The availability of nutrientsin the

The availability of nutrientsin the bio-extract, for example, available forms ofnitrogen (NO3- and NH4+), available forms of phosphorous (H2PO- and HPO4 2-) and available forms of potassium (K+) could promote plant growth (Omsub, 2002). However, Pathanapibul (2003) reported that using only bio-extracts did not enhance plant growth, because the amount of
macronutrients and micronutrients in the bioextract was low and insufficient for plant growth. This finding was similar to the study by the Department of Agriculture (2004). Moreover, Khaliq et al. (2007) showed that using only EM (effective microorganisms, the production of which is similar to that of bio-extracts) for cotton production did not enhance the yield of cotton. In contrast with the study by Vetayasuporn (2004), EM promoted the growth of oyster mushrooms (Pleurotus ostreatus) by around two to four times, compared to that without EM treatment. Several groups of EM are able to degrade the complex organic compounds into simple molecules that can be utilized easily by the mushroom. The findings
indicated that the type of plants and the group of microorganisms in the bio-extract had an effect on the efficiency of the with regard to the enhancement of plant growth