Rev. Bras. Ciênc. Solo.2025;49(spe1):e0240162.
Soil properties and pH of the extractors influence extraction and availability P in alkaline soils from the São Francisco Valley, Brazil
Patryk Ramon Graciano Rosa Wandersee 
, Maria Betânia Galvão dos Santos Freire , Fernando José Freire , Suellen Roberta Vasconcelos da Silva , Jailson Cavalcanti Cunha
12/nov/2025
DOI: 10.36783/18069657rbcs20240162
Resumo Gráfico
Destaques
Mehlich-1 extracted more P and had a lower correlation with the P content in the plant.
The pH of the extract of Melhich-1 was 7 times higher than the pH of the extractor.
AER was influenced by soil attributes reducing the prediction of available P.
Olsen was not influenced by soil attributes and available P was little effective.
Mehlich-3 showed high performance to assess P availability in alkaline soils.
ABSTRACT
Phosphorus (P) is one of the most used nutrients in agriculture due to its high degree of interaction with the soil. It is susceptible to calcium precipitation in poorly weathered and alkaline soils, such as those in the Brazilian Semi-Arid region. Mehlich-1 is the most used extractor to evaluate P availability in this region. However, there are controversies regarding the efficiency of Mehlich-1 and the anion exchange resin (AER) has been an alternative extractor to evaluate P availability. However, AER has not yet proven its efficiency in this region. Additionally, other extractors such as Mehlich-3 and Olsen need to be evaluated. This study aimed to correlate soil properties in an alkaline environment with the P extracted by Mehlich-1, AER, Mehlich-3 and Olsen extractors and assess the performance of these extractors in predicting P availability for Urochloa decumbens in representative soils of the sub-middle São Francisco Valley. An experiment was carried out with samples of six representative soils from productive areas of the sub-middle São Francisco Valley, Brazil. Soils were incubated with increasing P rates and after 30 days, soil samples were collected for P determination by the extractors Mehlich-1, AER, Mehlich-3, and Olsen, relating this extraction to soil properties. Soils were seeded with U. decumbens to determine biomass production and P accumulated in plant biomass, correlating this accumulation with the P extraction capacity of the extractors. Exchangeable Ca2+ content and soil pH influenced the P extraction rate more than clay and P-rem content. Mehlich-1 extractor overestimated available P. Anion exchange resin was also influenced by soil properties and showed low prediction of P availability. In contrast, Olsen extractor was not influenced by soil properties, but showed low prediction of available P. The pH of Mehlich-3 extracts was little altered during P extraction in the different soils, with the extraction of P influenced by the exchangeable Ca2+ contents and pH. However, Mehlich-3 showed high performance in predicting P availability in alkaline environments, suggesting that soil properties such as exchangeable Ca2+ and pH should be considered when P availability is evaluated in alkaline soils.
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