A standard soil analysis is done on a volumetric basis. Scoops, of a fixed volume, are used in measuring the soil for analysis. The scoop size is based on an assumed average volume, which equates to a typical soil weighing two grams.
Logan Labs uses a 2-gram soil scoop for the standard analysis package, as well as nitrate and ammonium and all extra parameters that are provided on our standard soil report.
When using this scoop to sample a soilless medium, the result will be lighter than two grams. This will cause the concentration of nutrients in your sample to be underestimated.
To adjust for this, a scoop weight of your soil-less media will be determined and reported on your standard soil report analysis as a percentage of a standard two-gram sample. You must request a scoop weight of your soil-less media on the worksheet.
Soil scoops and sample weights are not included in the process for a saturated paste analysis. A volume of approximately one cup of medium is saturated with deionized, or client’s water.
It is recommended that a soilless medium be evaluated by both a standard soil analysis and a saturated paste analysis.
Pour Through Technique
Periodic monitoring during a growing season is easily done by using the pour through method. This method provides a non-destructive sampling technique. The desired frequency differs by crop. Weekly measurements are recommended for short term crops and for plants being fertigated.
Pour Through Procedure:
1.Irrigate the crop thirty minutes to one hour before taking the sample. The key is to be consistent.
2.Place a saucer under the container.
3. Pour enough distilled water on the surface of the container medium to yield approximately 50 mls (2 oz) of leachate onto the saucer. The amount of water added will depend on container size and media characteristics.
4. Collect the leachate and pour it into a sample beaker or vial. (Contact the lab for sample vials.)
5. Send the sample to laboratory with the appropriate submission form.
The laboratory will report the results within 24 hours of sample receipt.