Tips For Spring Soil Sampling

Testing the soil nutrients and other values in your field is critical for making the right decisions on fertilizer application.  Soil test recommendations are calibrated to a certain depth, so time your sampling for accuracy. Wet or very dry soils can make it tough to pull out cores by hand and result in an uneven sampling depth. 

Dan Kaiser is an extension nutrient management specialist at the University of Minnesota. He says the size of an area to sample depends on the variability of the field. It’s also important to take enough cores.

"And this is one of the things that we see a lot of corners being cut on just because of time," says Kaiser. "One of the issues we see with imposing a significant amount of variability comes from taking too few cores. Typically, we see 6, to maybe 8 cores taken per sample, what we really like to see to get a good average is more like 10-15, and really, over 15 there’s not much of an advantage at that given point."

Avoid testing fields too soon after applying fertilizer or manure. This can lead to severely inflated results and overestimate the availability of nutrients.

"With manure it’s a bigger issue. If say we applied it one fall, I wouldn’t really want to take that sample until the next fall, until you’ve had one cropping year between that fertilizer application and when that soil sample is taken," he says. "It just gives it time to react, gives it time to start to stabilize so you get a more accurate result."

There are many options for having your soil analyzed. Look for those that provide relevant data for your area.