Phosphorus in alkaline soils of the semiarid region, Brazil: inorganic fractions, capacity factor, and availability

Abstract

The study was designed to quantify the contents of Pi fractions and correlate them with the P capacity factor of soils in the Brazilian semiarid region. We also evaluated the effect of soil P doses contact time and P availability for maize plants in alkaline soils of the Brazilian semiarid region. Soil samples were collected between the Piranhas-Açu (RN) and Jaguaribe (CE) rivers valleys. The maximum phosphate sorption capacity was highly correlated with the values of remaining P, indicating that it can be used as a measure to estimate the P capacity factor of these soils. Maximum P sorption capacity correlated with Fe₂O₃ and Ca²⁺ contents and pH values. These results demonstrate that P sorption is explained by P adsorption on the surface of iron oxides and by its precipitation with Ca²⁺ in alkaline soils. The contact time increases promote plant P contents decreased substantially in the first 30 to 60 days after fertilization and decreased until 120 days of incubation but then tended to stabilize at the longest soil P contact times.

Novelty statement

The clay content and P-remnant estimate the P capacity factor in alkaline soils.

In alkaline soils, there is a predominance of P–Ca and P–Fe.

The availability of P stabilizes after 120 days.

The largest corn biomass occurs between the P doses of 256–288 mg dm⁻³.

Keywords:

• Calcareous soils
• contact times
• phosphate fertilization
• phosphorus phytoextraction
• sorption
• Zea mays L