Methods and compositions for estimating soil microbial load

A method of determining the microbial population of a sample of soil or compost, comprising

• (a) measuring a volume of the sample;
• (b) solubilizing microbes in the sample in a known volume of water comprising salt and/or detergent to form a microbial solution, separate from soil;
• (c) compensating for pigments in the microbial solution, if necessary, by adding a bleaching agent;
• (d) filtering the microbial solution through a filter allowing passage only of microorganisms and not soil to produce a filtrate comprising microorganisms approximately five microns in diameter or less;
• (e) measuring turbidity, reflectance or transmittance of the filtered microbial solution;
• and
• (f) determining the number of microbes in solution based upon the turbidity, reflectance or transmittance measurement by comparison to standard values of microbes based upon reference turbidity, reflectance or transmittance values.