A Short Guide to GPS Grid Sampling

A Short Guide to GPS Grid Sampling

Soil testing is an essential practice for modern farming. The samples produced through testing allow precision ag specialists and agronomists to determine nutrient quantities and create a customized recommendation for the producer. Soil sampling simultaneously cuts the cost of inputs and helps optimize yield. There are a few common management systems used to sample a field, but MKC uses GPS grid soil sampling.

GPS grid soil sampling overlays a defined size grid to place GPS soil sampling points across a field to provide the foundation for accurate soil nutrient mapping.  These grids can range from one to five acres, but 2.5 acres is the standard size.  The results are then inputted into crop nutrient equations to create variable rate prescriptions based on each fields’ individual needs.  Prescriptions can be generated for about any nutrients, but the most typical are nitrogen, phosphorus, potassium, zinc, sulfur, and lime for correcting low pH.  

MKC Precision Ag Specialist Craig Miller says grid sampling is the best practice to reveal field variability. “The biggest advantage of grid sampling is the amount of data it creates. If we do 2.5-acre grids on an 80-acre field, that means we have 32 data points to look at,” he said.

The primary use of grid sampling is to determine if any nutrients are a limiting factor on yield, so the producer can solve the problem before it affects the intended crop. Other forms of sampling fall short in finding the limiting factor. The other methods break a field into zones based off yield data or satellite imagery, and the zones created are individually managed. But, the zones can vary significantly in size and performance, even within the individual zone, so the grower may not learn the actual cause of their performance issues.

Ross Benisch, precision ag specialist for MKC, added grid sampling provides the best value for the amount of data produced. “With grid sampling, we are addressing each nutrients’ needs independently, making sure it is not a limiting factor in the field which is the primary goal behind any fertilizer program,” he said.

While 2.5-acre grid soil sampling is the standard at MKC, other types are also used based on the situation and the producer’s requests.

“We recommend producers grid sample every four years, but zone sampling can be a good choice to look at fertility situations in the non-grid sample years or certain nutrient management areas within that field, a good example being carry-over nitrogen,” Miller said.

Because of the ability to determine specific needs at a reasonable cost, grid sampling is the preferred choice for MKC. Producers interested in learning more about grid sampling should contact Precision Ag Specialists Ross Benisch or Craig Miller, or their strategic account manager.

Written by: Mikey Hughes, MKC communications intern

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