The Effects of Different Vermicomposts on the Growth and Chemical Composition of the Pistachio Seedlings

Samples of different solid organic wastes (SOW) including cow manure (CM), pistachio wastes (PW), cotton residues (CR) and date wastes (DW) were collected from different regions of Iran and converted to various vermicomposts. Each vermicompost had an iron-enriched counterpart produced by gradual addition of ferrous sulphate to organic wastes during the vermicomposting. Samples of a loamy soil were mixed with various proportions of prepared vermicomposts and pistachio seedlings were grown in 3 kg pots filled with them, for six months. During the period of experiment, some growth indices such as seed germination percentage, leaf area index, leaf chlorophyll content, leaves number, stem diameter and photosynthesis rate were measured for each treatment. After growing period, shoot and root dry weights and also macro and micro elements were measured. After vermicomposting, there was a substantial decrease in organic carbon content, total K and electrical conductivity of organic wastes. However, the contents of ash, N, P, Ca, Mg and some micronutrients including Fe, Mn, Zn and Cu increased in vermicomposted organic wastes. The pH of organic wastes shifted toward neutrality and their bulk densities were changed. There was a significant increase in seed germination, leaf area index, shoot dry weight and stem diameter in pots treated with 10% pistachio and cow manure vermicomposts in comparison with control and other treatments. Due to fungi growth and seed infection, germination did not occur in pots treated with date vermicompost so this organic amendment was not a suitable component for potting media. Vermicomposts enriched with ferrous sulphate increased chlorophyll and Fe contents of leaves.