Soil Sampling in a Wet Spring – Yes, It’s Worth the Challenge

Dave Braaten

Manager of Agronomy

Valley View Ag Services, LLC

The extreme weather conditions last fall and this spring resulted in many fields not being soil sampled. The timing to accomplish this task is narrow this spring, but worthwhile. Guessing on the soil nutrient levels and fertilizer requirements can be costly with either excess applications or under applications depriving your crop of reaching its full potential while maximizing inputs. Sampling of wet soils can be challenging but will be rewarding.

Picture of a hand soil sampler — *Hand probes* still remain an effective method for collecting samples.

If conditions do not allow for hydraulic soil sampling equipment, hand probes still remain an effective method for collecting samples by foot or ATV, with soil analysis results available within 24 hours. To eliminate lost time from the discarding of poor quality, partial soil cores, head to the field with WD-40 at your side. Make sure that you use the brand name to lubricate the probe and not generic lubrication products as WD-40 has been tested and proven not to contaminate your sample results. Do not use vegetable oil lubricants as microbe activity will affect nitrate levels in your sample.

Rust-free equipment is a must-have

Not all probe designs perform the same in wet, sticky soils. The preferred probe tip is typically one with a recessed lip, which allows for added space inside the probe tip, reducing plugging. Your sampling equipment must be rust -free. Also, avoid using galvanized or brass equipment to prevent additional contamination. If you need to acquire the proper soil probe, contact your soil lab specialists or sampling equipment vendors to access the recommended equipment.

Pull your soil samples before spring tillage

Photo of an ATV Soil Sampler from Amity Technologies — *ATV mounted automatic hydraulic soil samplers* can collect multiple samples at a time, letting you cover your fields faster. And its smaller, lighter platform allows sampling of all types of soil.

Several soil sample methods can be used, including grid, zone and composite. For simplification, this blog focuses on composite sampling. If fields have not yet been tilled, try and pull your soil samples prior to spring tillage for better control of sample depth. Smaller fields will typically improve the accuracy of your averaged composite soil sample. Composite samples consist of 15 to 20 random cores per field that are thoroughly mixed in a clean, non-contaminated plastic pail, avoiding non-representative areas of the field. A smaller sub-sample can now be used to fill your sample bag. In wet soil conditions, 0-24” samples are the easiest to obtain. Have a tape measure handy to ensure you’re sampling at a 24” depth. Bag your samples separately from 0 to 6” and 6-24.” Sample bags and labeling instructions are usually available from your designated lab. If you’re submitting soil samples for nitrate-N analysis, be sure to keep them on ice in a cooler to stop microbial changes and deliver them to the lab immediately.

A successful soil probe unearths valuable information

By exercising these standard soil sampling methods, producers can successfully determine valuable information in a short period of time in order to maximize returns this growing season.