Study and dynamics of potassium in agricultural soils of Uruguay

Doctoral thesis abstract

Resumo

Exchangeable potassium (K) and K in solution are considered “available” forms of this nutrient for plants. These forms can be estimated through chemical analysis of the soil, which are considered one of the best tools for proper management of soil nutrients. These analyses are also useful for providing accurate fertilization recommendations and for maintaining or improving soil and environmental sustainability. However, there are forms not immediately available (referred to as non-exchangeable forms) that can interact with the other K pools depending on a series of soil and climate factors, resulting in more or less actual K availability for plants. These factors determine the concordance of the analysis results with the real availability of K for the plants and, therefore, the response to potassium fertilization. The objective of this study was to evaluate soil analysis methods and sample handling (moisture conditions) to more accurately estimate the K available for crops. For this, it was studied how they affect some soil characteristics such as the content and mineralogy of the clay fraction, as well as soil moisture prior to sampling and at the time of its analysis. Different analysis methodologies were adjusted and carried out, which would later be used to evaluate the results of field experiments. Critical levels were obtained for different soil situations, which were higher than those previously reported by other researchers.