Fixação do potássio nos solos portugueses
Data
2018
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Em Portugal, desde os anos 30 do século XX, os resultados da experimentação relativa à adubação potássica têm amiúde causado perplexidade entre os investigadores. Nos casos em que se esperariam respostas evidentes ao K, devido às suas baixas concentrações no solo, elas ou não se verificaram, ou tardaram a surgir, sobretudo no Sul do país. Neste trabalho de revisão, faz-se uma retrospectiva da experimentação realizada, na qual parece evidente a ineficácia da adubação potássica. Inventariaram-se as unidades-solo onde foram detectados indícios da fixação do K através de ensaios experimentais, bem como as unidades-solo submetidas a ensaios laboratoriais em que foi evidente a sua elevada capacidade de fixação do K. Relativamente à fixação, além da identificação dos solos fixadores de K, discutiram-se ainda os factores propícios à fixação deste nutriente, dos quais se salienta a composição mineralógica dos solos nas fracções argila, limo e areia fina. Por fim, com base nos estudos já realizados apontam-se estratégias a seguir na adubação potássica.
In Portugal, since the 1930s, the results of experimentation on potassium fertilization have frequently caused perplexity among researchers. In such cases, where clear responses to K were expected due to low K concentrations in the soils, they did not occur or were very slow in manifesting themselves, particularly in the south of the country. In this review paper a retrospective of the existing experimentation was carried out where the inefficacy of K fertilization was evident. In addition, an inventory of soil types was made where evidence of K fixation had been most often detected, either through experimental trials or through laboratory tests. The laboratory data refer to the determination of soil K fixation capacity. With regard to K fixation, in addition to the identification of the K-fixing soils, the propitious factors for fixation of this nutrient are discussed, highlighting the mineralogical composition of soils in the clay, silt and fine sand fractions. Finally, based on the studies already carried out, some strategies to be followed in potassium fertilization were proposed.
In Portugal, since the 1930s, the results of experimentation on potassium fertilization have frequently caused perplexity among researchers. In such cases, where clear responses to K were expected due to low K concentrations in the soils, they did not occur or were very slow in manifesting themselves, particularly in the south of the country. In this review paper a retrospective of the existing experimentation was carried out where the inefficacy of K fertilization was evident. In addition, an inventory of soil types was made where evidence of K fixation had been most often detected, either through experimental trials or through laboratory tests. The laboratory data refer to the determination of soil K fixation capacity. With regard to K fixation, in addition to the identification of the K-fixing soils, the propitious factors for fixation of this nutrient are discussed, highlighting the mineralogical composition of soils in the clay, silt and fine sand fractions. Finally, based on the studies already carried out, some strategies to be followed in potassium fertilization were proposed.
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filossilicatos , mineralogia das fracções do solo , potássio extraível , potássio de troca , capacidade de fixação do potássio