the most significant being that producers are interested in areas within a field instead of an entire field. Within that focus, they study how trends in soil fertility are related to other field properties. Meaning, how soil type, overall topography, cropping history, and general fertilizer management all interact and impact a field’s health. However, even with modifications, precision soil sampling still uses the basic principles of soil sampling. 

Zone vs. Grid Sampling

It’s an ongoing debate about whether zone or grid sampling is the best method for collecting soil samples (and both have pros and cons). For zone-based soil sampling, you first need to determine how you’ll create your zones. You can base zones on various factors, such as historical yield data, soil electrical conductivity (EC), aerial imagery, etc. In basic terms, EC is a measure of the amount of salt in soil and is a vital indicator of soil health. EC mapping has gained popularity because it’s a relatively inexpensive way to gather high-resolution spatial data on the soil. Mapping soil EC adds time in the field before soil collection can start, but it’s a way to capture soil variability, so the zones you create have similar soil characteristics.

Due to the need to take more soil samples within a field, grid-based soil sampling can be more expensive and time-consuming. The sizing of the grids can also vary based on the farm. While the most common sizes are one or 2.5-acre grids, farmers also use 4.4 and 10-acre grids at times. Intensive grid sampling could be particularly insightful if you are looking to establish the base points of a field’s soil health and establish zones based on those insights. Soil variability can be captured by creating grid sizes that are smaller than the size of typical zones. Even though grid sizes are smaller and you must take more samples, you save time by overlaying a grid on the field and immediately sampling.

Answering Your Soil Nutrient Questions 

While soil sampling is a valuable practice at any time, it’s especially useful during periods of lower commodity prices. Testing data will provide the information you need to create a smart fertility plan. By understanding what nutrients are already in the soil, you can make more informed decisions about what fertilizers and tank mixes you need to add and where. That can be especially important in sustainability practices. The more balanced you can make the environment for your crops, the more yield you can expect. After your soil samples are analyzed, your soil report’s data will be an in-depth analysis of your soil’s attributes.

Flagging Changes in Your Soil Fertility

A common practice in the farming community is to have soil sampled every three to four years. However, soil samples taken more than a year ago will have limited value. Even though soil fertility is an essential factor in row crop production, many farmers only have a general idea of their soil nutrient values. Overlooking this step can cause a loss in crop production and unnecessary fertilizer applications. If yields have consistently increased or decreased by even a few bushels since the last time you sampled, the information for next year’s crop is outdated. Increased yields require and use more nutrients, while decreased yields require less.

Because soil nutrients change from year to year, you can’t use the same products and rates on every field and expect to experience consistent yields farm-wide. Your farm’s fertility program is far too large of an input for you to be confident about what’s required for one year and then make assumptions over the next two to three years.

Being Proactive With Your Data

Data is only as valuable as the insights it enables. In a recent presentation, the USDA said that we are “drowning in information while starving for wisdom.” Their statement is a commentary on the need for people to take their data, put it into digestible amounts of information quickly, and then use it to make informed decisions. In soil sampling, data not only provides insights into past performance; it also ensures that you proactively catch potential red flags. Red flags could include imbalances in nutrients, soil pH, organic matter, and more. 

For example, we had a client that typically sampled every four years. After discovering that potassium was a limiting factor on his farm, he spent the next two years focusing on building potassium levels. We began working with the farmer in year three of his four-year cycle and collected soil samples as part of our information gathering process. The farmer had done such a good job that there was now excess potassium in the soil, which was beginning to affect phosphorus absorption negatively. Without soil testing data, he would likely have applied more potassium that year, which would have been an unnecessary expense and negatively affected yield.

What happened on this farm is easily representative of similar situations on any farm from year to year. Sampling every year allows farmers to access reliable data and take the guesswork out of planning. If you suspect certain nutrients are limiting in the soil, sampling every year will provide the answers. You can implement changes in a more timely manner and utilize the soil as a real investment.

Saving On Your Bottom Line

In prior years, perhaps it made sense to build up soil nutrients across the farm. These days, farmers need to find ways to control the budget and lower production costs. When you conduct soil testing every year, you eliminate guessing. You can know for sure if you need to reduce or increase inputs, especially across different fields. Applying seed and chemicals at the same rate across every acre can reduce yields, lead to excess purchasing of unnecessary chemicals, and increased labor costs.

There has been much debate around zone vs. grid sampling, what using precision ag tech on a farm actually means, and even what nutrients are vital to the farm’s health. But, what is clear is that taking regular soil samples will help you make informed decisions. So no matter what sampling method you choose, make sure that it’s the method that best fits your farm’s needs.

  • Crop Management
  • Farm Management
  • Farm Planning
  • Soil