Sample handling, laboratory submission, and analysis
To ensure accurate soil test results, composite soil samples need to be correctly handled and submitted to the laboratory. Generally only a small amount of the soil that was collected needs to be sent to the laboratory for analysis.
Mixing, handling, and laboratory submission
After collecting soil samples from one sampling zone, the samples should be mixed thoroughly to create one composite sample. If samples are still in cores from the sampling probe they should be broken up. Once the soil has been mixed, collect about 0.5 kg (1 lb) of soil place it in a container, such as a small bag, and label it with the sampling zone, depth, and date collected.
In the field, samples should be kept cool and out of direct sun. If nitrate (NO3-N) analysis will be completed, samples should arrive at an analytical laboratory within 48 hours of sampling. If samples will not arrive at a laboratory within 48 hours, then they can be spread on paper to air dry for 2-3 days at room temperature before shipping. Samples for basic soil fertility testing do not require air drying and do not need to arrive at an analytical laboratory within 48 of sampling. However, soil samples that are air dried may be stored at room temperature and kept long-term as reference samples that can be sent for analysis at a later date.
If samples were taken for a basic soil fertility test (0-15 cm), a general or basic soil analysis should be completed. Depending on the laboratory, nitrate (NO3-N) may or may not be included in basic soil analysis. A nitrate analysis should be requested for samples taken to the 15-30 or lower depths if sampling for PHNT (Figure 1).
Figure 1. Soil testing packages to request if completing basic soil fertility and NO3-N analyses simultaneously.
The following laboratories provide soil analysis:
More soil sampling topics: