Manganese toxicity in Portuguese Cambisols derived from granitic rocks: causes, limitations of soil analyses and possible solutions

Abstract

A B S T R A C TCambisols are the major Reference Soil Group in Portugal. The yield of annual crops in these soils is generally poor, and the situation is aggravated in wet winters. In the south of Portugal, manganese toxicity has been identified as the major cause of poor growth and leaching as the main reason for the negative effect of rainfall observed in Cambisols developed on granitic formations. Manganese toxicity also appears to be present in the Cambisols in other regions of Portugal. Manganese toxicity is cross-related to the magnesium concentration, either in the soil solution or in plant shoots. Therefore, soil amendment using dolomitic limestone is needed to overcome the problem. Current soil test methods are unable to predict the level of Mn toxicity. However, new approach using the extraction of soil solution is proposed, although further work is needed to fully implement the method.Keywords: leaching, magnesium, Mg/Mn ratio, Soil, soil amendment R E S U M OOs Cambissolos são o Grupo de Referência de Solos mais representativo em Portugal. As produções das culturas anuais são geralmente baixas e a situação agrava-se em anos de Inverno húmido. A toxicidade de manganês foi identificada como a principal causa das produções baixas e a lixiviação o principal efeito negativo dos Invernos húmidos nos Cambissolos derivados de granito no Sul de Portugal. A toxicidade de Mn está relacionada com um desequilíbrio com o magnésio, quer na solução do solo quer na concentração dos dois iões na parte aérea da planta. A solução do problema exige, assim, a aplicação de calcário dolomítico. Os actuais métodos de análise de solo não parecem capazes de prever a ocorrência da toxicidade de manganês. Uma nova abordagem utilizando a extracção da solução do solo é proposta. No entanto, a utilização desta abordagem exige investigação suplementar. A toxicidade de Mn pode não ser restrita aos Cambissolos do sul do país.Palavras-chave: lixiviação, magnésio, razão Mg/Mn, Solo, correcção do solo

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“…strain LMS-1 [ 79 ], as previously described [ 80 ]. Dolomitic limestone was applied at a rate of 1000 mg·kg −1 of soil according to a previous study [ 81 ]. To test the hypothesis that soil influences the endophytic bacterial communities, three soil samples from Alcaçer do Sal region, Portugal, were collected and their pH and electrical conductivity values were determined ( Figure 7 ).…”

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Evaluation of Near Infrared Spectroscopy (NIRS) for Estimating Soil Organic Matter and Phosphorus in Mediterranean Montado Ecosystem

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