Using Technology to Direct Better Soil Sampling

As harvest winds down for many of us, it is time to start thinking about next year’s crop. Now is a great time to consider taking soil samples to help make the best agronomic decision in regards to fertilizer application and planting for the next growing season. Establishing good soil health is critical as it can make or break how next year’s crop will turn out. Depending on your crop and soil conditions, sampling can be done in variety of ways. There are many tools to determine what the best route to take is and technology offers an assortment of options to help you get there, from composite sampling an entire field to a more rigorous site specific project involving multiple samples and multiple depths.

Here are just a few resources that can be used to direct how to soil sample a field:

•     EC Data (Electrical Conductivity) – Sampling based on EC zones can allow you to minimize the amount of samples needed to really dial down specific soil health issues. EC data can correlate nicely with things like soil texture and salinity.

•     Imagery – Imagery is a great resource to help identify and diagnose problem areas in a field. NDVI (Normalized Difference Vegetation Index) imagery is an image that shows how a plant reflects and absorbs infrared light during the photosynthesis process. Once a field has been analyzed, it allows us to locate specific areas of stress that can influence plant growth. Irrigation, plant disease, nutrient deficiency, soil variability and insect damage are a just a few examples that can have an influence on plant vigor. By using NDVI imagery, strong and weak areas can be targeted. This can help to create a sampling scheme based on specific areas. In most cases multiple images can be used to determine where changes occurred.

• NRCS Soil Map – A simple way to go about soil sampling can be done by using a NRCS Soil Series Map. This map can give you an idea of what the soil type and properties are throughout a specific area in a given field. By sampling different soil types, you can determine how the soil is impacting your crop.

• Yield Data –Using yield data can be a great way to guide sampling.  Yield data is often considered a ‘report card’ for fertility programs and crop performance.

At the end of the day, the amount of samples taken will help you make the best decision for how to move forward for next year. The real story can only be told after ground-truthing each of these tools so it is important to keep in mind. The more data you use the more confident you will be in your amendment decisions. Remember, no two fields are the same so it is important that you decide what mode of action is the best route for your farm and your budget.

- Christina White, Precision Ag Specialist