Potassium supplying capacity of soils from Minas Gerais-Brazil .

Nairam Felix de Barros,Arlindo Ferreira Faria Arlindo,Haroldo Nogueira de Paiva,Edson Marcio Mattiello Mattiello,Vitor Hugo Alvarez V.,Julio Cesar Lima Neves

doi:10.3232/sjss.2012.v2.n1.02

Abstract

Potassium is present in distinct forms in the soil. The K forms in the soil are characterized by reversible exchanges between compartments and they have different characteristics in regards to availability for plant uptake. The soil's capacity to supply or restrict K to plants is different for each soil and it determines the sustainability of agricultural production and fertilization management. Thus, the goal of this study was to evaluate the K supplying capacity of soils of different mineralogies from Minas Gerais (Brazil), under successive corn cultivation. A greenhouse experiment was carried out in factorial 7 x 6 (seven soils and six rates of K), in a randomized complete block design, with four replications. The corn plants were cultivated during 45 days for seven successive crop cycles in pots. The potassium availability in the soil was evaluated at the beginning and at the end of each crop cycle using Mehlich-1 and Mehlich-3 extractors. All treatments showed significant decreases in soil K content, which affected corn dry matter accumulation. The reserve of K was highest in Ultisols followed by Inceptisols and Oxisols. Contribution of non-exchangeable potassium to the plant nutrition was observed. The K availability in soil measured by Mehlich-1 represented 40% of K uptake by plants, and 61% of K uptake when Mehlich-3 was used.

Highlights

Potassium is present in distinct forms in the soil
The soil’s capacity to supply or restrict K to plants is different for each soil and it determines the sustainability of agricultural production and fertilization management
The corn plants were cultivated during 45 days for seven successive crop cycles in pots

Summary

Introdução

O K está presente no solo nas formas estrutural, não trocável, trocável e em solução, diferindo na acessibilidade para as plantas e com reversibilidade entre essas formas (Syers 2003). Esses ensaios permitem avaliar a contribuição das diferentes formas de K na nutrição das plantas e a capacidade de suprimento de K pelo solo ao longo dos cultivos. Lana e Neves (1994) avaliaram a exaustão do K do solo por meio de cultivos sucessivos com eucalipto, em seis solos, e observaram maior produção de matéria seca e maior absorção de K nos primeiros cultivos, refletindo a contribuição da reserva imediata de K para as plantas, representada pelo K trocável. Como o K não trocável pode ser uma fonte disponível para as plantas ao longo de seu ciclo de vida, verifica-se a necessidade de conhecer melhor a cinética de liberação desta forma de K para a solução do solo, que depende principalmente de fatores relacionados com a mineralogia do solo e a sua proporção em cada fração granulométrica (Bortoluzzi et al 2005).

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