Harvest is well underway in many areas, but before you call the season quits, consider doing your soil sampling.

Penn State University agronomist Douglas Beegle says fall is the best time for this because it gives you more time to sample properly than springtime, and you have time to think about the results and make plans for the next season.

Here are some things to keep in mind when soil sampling this fall.

1. Decide when to sample in the fall.

According to CanolaWatch, the ideal time to take fall samples is when soil temps drop below 44 F, as the microbial processes in the soil slow down and mineralization is minimal. But if you’d like to evaluate whether this season’s crop had enough nutrients, then take samples immediately after harvest.

2. Collect many cores.

Kansas State University Extension recommends taking at least 10-15 soil cores from 2-4 acres to minimize effects of soil variability. Taking 20-30 cores may provide more accurate results.

3. Follow a zigzag pattern, or take cores in a radius.

Following a zigzag pattern is better than a planting pattern to minimize any past non-uniform fertilizer application effects, says Kansas State. If you’re sampling grid points for variable-rate nutrient application maps, collect cores in a 5- to 10-foot radius around the center point of the grid.

4. Test surface pH.

Penn State University Extension says no-tilled fields, as well as those in pasture or alfalfa, should have a sample taken at a 2-inch depth to check the surface pH, as repeated surface nitrogen (N) applications can result in acid soil.  

5. Stay consistent.

Your sampling depth, time of year and locations should be consistent in the future. This way when you get your results, you can look for trends, says CanolaWatch.