Efeito residual no solo do uso de polihalita na adubação de soqueira de cana-de-açúcar

ABSTRACT Polyhalite is a potential alternative source of potassium (K) for sugarcane cultivation. Its lower solubility, compared to potassium chloride (KCl), suggests it may act as a slow-release fertilizer, providing residual benefits to subsequent crops. This study aimed to assess the residual effects of polyhalite on the soil following two cycles of potassium fertilization in ratoon cane, in comparison with KCl. The treatments included a control (no K fertilization) and K sources applied individually (polyhalite or KCl) or in combination (polyhalite + KCl). The polyhalite performed similarly to KCl and led to the highest K levels in the 0-20 cm soil layer after two sugarcane harvests. For the sulfur (S) content, the polyhalite significantly outperformed all other treatments, with the highest concentrations in the 0-20 and 20-40 cm layers. On the other hand, the supply of calcium and magnesium from polyhalite did not result in higher soil levels of these nutrients, with no significant differences among the evaluated sources. These findings highlight the residual benefits of polyhalite application, particularly for S, which may be beneficial for sugarcane or any subsequent crops.