Comparison of methods for extracting available phosphorus from soils of the semi-arid

• Published in: Ciência agronômica Vol. 52; no. 4
• Main Authors: Oliveira do N. M, Maria Deuzilene, Oliveira, Fábio Henrique Tavares de, Preston, Welka, Paiva, Maria Regilene de Freitas Costa, Góis, Helena Maria de Morais Neta
• Format: Journal Article
• Language: English
• Published: Universidade Federal do Ceará 01-01-2021
• Subjects: AGRONOMY; Alkaline soils; Ion-exchange resin; Mehlich-1; Olsen; Mehlich-1; Olsen; Resina trocadora de íons; Solos alcalinos; Alkaline soils; Ion-exchange resin
• ISSN: 1806-6690; 1806-6690
• DOI: 10.5935/1806-6690.20210062

ABSTRACT Mehlich-1 is the most used method in Brazil for extracting available phosphorus (P) from the soil. Given the heterogeneity of soils in the semi-arid region of the Northeast, and the need for an analytical protocol for P extraction, the Mehlich-1, Olsen and ion-exchange resin methods were compared in samples of ten representative soils taken from the semi-arid region between the valley of the River Piranhas-Açu (Rio Grande do Norte) and the valley of the River Jaguaribe (Ceará), where the soil pH ranges from 4.1 to 8.0. The soil samples received four doses of P based on the phosphate buffering capacity (PBC) of the soils, and were incubated for 30 days. The treatments were divided into randomised blocks, in a 10×4 factorial arrangement of ten soils and four doses of phosphorus, with three replications. Each experimental unit comprised one plastic pot containing 3.0 dm3 of soil, where two maize plants were grown for 31 days in a greenhouse. The P extracted by each method was correlated with the P accumulated in the aerial part of the plants. The mixed-resin and Olsen methods showed the best correlation with the P accumulated in the plants, irrespective of the pH or PBC of the soil. Neutralisation of the acidity of Mehlich-1 was significant in alkaline soils with high levels of CaCO3 equivalent. Mehlich-1 was suitable for strongly acidic soils with a low PBC, however, the use of this extractor in pH neutral to alkaline soils with a high Ca2+ content can overestimate P availability when the soils are rich in P-Ca, or underestimate the availability in soils rich in CaCO3.