Evaluation of Mehlich‐III extractant to estimate the available P in Quebec soils

Abstract

The Mehlich-III method used for the determination of available P in 82 Quebec soils was compared to five other chemical methods (Bray-II, Bray-I, Mehlich-II, Mehlich-I and Olsen) and to two anion exchange resin techniques (F -and HCO -3 ) In general, very good correlations were found between Mehlich-III, Bray-II and Bray-I methods on acid soils (r=0.95** and 0.98**). The Mehlich-III-P content is somewhat the same as that determined by Bray-I and corresponds approximately to 80% of Bray-II-P. The Mehlich--III extractant was found to be more reliable than Bray-II and Bray-I on very acid spodosols having high P-sorption capacity. The Bray methods, with high NH 4 F concentration, extracted strongly fixed Al-P in these soils and may overestimate the available P. In some acid soils containing apatite and in calcareous soils, the Bray-II and Mehlich-I (double acid) easily dissolved these Ca-P compounds and gave exaggerated high P values. The Mehlich-III and the other methods were less vigourous for these compounds and were

Interlaboratory comparison of soil phosphorus extracted by various soil test methods

“…The solution extracts were all significantly correlated (r ¼ 0:77 to 0.94, P , 0.05). The weakest correlations between soil tests were found between Olsen P and Bray-1 P ðr ¼ 0:77Þ; and Olsen P and Mehlich-3 P ðr ¼ 0:84Þ: The strongest correlations between soil tests occurred between Mehlich-3 and Bray-1 P, as well as Olsen and Fe-strip P ðr ¼ 0:94Þ: Comparison of linear regressions reveals that Mehlich-3 and Bray-1 P were similar (approximately 1:1), which compares well with the regression equation reported by Tran et al (31). Average Olsen P and Fe-strip P values were also approximately 1:1 in average concentration.…”

Avaliação de métodos para estimativa da disponibilidade de fósforo para arroz em solos de Várzea do Rio Grande do Sul

“…Antes do cultivo do arroz irrigado, extraiu-se o P nas amostras de solo por diversos métodos: Mehlich-1 (Mehlich, 1953), Mehlich-2 (Mehlich, 1978), Mehlich-3 (Mehlich, 1984), Resina em lâminas (Gatiboni, 2003), Resina em esferas (Raij et al, 1987), Bray-1 (Bray & Kurtz, 1945), Bray-2 (Bray & Kurtz, 1945), Olsen (Tran et al, 1990), Morgan (Baker & Hall, 1967), Lactato de Ca (Steffens, 1994), Texas (Sharpley et al, 1987), Oxalato (Shahandeh et al, 1994), EDTA (Labhsetwar & Soltanpour, 1985), H 2 SO 4 (Catani & Gargantini, 1954) e NaOH (Chang & Jackson, 1957), cujos extratores e procedimentos utilizados na extração do P disponível estão resumidos no quadro 2. Outros detalhes operacionais encontramse em Ranno (2004).…”

Extratores de fósforo em solos da Amazônia tratados com fertilizantes fosfatados

“…Outros estudos têm evidenciado a eficiência do Mehlich-3 na extração de P do solo. Tran et al (1990) verificaram que o extrator foi mais confiável que o Bray-I e II, em solos ácidos com elevada capacidade de retenção de fósforo. Evans & McGuire (1990) constataram que esse extrator, juntamente com o Mehlich-1, apresentou as melhores correlações, não somente para P, mas também para K, Ca e Mg. Resultados semelhantes foram obtidos por Gascho et al (1990), tendo o método apresentado maior eficiência.…”

“…Segundo Jones (1990), esse extrator é considerado adequado para avaliar o P de solos que, atualmente, estão sendo analisados pelo extrator Mehlich-1. Dentre os métodos de extração ácida, o Mehlich-3 foi considerado como o mais econômico para análise de terra em laboratório, pela sua capacidade de extrair, simultaneamente, outros nutrientes (K, Ca, Mg, Na, B, Cu, Fe, Mn e Zn), além de P (Tran et al, 1990).…”