A Comparison of Microbial Technologies on Growth and Phytoremediation Potentials of Syzygium accuminatissimum (Blume) DC. in Heavy Metal-Contaminated Environment

Abstract

This study aimed to investigate the potentials of the copper mine-derived inoculants, NMYC and NNFB, containing indigenous arbuscular mycorrhizal fungi (AMF) and nitrogen-fixing bacteria (NFB), respectively, as compared to the commercial biofertilizers’, MYKORICH^® and MYKOCAP^®, in improving the growth of Syzygium accuminatissimum (Blume) DC.  used in phytoremediation of gold (Au)-mined area in Placer, Surigao del Norte for a span of 19 months. The soil microbial community and mineralogical status were also determined. Treatments did not significantly vary from each other in height and diameter increments, although the commercial inoculants significantly differed from the untreated control. Specifically, MYKORICH^®-treated plants were significantly taller than the untreated ones, while MYKOCAP^®-treated plants had significantly bigger stem diameters than the untreated ones at 19 MAF. Except for these, the new inoculants were comparable to MYKOCAP^® in effects on height, and to MYKORICH^® in diameter increment. Here, the effectiveness of the indigenous Cu AMF isolates in bioremediation was emphasized based on the improvement in soil nitrogen content, pH level, AMF density and NFB community, OM, OC, and available P, and a decrease in Pd concentration. When combined to indigenous NFB, NMYC had the highest Cu reduction capacity. These effects are further corroborated by the strong positive correlations between and among the three parameters such as N, OC, and OM and a strong negative correlation between soil pH and AMF density. The effectiveness of indigenous fungal isolate alone or in combination with the indigenous NFB isolate was comparable or higher than the commercial inoculants. The new inoculants NMYC alone or its combination with NNFB can be a potential biofertilizer for bioremediation; however, further cross validation is necessary to establish its effects to different forest tree species and HM contaminated environments.