How much detail do you know about the soils on your farm or ranch? Do you know the productive potential, nutrient status, or special limitations of the "back 40?" In the July issue we listed some points to consider when deciding where to fertilize and how much to apply. Those of you that have attended an NF Grazing School or New Cooperator Seminar have heard a discussion about doing a soil inventory. A soil inventory is simply an organized method of collecting and listing selected properties and potentials of the different soils contained within the boundaries of your farm or ranch.
In order to do a detailed soil inventory we must first determine the soil series or mapping unit and determine the nutrient status of each major soil on the farm. The best tool for determining the soil series is a county soil survey available from your local Natural Resources Conservation Service (formerly SCS). From the survey we can determine soil series, capability unit, adapted crops or forages, expected yield, and special management or limitations.
Once the soil series and/or production areas have been designated on a map, soil samples should be collected to determine soil pH, nitrogen, phosphorus, potassium, and possibly other nutrients. Soil nutrient levels will help decide the amount of fertilizer and lime (or other treatment) required to achieve the potential yield.
We use a form to list Field Identification, Soil Series, Capability Unit, Acres, Adapted Crops/Forages, Expected Yield, Range Site Description, Expected Range Production, and Soil Test Results. The information on these inventory forms can be utilized to estimate total forage production from the ranch or to help make decisions about which crops to grow on certain sites.
If you want to be able to make more precise decisions about the management of specific fields, I would encourage you to utilize aerial photos or sketches to record small areas within field boundaries that have different production than adjacent areas. If the soil series is the same, different production may indicate different nutrient status or a need for some special treatment.
Any of our Pasture and Range or Soils Specialists can answer questions about doing a soil inventory.