Physical Soil Testing
Dispersion Testing (test for Calcium need)
To test the dispersing capacity of the soil, take dry soil crumbs of about 0.5 cm (1/5 of one inch) and place into a petri dish that is filled with de-ionized water. Distilled or rain water is OK, but de-ionized results in the most accurate test. It is important that the water be in the petri dish before the soil crumb is put in it and the test remains undisturbed from any kind of movement during the testing period.
The dispersion test is viewed over a period of 2 hours. The recording is at 10 minutes, and at 2 hours. Look for total dispersion of the soil (separation of clay particles) at those two times.
Soils that disperse easily will form surface crust and/or clods on re-drying. If such soil is found deeper under the surface the soil will expand under wetting and this will force air-pockets out (decreasing the soilís porosity) and too little air can penetrate into lower regions for nitrogen fixation and root respiration.
Scoring dispersion:
0 No dispersion at 2 hours
1 Slight dispersion at 2 hours
2 Slight dispersion at 10 minutes and strong dispersion at 2 hours input Calcium
3 Strong dispersion at 10 minutes and full dispersion at 2 hours Calcium and AgSoap BR-Em00
4 Full dispersion at 10 minutes Calcium and AgSoap BR-Em00
Slake Testing (test for Organic Matter need)
To test for slaking of the soil, take a dry soil lump of about 1 - 2 cm (2/5 to 4/5 of one inch) and place into a 250 ml beaker that is filled with de-ionized water to a height of about 2.5 cm (1 inch). Distilled or rain water is OK, but de-ionized results in the most accurate test. It is important that the water be in the beaker before the soil lump is put in it and the test remains undisturbed from any kind of movement during the testing period.
The slake test is viewed at 5 minutes after the lump is put into the water.
Soils that slake into very small pieces will harden into one hard layer.
0 Lump intact
1 Lump shows signs of some collapse (mainly just at the edges)
2 Lump collapsed into large angular pieces
3 Lump collapsed into small (<2mm) pieces and forms a cone input OM
4 Lump collapsed into very small single grains OM and AgSoap BR-Em00
