As we approach winter and colder temperatures, determining the current fertility of pastures and alfalfa fields through soil sampling is a critical step towards optimizing production next year. Sampling now, before the ground freezes, can help with planning this winter and give time to develop a fertility plan if soil tests show fertilizer is needed.
The process for taking soil samples is straightforward. Pull 10-20 cores at a consistent depth of 8 inches for every 40 acres sampled. These samples can be taken in a representative area of the field or arranged by soil type and topography. Mix the samples together and take about a pint’s worth out to send off for analysis.
Soil cores and recommendations are often based on cores taken down to 8 inches. However, if previous samples have been taken at a different depth, such as 6 inches, continue with the consistent historical depth and adjust accordingly by communicating your actual sampling depth with your soils lab to assure accurate fertilizer recommendations.
Due to mineralization, soils have more nutrients readily available nearer the soil surface; so deeper sampling depths can dilute the samples and increase nutrient supplement recommendations.
Keep in mind that soil sampling may not reduce the overall amount of fertilizer needed but will help ensure appropriate application rates, which can result in a better yield. Additionally, moisture is the most limiting factor in pasture and alfalfa production, not fertility. You can apply all the fertilizer in the world but doing so in a drought won’t help plants grow. Fertilizer applications on dry land areas, especially for nitrogen, should be based on expected moisture. — Samantha Daniel, Nebraska Extension
