Peat moss has been a standard carrier of inoculum for experimentation and in agriculture. Peat moss is, however, a non-renewable resource. Alternatively, biochar could serve as an inoculum carrier. Here, we tested the effect of biocharbased seed coatings as a carrier for the phosphoroussolubilizing Pseudomonas libanensis inoculum, on corn growth after soluble and insoluble P addition. The survival of P. libanensis was determined based on the measure of colony-forming units from samples of four inoculated guar gum-based biochar coatings and was compared to peat. Storage experiments were performed on inoculated biochars for 22 weeks at 25°C and on coated corn seeds for 16 weeks at 4°C. Seed coatings were prepared with inoculated and uninoculated biochars (100 seeds treatment −1 ), and effects of these treatments are reported on indices of seed germination after 7 days. A greenhouse experiment investigated the effects of the inoculated and uninoculated biochar seed coating on corn plants. The parameters measured from the greenhouse-grown corn plants were germination, fresh weight, dry weight, height, root length, basal stem diameter, leaf area, chlorophyll content, and tissue phosphorous. Our results show that corn plants grown from seeds coated with a biochar from hardwood feedstock are 2 to 10 g heavier than controls and that controls are 4 to 26 % shorter than the plants grown from biocharcoated seeds, where soluble phosphorous is applied.Moreover, corn seeds that were coated with a biochar produced from softwood feedstock germinated more quickly, based on the speed of germination index. Overall, we show that a biochar-based seed coating can benefit sustainable agriculture by carrying P. libanensis and enhancing the growth of corn, but according to parametric statistical tests, it does so without increasing the phosphorous content of the plants.

Most rhizobial inoculants that stimulate legume yield are applied with carriers that enhance root contact. The physicochemical properties of biochar are suitable for microbial growth, and it could be an alternative to peat, which comes from decreasing reserves but is the commonest solid inoculant carrier. The aim of the current research was to evaluate biochars as carriers of bradyrhizobia in solid inoculant and as coatings for seeds. Biochars and peat were inoculated with Bradyrhizobium japonicum strain 532C and storage time was assessed. A seed coating system was developed using biochar, bacteria liquid culture, water, and guar gum. The viability of bacteria in the coating and in solid biochar was evaluated at 4˚C and 21˚C. Two biochars were selected for a germination assay. Finally, greenhouse experimentation investigated the effect of biochar inoculant and seed coating on soybean growth and nutrient uptake. The storage time experiment showed that not all biochars equally sustain bacteria survival over time. The germination assay demonstrated that biochar seed coating had no effect on soybean germination. Greenhouse experimentation indicated that the effect of Pyrovac biochar on soybean growth characteristics and nutrient uptake depended on the fertilizer. The main finding was that biochar solid inoculant positively affected plant growth metrics, root characteristics, and the chemical composition of plants supplied with N-free nutrient solution.

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A. (2020). Role of in situ natural organic matter in mobilizing as during microbial reduction of FeIII-mineral-bearing aquifer sediments from Hanoi (Vietnam). Environmental Science and Technology.

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