MCSE: Baseline Soil Sampling

Soil cores are taken at 5 sampling stations per plot. Soil cores (2 cm dia.) are taken within a 2m radius of each station flag to a depth of 25cm. An equal number of cores are taken within row and between row when row crops are grown. All cores from one plot are composited in one sampling bag. A standard sampling consists of 2 cores at each station. Forested sites are collected by one person at the same time the main site is being sampled by 4 others. If 5 people are not available the forested sites may be sampled in the afternoon while soil from the main site is being sieved.

The soil is brought to the lab and sieved through a 4 mm screen to remove debris and to homogenize the soil sample. Each treatment has a designated screen in order to reduce contamination between treatments. Latex gloves are worn when sieving and mixing the soil.

Field moist soil is stored at 4 C until the determinations are completed. All samples, except the April sample, are disposed of at the end of the year. The April sample is air-dried and archived.

Mineralization potential may be assessed as the difference in nitrate and ammonia values from the initial sampling and an “incubated” sample. Incubations are performed on a subsample of the initial composite sample which is placed into a gas-permeable plastic bag and buried in the plot from which the soil originated. Incubation length is 21 days. This is done once per year, typically in July. (Details here: MCSE:Short-term N Mineralization Potential).

Materials

• Printed bag labels
• 8×4×18 Plastic sampling bags
• Sharpies
• Butter knives
• Site maps
• Soil probes (bucket augers when too dry for probes)
• Buckets
• Latex gloves
• Tote Trays
• Brush
• 4 mm mesh soil sieves

Procedure

1. Label plastic bags with appropriate information about the sample (e.g. project, date, plot, variate). Cover labels with clear mailing tape to secure label to bag and to protect against moisture.
2. Prepare sampling buckets. Each bucket should have the following: site map, sharpie marker, butter knife, sampling bags, and soil probe.
3. Take samples to 25 cm at each of the 5 sampling stations. A butter knife is helpful in removing soil from the probe. In cropped systems, take two cores per station, one in the row and one between the row. Take the same number of cores from non-cropped systems. Composite all samples for one plot in one plastic bag.
4. When soil conditions are too dry to allow for sampling with a push probe then a bucket auger can be used.
5. Tie the sample bag and place in the alleyway to be picked up when the sampling is completed. All efforts should be made to complete sampling in all plots on the same day.
6. Take a core at the edge of the next plot to clean the soil probe. This will reduce contamination between plots.
7. Continue sampling each plot in the same manner until all have been sampled.
8. Pick up soil samples and return to field lab.
9. Separate soils by treatment.
10. Wear latex gloves while sieving. Sieve each soil sample using the 4 mm mesh soil sieve labeled for that treatment. Sieves are stored in the field lab.
11. Sieve soil into a plastic tote tray. Return sieved soil to the plastic sample bag. Discard rocks and large organic matter remaining on the screen.
12. Brush sieve and tote tray clean.
13. Change latex gloves after each treatment.
14. Place soil samples into 4 degrees C refrigerator.