Humic acids were extracted from vermicomposts and a range of doses added to
tomato seedlings that were provided with all needed nutrients. Greenhouse experimer.ts
with some humate doses produced very significant increases in plant growth in
greenhouse experiment (Figure 5). The humic acids were extracted from pig manurebased
vermicomposts, using the classic alkali/acid fractionation procedure (Valdrighi et
al. 1996). The dry yield of humates was 4 gm kg-I of vermicomposts. The incorporation
of 150,200,250 and 500 mglkg of humates from pig manure vermicompost into MetroMix
360 increased the heights and the leaf areas of tomato seedlings grown in these
mixtures significantly, compared to those grown in the Metro-Mix 360 controls with no
lumates added. The greatest plant heights