Effect of different organic residues on some vermicompost properties and nutrient trend during vermicomposting process

This study was conducted in order to investigate the changes of nutrient status during vermicomposting process from various organic residues. Organic materials included cow manure wheat bran (CB), cow manure wheat straw (CS), cow manure sycamore and maple litter (CL), cow manure apple and grape pruning waste (CP), cow manure lemon balm extract wastes (CE) along with cow manure as control (C). These organic residues were treated in the presence of Eisenia fetida. Some properties of vermicompost and changes in nutrient contents were evaluated at 0, 60, 120 and 180 days. The results showed that EC and pH significantly increased over time in all examined organic wastes and ranged from 1.9 to 3.8 dSm-1 for EC and from 6.5 to 7.4 for pH. Cation exchange capacity (CEC) also increased noticeably, so that the highest CEC amount was observed at 180 days in CS treatment by 364 cmol()kg-1. Furthermore, P and K contents in decomposed organic wastes increased significantly and the highest amounts were obtained in CP and CS treatments by 1.01 and 2.31 %, respectively. The same uptrend happened for N content in CP, CE and CL treatments by 2.51, 1.97 and 1.91 fold compared to initial amounts. On the other hand, Organic carbon significantly decreased during decomposition and the highest decrement in organic carbon content was observed in CE and C treatments by 0.54 and 0.53 fold compared to initial values. C/N ratio in all examined treatments significantly decreased where the highest C/N ratio and the lowest decrease obtained in CP and C treatments by 0.22 and 0.47 fold compared to initial values. NO3- and NH4 significantly increased during vermicomposting process as nitrate content was more than ammonium content in all treatments. Increasing the nutrients amount due to organic matter mineralization, is the effective factor in maturity level of vermicompost.