When should I test soils?
For years, fall soil sampling was the standard practice. However, it became a challenge to collect samples, get a lab report, develop a recommendation and apply nutrient needs prior to tillage or winter. In some situations, if the summer and fall were extremely dry, fall sampling could provide somewhat of an inaccurate measurement of true plant-available nutrients. As a result, a more modern method is to collect samples during the spring or early summer, which allows for greater time to develop an actionable plan.
Should I GPS-track sample locations?
In any science-based system, it’s always important to collect as much location data as possible. Leveraging GPS to track each sample location allows for site-specific treatments (variable rate) and for specific sites to be retested in future years to track progress.
How should samples be taken?
- Collect random cores across a field, entered as one sample
- This is the cheapest option to get an idea of field fertility levels. However, this method only provides an average and doesn’t disclose areas of highs and lows. This method could provide a false sense of fertility security.
- Acre Grids
- There’s no question that a grid method is more effective than a random core sampling pattern. However, this system only works when fields, soil types, drainage or even organic matter change in the field along straight and defined lines. As most would agree, nothing in nature has naturally straight, defined lines. Therefore, this system is better than some options, but does leave room for improvement.
- Management Zones
- In modern production agriculture, a lot of management styles or systems have moved to management zones. These zones are similar beyond just physical location (Lat. & Long). They can be based off organic matter, water-holding capacity, elevation or yield (from yield maps)—i.e., high-, medium- or low-yielding environments. These zones can be based on any number of these variables and can differ between farm operations.
At the end of the day, Illinois producers farm in acres or sub acres and the more fine-tuned the information can be, the better the potential plan of action can be implemented. For more details, it’s always good to attend winter agronomy meetings to learn about new concepts or to partner with a local CCA who understand local needs and challenges and who can provide a modern recommendation.