Organic Bloom – Adsorption of phosphorus in soil*

Phosphorus (P) is the utmost importance element for plant metabolism, especially for its establishment and development , as when applied  adequate amounts, benefits the process of germination, root growth and its greatest yield potential.

This element is characterized by being little mobile and easy retention, easily undergoes losses due to percolation (underground water movement through the soil). Erosion can be the main responsible for phosphorus losses when there is loss of organic matter and colloidal particles with this nutrient.

Its availability in the soil depends on the physical and chemical reactions such as adsorption, desorption and precipitation, in addition to the biological processes, such as immobilization of inorganic P and organic P mineralization. Thus, the phosphorus is found in the solid phase in two forms: organic and inorganic, and in the liquid phase in inorganic forms in the soil solution. The P contained in the soil parent material is available in the form of minerals, predominantly phosphates, through the weathering this element is released to the solution in small quantities.

Total P to most soils may be relatively large, however geochemical and biological processes can transform the natural phosphates in stable forms, fixed, combined with other elements such as calcium, iron or aluminum forming compounds not assimilated by plants (P-labile). In addition, in the soil P can be immobilized  (when available in organic form can not be assimilated by plants, making it fit for the plant by the mineralization of organic matter) or adsorbed (characterize the manner in which the fraction of phosphorus attached to the colloid  complex of the soil is made available through trade with the roots) and assimilable (part which is diluted in the soil solution being easily absorbed by plants).

Phosphorus adsorption, a generic term for any process that results in the retention of the element, is one of the most studied phenomenon due to their complexity. Some soil characteristics, such as clays  mineralogy, content of amorphous non-crystalline colloids and organic matter content influence the adsorption of phosphorus. In soils classified as Latosols where there is a predominance of kaolinite and iron oxides (Fe) and aluminum (Al), the adsorption process decreases the amount of inorganic P in the labile fraction, due to the high binding energy between the phosphate anion and functional groups of mineral surface.

Another factor that aggravates the deficiencies of this nutrient to the plant is theaccelerated mineralization of organic P by inadequate soil management, because the element passes initially from labile forms to others less and less available. It is believed that the retention of P in organic forms leads to a more sustainable systems because there is retardation of P adsorption process with high energy.

In order to reduce the effects of this phenomenon in the soil, the adoption of soil management systems that provide the increase of organic matter (OM), higher pH and higher microbial activity, they become fundamental tools. This is because, carboxylic and phenolic functional groups present in the OM are responsible for blocking the positively charged sites of Fe and Al oxides, reducing the adsorption of P. Since the increase in the soil pH by liming, allows the concentration and activity of OH- ions insolution and thus there is a Fe and Al precipitation, reducing precipitation phosphorus-Al and phosphorus-Fe.

In this environment, the use of no-tillage, crop rotation and appropriate fertilizers are factors that must be taken into account to ensure good soil management minimizing the effects of phosphorus adsorption.

Fertilizer Organic Bloom, organic source of phosphorus and amino acids, is an alternative to be used by crop producers to supplement the basic fertilization and provide phosphorus to the plant. Due to its formulation, it is a chelated product that neutralizes the action of other elements which may be harmful to plants, and to prevent it from absorbing the nutrients necessary for their full development.

 

* Fernanda Mugnol- Eng Agronomist -. CREA RS 178798. Post graduate in MBE Expertise, Audit and Environmental Management

References :

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Martinazzo, Rosane et al. Fósforo microbiano do solo sob sistema plantio direto em resposta à adição de fosfato solúvel. Rev. Bras. Ciênc. Solo, Jun 2007, vol.31, no.3, p.563-570.

Pereira, Marcos Gervasio et al. Carbono, matéria orgânica leve e fósforo remanescente em diferentes sistemas de manejo do solo. Pesq. agropec. bras., Maio 2010, vol.45, no.5, p.508-514.

Prates, Fabiano Barbosa de Souza et al. Crescimento de mudas de maracujázeiro-amarelo em resposta à adubação com superfosfato simples e pó de rocha. Rev. Ceres, Abr 2010, vol.57, no.2, p.239-246.

Souza, Renato Ferreira de et al. Calagem e adubação orgânica: influência na adsorção de fósforo em solos.Rev. Bras. Ciênc. Solo, Dez 2006, vol.30, no.6, p.975-983.