A lot of soil sampling is done in the fall, and according to extension agronomist Daniel Smith, it is the right time to collect this information.
“For soil sampling, it’s a really exciting time of the year,” said Smith during a University of Wisconsin-Madison Nutrient and Pest Management Program video. “We want to measure how many nutrients are left over in the soil because it is our savings account for the next crop to grow.”
Smith recommended testing for phosphorus, potassium, soil organic matter, and pH levels. “That way, we can allocate nutrients for next year’s crop via manure application now or in the spring, and then we can think about purchasing the fertilizer to supplement those nutrients,” he explained.
A sampling plan should be created by looking at a map of the farm and determining what crops are going to be grown where. Smith said that collecting one sample for every 5 acres is the broad standard, but many people will pull more samples than that, working with 2.5 or 1 acre grids.
“Soil samples take such a small amount of soil off of the landscape and are used to base our recommendations on and next year’s profit and success on,” Smith reminded, “so we need to be as accurate as possible.”
He said that sampling depth is important. The appropriate depth is based on tillage or the conservation system, but he said in Wisconsin, 6 inches is typically adequate for most farms.
Smith noted that farms should also be thinking about timely manure applications in the fall. He said to apply manure when soils are not subject to compaction or environmental nutrient losses.
In summary, he reiterated the value of filling that soil savings account and having a plan to do so.
“Sticking to that plan, or just making minor adjustments, is really important for success,” he noted.