General soil sampling procedures and guidelines used by BCS, LLC
Soil Sample Location
Each sample should represent a uniform soil area with similar past management. It is recommended that each sample represent 10 acres or less. Sampling areas should be determined by the soil type, soil color, topography, drainage, past management of the field, manure applications or presence of livestock and productivity. Maps of soil electrical conductivity (EC) and GPS yield maps can aid in distinguishing between field areas with contrasting soil properties or crop nutrient removal.
Consultants should use field observations at the time of sampling to determine which local site factors should guide their sampling pattern within each field. Soil survey maps, GPS yield maps, bare soil images and input from the farmer as to past land use (fence rows, pastures, building sites and old field divisions) can be used to create geo referenced zone maps of these factors prior to soil sampling to help guide the consultants sample locations in combination with his or her field observations.
Soil sample zones should be recorded via GPS or geo referenced maps to insure location and repeatability of sampling. This also aids in refining the sample zones as more information becomes available about the field or soil and allows the zone to be used as part of a directed nutrient application (VRT) program.
Sampling Depth, Collection and Frequency
Soil sample probes should be taken to the depth of the furrow slice (6-7 inches) or modified based upon tillage practices or the lack of tillage (no till) for the farm. Each sample should consist of between 10 and 15 cores with cores being collected in a zig zag method thought-out the sample zone. Each core should be examined prior to placement into the sample bag to insure that it conforms to color, texture and depth for other samples in the management zone.
Each soil sample should be air dried and all cores in the sample should be ground and thoroughly mixed prior to submission to the laboratory for analysis. Doing so insures that each sample is truly a representation of the sample area.
Soil samples should be collected on a regular sampling interval based upon crop rotation, fertilizer or manure applications, or tillage practices. In many instances under high management it would be appropriate to sample fields every year. Fields with high test levels or fields receiving manure should be tested every year. In other cases sampling every two years under a corn-soybean rotation or under a bi-annual fertilizer application would be appropriate. No more than three years should elapse between sampling intervals.