Preparation and utilization of phosphate biofertilizers using agricultural waste

Abstract

In this study, Aspergillus niger 1107 was isolated and identified as an efficient phosphate-solubilizing fungus (PSF). This strain generated 689 mg soluble P L−1 NBRIP medium after 10 d of culture. To produce an affordable biofertilizer using A. niger 1107, the potential of widely available carrier materials for growth and maintenance of this strain were evaluated. The effects of sterilization procedures (autoclaving and gamma-ray irradiation) on the suitability of these carriers to maintain growth of the fungus were also investigated. The carrier materials were peat, corn cobs with 20% (w/w) perlite (CCP), wheat husks with 20% (w/w) perlite (WHP), and composted cattle manure with 20% (w/w) perlite (CCMP). In the first 5–6 mon of storage, the carriers sterilized by gamma-ray irradiation maintained higher inoculum loads than those in carriers sterilized by autoclaving. However, this effect was not detectable after 7 mon of storage. For the P-biofertilizer on WHP, more than 2.0×107 viable spores of A. niger g−1 inoculant survived after 7 mon of storage. When this biofertilizer was applied to Chinese cabbage in a pot experiment, there were 5.6×106 spores of A. niger g−1 soil before plant harvesting. In the pot experiment, Chinese cabbage plants grown in soil treated with peat- and WHP-based P-biofertilizers showed significantly greater growth (P<0.05) than that of plants grown in soil treated with free-cell biofertilizer or the CCMP-based biofertilizer. Also, the peat- and WHP-based P-biofertilizers increased the available P content in soil.

Keywords

• biofertilizer carrier
• sterilization method
• phosphate biofertilizer
• P-solubilizing fungi
• Aspergillus niger