Phosphorus dynamics and sustainable agriculture: The role of microbial solubilization and innovations in nutrient management

Abstract

Phosphorus (P) is an essential element for plant growth, playing a crucial role in various metabolic processes. Despite its importance, phosphorus availability in soils is often restricted due to its tendency to form insoluble complexes, limiting plant uptake. The increasing demand for phosphorus in agriculture, combined with limited global reserves of phosphate rock, has created challenges for sustainable plant production. Additionally, the overuse of chemical phosphorus fertilizers has resulted in environmental degradation, such as eutrophication of water bodies. Increasing agronomic phosphorus (P) efficiency is crucial because of population growth and increased food demand. Hence, microorganisms involved in the P cycle are a promising biotechnological strategy that has gained global interest in recent decades. Microorganisms' solubilization of phosphate rock (PR) is an environmentally sustainable alternative to chemical processing for producing phosphate fertilizers. Phosphorus-solubilizing microorganisms (PSMs), including bacteria and fungi, and their enzymatic processes offer an eco-friendly and sustainable alternative to chemical inputs by converting insoluble phosphorus into forms readily available for plant uptake. Integrating PSMs into agricultural systems presents a promising strategy to reduce dependence on chemical fertilizers, enhance soil health, and contribute to the transition toward more sustainable and resilient agricultural practices. It can be an alternative that reduces the loss of phosphorus in the environment, especially the eutrophication of aquatic systems. This paper explores the challenges of phosphorus availability in agriculture and the potential of microbial phosphorus solubilization as a sustainable alternative to conventional practices.

Keywords: Phosphate rock; Phosphorus; Phosphorus-solubilizing microorganisms; Sustainable agriculture.

Graphical abstract

Fig 1

Periodic table of the elements that occur in apatite minerals and Diagrammatic representation of a complete ternary solid-solution series. a) The elements present in apatite supergroup minerals in the range of ppm to several tenths’ percent of total weight. The relevant elements are shown in red. This figure was prepared by Hughes and Rakovan (2015) based on the data from Pan and Fleet (2002). b) Diagrammatic representation of a complete ternary solid-solution series. A, B, and C represent the three compositional fields that merit a mineral name. Considering apatite as an example, the three vertices (A, B, and C) representing fluorapatite, hydroxyapatite, and chlorapatite, respectively. Then by the 50 % rule, in the OH-F system, the components of Ca₁₀(PO₄)₆(OH)₂ to Ca₁₀(PO₄)₆(OH, F) are called hydroxyapatite (Kono et al. 2022).

Fig. 2

Development process of microbial inoculants for the use of phosphate rock as a sustainable agricultural production strategy. The red arrows indicate the steps to follow; however, they are only representative since the methodologies used vary depending on the available resources and the advancement of microbiological characterization techniques. The solubility of phosphorus carried out by soil microbes may be mediated by the release of organic acids, production of enzymes, or acidification mechanisms (release of protons) that facilitate the absorption of phosphate available (HPO₄^2–, PO₄^3-, H₂PO^4–) for plants (Raymond et al., 2021). In this work, we also propose evaluating and measuring phosphorus solubility based on microbial activity and considering the biosafety of the inoculant.

Fig. 3

Technique for the microbial solubilization activity of phosphoric rock. The red arrows describe the research process implemented in our laboratory to develop a methodology for evaluating, characterizing, and measuring microbial solubilization activity. In this example, the phosphorus source used is commercial phosphate rock; however, other sources of phosphorus can be implemented. Phosphorus includes dicalcium, tricalcium phosphate, magnesium phosphate, apatite, and other sources of insoluble phosphorus. Also, organic and inorganic acids are used to quantify the soluble phosphorus of different arrays.