Phosphate-Solubilizing Fungi and Alkaline Phosphatase Trigger the P Solubilization During the Co-composting of Sorghum Straw Residues With Burkina Faso Phosphate Rock

Abstract

Phosphate rocks (PR), the primary source of phosphorus (P), are often co-composted with organic materials to enhance P availability. However, the mechanisms of P solubilization in PR-enriched composts are not well elucidated. This study investigated such mechanisms by monitoring the changes in P fractions during composting and by determining the relationships between the physicochemical and biological parameters. Sorghum straw residues were composted alone (Comp), or with 10% PR (P-Comp), or with 10% PR and 10% rhizosphere soil (P-Comp-Soil), and samples were collected at 45, 60, and 180 days for analysis. The labile-P composed of H 2 O-and NaHCO 3extractable inorganic P (Pi) and organic P (Po), the moderately labile-P extracted by NaOH (Pi + Po), and the unavailable P formed of the HCl-P and residual-P, increased with the progress of the composting. At 180 days, P-Comp-Soil contained the highest amount of labile-P. There were strong and positive correlations between labile-P and the abundance of total fungi, phosphate-solubilizing fungi (PSF), alkaline phosphatase phoD, phosphonatase phnX, acid phosphatase aphA. Although total fungi were much fewer than total bacteria, the PSF mainly triggered the mineral P solubilization. The alkaline phosphatase phoD was the main enzyme leading the organic P mineralization, while the contribution of phosphonatase phnX, acid phosphatase aphA, and siderophore entA to the organic P solubilization was minor. Besides, the bacterial specific-transporter (pstS) gene increased with the increase of labile-P, allowing for immobilization of little fractions of P in microbial cells. This study highlighted the significant role of PSF and alkaline phosphatase in the P solubilization of PR-enriched composts. Furthermore, it showed the benefit of supplementing the PRenriched composts with rhizosphere soil, a niche of ecologically important source of beneficial microbes.

Sorghum Agronomic Performance and Soil Chemical and Microbiological Properties as Influenced by Burkina Faso Phosphate Rock-Enriched Composts

“…Therefore, the increased exchangeable cations in soils amended with P-Comp-Soil, particularly calcium and magnesium (data not shown), could be derived from the enhanced microbial-mediated phosphate solubilization during composting, concomitantly releasing more cations in the compost product and in soil. Sarr et al (2020) found in this type of compost a higher number of phosphate-solubilizing fungi and phosphatase-releasing microbial genes. Phosphate-solubilizing bacteria and fungi (Liu et Penicillium pinophilum has been shown to increase the phosphate availability in soil and the biomass yields of sorghum (Steiner et al 2016).…”

“…Pcompost-soil (P-Comp-Soil) was made by adding BPR and sorghum rhizosphere soil to the sorghum straw residues during the fabrication process. Sarr et al (2020) reported that the P-Comp-Soil contained 13% higher labile-P than the P-Comp. In the present study, the application rate of the organic materials (SS, Comp, P-Comp, P-Comp-Soil) was 1.34 t ha -1 .…”

“…Microbial genes associated with phosphate solubilization/mineralization encode phosphoesterases, phytases, phosphonatases, phosphatases, phosphate transporters, regulators (Liu et al 2018), siderophores (Ghosh et al 2015), and exopolysaccharides (Yi et al 2008). Therefore, the diversity and abundance of these genes are essential for phosphate solubilization, as reported by Sarr et al (2020).…”

Sorghum-Phosphate Solubilizers Interactions: Crop Nutrition, Biotic Stress Alleviation, and Yield Optimization

“…The PSM controls the phytopathogens attack by synthesizing pivotal molecules like siderophores ( Sarr et al, 2020 ), antibiotics ( Raaijmakers and Mazzola, 2012 ), lytic enzymes ( Herrera-Quiterio et al, 2020 ), cyanogenic compounds ( Munir et al, 2019 ), and through induction of systemic resistance (ISR; Audenaert et al, 2002 ). Due to this, the soil PSM improves the growth and grain yield of sorghum by suppressing the damaging impact of biotic stresses.…”

Efficiency of the Hydroponic System as an Approach to Confirm the Solubilization of CaHPO4 by Microbial Strains Using Glycine max as a Model

“…Currently, the use of phosphate-solubilizing microbes (PSMs) has been shown as a promising method since they play a key role in P dynamics in soil and the subsequent availability of this element to plants (Islam and Hossain, 2012;Kafle et al, 2019). PSMs fractionate insoluble P forms into soluble forms through various biological mechanisms, including the production of organic acids and extracellular enzymes, which convert insoluble forms of P into forms available for plant absorption (Hanif et al, 2015;Li et al, 2015;Baliah et al, 2016;Gurikar et al, 2016;Doilom et al, 2020;Sarr et al, 2020;Zúñiga-Silgado et al, 2020). The organic acids produced include glycolic, 2-ketogluconic, acetic, citric, propionic, succinic, tartaric, formic, fumaric, lactic, malic, butyric, gluconic, valeric, oxalic, and citric acids (Hwangbo et al, 2003;Chen et al, 2006;Patel et al, 2008;Scervino et al, 2010;Zhu et al, 2012;Jog et al, 2014;Mehta et al, 2015;Yadav et al, 2015).…”