In previous articles we have discussed Biological Fertilization and Biological Nitrogen Fertilization, this time Biological Phosphate Fertilization will be discussed.

It is convenient to emphasize that the concept of Biological Fertilization, referring to the utilization and improvement of natural processes or phenomena where living beings intervene, which serve to improve the availability and use of essential nutrients by plants, is very different from the concept of biofertilizers or organic fertilizers. These are any substance of animal or plant origin that is applied to the soil to improve its fertility, they have and generate life when they are incorporated into the soil, so they are capable of decomposing, transforming, mineralizing. Thus, they convert their nutrients to forms available to plants, improve the physical properties of soils such as structure and porosity, by increasing carbon levels improve soil life, and can buffer pH variations while increasing the capacity of cation exchange. In Biological Fertilization live microorganisms are used in the form of inoculants.

Diazotrophs, such as bacteria of the genera, are used in Biological Nitrogen Fertilization Bradyrhizobium y azospirillum, capable of fixing atmospheric nitrogen. In Biological Phosphate Fertilization there are two fundamental ways, one based on the use of microorganisms capable of solubilizing phosphates to make them available to plants; the other, the use of mycorrhizal fungi to associate with the roots of the plants and increase their exploratory capacity of soil, which allows the plant to achieve greater amounts of phosphorus in the soil solution.

-There is a group of soil microorganisms that have the ability to solubilize phosphates from the soil to make them available to plants. This is the case of fungi of the genera Aspergillus y Penicillium, which are mainly responsible for the solubilization of dicalcium phosphate; and bacteria of the genera Pseudomonas, Rhizobium y Bacillus, which can hydrolyze various phosphate compounds by producing acid phosphatase enzymes, to finally release the phosphorus that is insoluble in these compounds. These microorganisms, in addition, help to increase the efficiency of chemical fertilizers, and produce substances that stimulate plant growth or that have antagonistic effects on pathogenic microorganisms.

In the specific case of phosphorus, P-solubilizing bacteria (BSP) are generally present in soils, but their populations are not sufficient to compete with other microorganisms that abound at the level of the rhizosphere, therefore, to have a solubilization of P effective, it is necessary to perform inoculations with high populations or high concentrations of BSP. Based on this same principle, fertilizers with soluble P are produced, as in the case of PHS phosphoric fertilizer, produced by the fusion of phosphoric rock with elemental sulfur and inoculation with bacteria of the genus Thiobacillus. Bacteria oxidize sulfur, creating an acidic environment that solubilizes rock phosphate. In Venezuela, INIA and perhaps other organizations have evaluated BSP, among which the bacillus megatherium there. Phosphaticum.

-Mycorrhiza is defined as the symbiotic relationship between fungi and roots.

Mycorrhizal fungi play an important role in the use of soil P by many plant species, through a non-specific symbiosis that favors the absorption of this essential nutrient. The most important are Ectomycorrhizae that do not penetrate the cell wall of the roots, and Arbuscular Mycorrhizae that perform intracellular colonization and are identified as MA. Ectomycorrhizae are particularly important in timber species of great economic value, while AM ​​are present in all phyla including many gymnosperms and the vast majority of angiosperms.

MAs promote the absorption of water and nutrients by plants. This is very important in the case of P, since this is an element that is found in small concentrations in the soil solution, in addition to moving towards the roots of plants at a very low speed due to the diffusion phenomenon. An area with a lower concentration of P than in the rest of the soil solution is created around the roots, because the absorption speed by the plant is greater than the mobility of P towards the roots, which creates a flow by diffusion into the rhizosphere. MAs act as an extension of the root system, allowing plants to explore larger volumes of soil in their search for water and nutrients. Furthermore, MAs have been found to be more efficient at absorbing P in terms of absorption / root length than roots.

In conclusion, at times when greater efficiency is required in agricultural activity, when it is necessary to reduce production costs, and it is imperative to protect the environment by improving the life of the soil and its carbon sequestration to decrease the emission of greenhouse gases such as the CO₂, the use of Biological Fertilization whenever there is the possibility of applying it is an unavoidable obligation. We hope that the scientific and technological developments to come, will succeed in expanding the concept of Biological Fertilization to the greatest possible number of essential nutrients, beyond Nitrogen and Phosphorus, which will allow us to decrease the application of chemical fertilizers more and more, especially in the case of P when its sources are finite in nature.

Remember that: WITHOUT FERTILIZERS it is impossible to produce the amount of food we need to satisfy the population's requirements.