Ryan Flaming: Fall soil testing of hay fields and pastures

Ryan Flaming

Soil testing can be done in either spring or fall on hay fields and pasture. Given a choice, fall would be the preferred time because it allows more time for any needed lime applications to have an effect before the main growing season begins, and it gives the producer some flexibility for planning nutrient applications.

Soil sampling on a regular basis (every three to four years) can keep you from applying excessive and unnecessary amounts of fertilizer or manure and can increase yields by revealing exactly which soil nutrients are too low for optimum productivity. By doing this practice properly, producers can save money and reduce environmental impacts.

To take accurate soil samples, it is best to use a soil probe. You can borrow a probe from many county Extension or NRCS offices. A shovel or spade can be used, but make sure to dig a hole first and then take a nice even slice to the correct depth. A shovel or spade that angles to a point at the bottom can easily result in misleading soil test results because the sample is biased by having more soil from the surface and less from lower depths.

When taking soil samples, it is important to have a representative composite soil sample from the field by combining several soil cores and mixing thoroughly. Ideally, one composite soil sample should represent a uniform and treatable area and should not exceed 40 acres, and for more variable fields, no more than 10 acres.

On these areas, take 15 to 20 cores or subsamples to make up your representative composite sample. If the field has areas where different forages or crops have been grown, or has different soil types, then soil sampling from these areas should be done separately.

Sampling depth for pastures and hayfields should be 3 to 4 inches for pH evaluation. For phosphorus and potassium, a 6-inch depth is preferred when submitting samples to the K-State Soil Testing Laboratory since that is the depth, we have used to calibrate recommendations.

— Ryan Flaming is a Kansas State Research and Extension agent for Harvey County. Agriculture is his specialty. He can be reached at 316-284-6930.