Soil extract agar

Preparation of soil extract

• The following make 1 L of soil extract, this can be adjusted down if 1 L is too much.

Choosing soil

• Choose soil the same or similar to soil you are sampling from.
• The soil should not contain too much humus or clay
• Avoid soil treated with fertilizers, herbicides or fungicides

Making soil extract

• place ~400 g of soil into a 2 L flask
• Add add 700 mL of distilled H2O
• Shake vigorously
• Autoclave for 1 h at 121 °C and let cool down
• After 24 h autoclave for a second time (for 1 h at 121 °C)
• Remove bigger particles by filtering through cheesecloth
• Filter through Whatman filter 595 (1/2, 320 mm) to remove residual particles
• Filter sterilize
• Store at 4°C – 10°C