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Optimise the solubility and availability of phosphorus in your soil

Phosphorus is an essential and irreplaceable chemical element for all living things. In today's agriculture it is of vital importance to maintain high yields in farming systems. It must be absorbed by plants from the soil, where it is found in a very low concentration in soluble form, typically at levels ranging from 5 to 30 mg kg-1. These low rates of the nutrient are due to the fact that soluble phosphorus reacts with ions such as calcium, iron or aluminium, which cause its precipitation or fixation, reducing its availability for plants (Rodríguez et al., 1999). Inorganic phosphates applied as chemical fertilisers are also immobilised in the soil and as a consequence are not soluble enough to be used by crops.   Fertilisation based on beneficial microorganisms, biofertilisers and biostimulants are a promising alternative to solve this problem. This technology is based on preparations of specific microorganisms that improve soil health and, therefore, plant development in multiple ways: facilitating access to nutrients, fixing atmospheric nitrogen, improving water absorption or acting as biological control agents. In addition, they fulfil the shortcomings of conventional fertilisers: they are biodegradable, renewable, non-toxic to auxiliary flora and fauna and do not generate waste. Microbial inoculants can improve the efficiency of plants to uptake phosphorus and nitrogen. And consequently reduce fertilisation costs and increase yields. Microorganisms carry out the processes of solubilisation, mineralisation and immobilisation. The main microbiological mechanism by which phosphate compounds are mobilised is the lowering of the pH of the medium by the release of organic acids (Alexander, 1980). This property is characteristic of gram-negative bacteria, including Pseudomonas (Fernández et al., 2005).   In nature, microorganisms co-exist in complex communities, which are known as the rhizosphere microbiome. Co-culture, also called mixed culture of different strains, has been shown to be effective in increasing the production of secondary metabolites (Ochi, 2017).  In in vitro tests, it is observed that the production of the solubilisation halo (yellow) after 72 hours is higher in the plates in cross co-culture versus individual growth of each of the strains Phosphate solubilisation test with the bacteria belonging to Bacnifos over time. The solubilisation of organic phosphorus is a process driven by enzymes, including phosphatases, which participate in the dephosphorylation of phosphodiester groups attached to organic matter, and phytases, which catalyse the hydrolysis process of phytic acid, sequentially releasing up to six free orthophosphate groups. Enzyme activity is frequently used as an indicator of soil microbial activity (Fernández et al., 2015). The selection of microorganisms with a high capacity to solubilise phosphorus and their testing under field conditions is a fundamental step to obtain a highly effective product.  In field trials on onion crops, with a 30% reduction in phosphate fertilisation, crop productivity increases of 7.6% and 22.9% with complete fertilisation, compared to the control with total fertilisation, were achieved. In terms of benefits for the farmer, taking into account the average productivity of onions obtained and the average price per kg of onion, it would mean about 300 є/ha (with reduction of phosphate fertiliser) and 900 є/ha with total fertilisation.


  • Rodríguez, H & R Fraga. (1999). Phosphate solubilizing bacteria and their role in plant growth promotion. Biotech. Adv. 17:319-339
  • Fernández, L. A., Zalba, P., Gómez, M. A., & Sagardoy, M. A. (2005). Bacterias solubilizadoras de fosfato inorgánico aisladas de suelos de la región sojera. Ciencia del suelo, 23(1), 31-37.
  • Alexander M. (1980). “Introducción a la Microbiología del Suelo”. AGT Editores, México pp. 234-362.
  • Ochi, K. (2017). Insights into microbial cryptic gene activation and strain improvement: principle, application and technical aspects. The Journal of antibiotics, 70(1), 25-40.

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