ABSTRACT: Enhanced efficiency potassium fertilizers can be a management tool that is crucial to crop sustainability in maize (Zea mays L.). However, there is a need for studies aimed at validating the use of these fertilizers in different production environments. This study aimed to evaluate the performance of maize under sources and rates of K through conventional and enhanced efficiency fertilizers in soil with high available K content. The experiment was carried out for two years in an Oxisol (605 g kg–1 of clay) with high K content (6.7 mmolc dm–3). Three sources were used, one conventional (KCl), one obtained by additives sprayed on the fertilizer surface (KCl-C), and one obtained by compacting KCl powder and adding additives (KCl-CC), associated with three K2O rates as top-dressing (50, 100, 150 kg ha–1) and a control without K2O. In all treatments, 48 kg ha–1 of K2O was applied in the sowing furrow. In the first year, maize yield increased linearly for both the KCl and KCl-C sources. The maximum yield (7,967 kg ha–1) for the KCl-CC was obtained at 88 kg ha–1. In the second year, the maximum yields for the KCl (7,553 kg ha–1) and KCl-C (8,166 kg ha–1) were obtained with 20 and 67 kg ha–1 K2O, respectively, while for the KCl-CC maize yield did not change. Enhanced efficiency K sources promote increases in maize yield ranging from 4.3 % to 7.1 %. Top-dressing K fertilization in high-fertility soils is a viable alternative for producers focused on increasing maize yield, mainly when enhanced efficiency sources are used.

RESUMO O uso de fertilizantes revestidos é uma estratégia para melhorar a eficiência da adubação e o rendimento das culturas. No entanto, são necessários estudos para entender a dinâmica no solo dos diferentes tipos de fertilizantes potássicos (K) revestidos. Objetivou-se avaliar a lixiviação, disponibilidade e recuperação de K em colunas de solo após aplicação de fonte convencional KCl e outras fontes de K com tecnologias de revestimento e compactação. O experimento compreendeu quatro tratamentos, constituídos por três fontes de K (KCl convencional; KCl revestido com aditivos e polímeros - KCl-C; e KCl compactado e revestido com aditivos e polímeros - KCl-CC), e um controle sem adubação, com quatro repetições. Os teores de K foram avaliados na solução lixiviada das colunas de solo por 28 dias. Após esse período, foram determinados os teores de K no solo. A ausência de adubação no solo levou a uma redução de 26,5% nos teores de K. As fontes revestidas apresentaram menor dureza de grânulos e maior lixiviação de K em relação ao KCl convencional. A quantidade de K lixiviada foi de 62,2% para KCl-CC, 68,5% para KCl-C e 54,0% para KCl convencional. No entanto, ao final do experimento, os teores de K no solo foram maiores para a fonte KCl-C.

ABSTRACT The use of coated fertilizers is a strategy for improving fertilization efficiency and crop yield. However, further studies are needed to understand the dynamics of different types of coated K fertilizers in the soil. The objective of this study was to evaluate K dynamics in soil columns after the application of conventional KCl and other K sources with coating (KCl-C) and compaction (KCl-CC) combined with the use of additives and polymers. The experiment comprised four treatments, consisting of three sources of K [conventional KCl, KCl coated with additives and polymers (KCl-C), and KCl compacted and coated with additives and polymers (KCl-CC)], and a control without K application, with four repetitions. The K concentration was evaluated in the leached solution collected from the soil columns for 28 days. After this period, the K concentration in the soil was determined. The absence of K fertilization in the soil led to a 26.5% reduction in the K concentration. The coated sources had lower granule hardness and higher K leaching than conventional KCl. The amounts of K leached were 62.2%, 68.5%, and 54.0% for KCl-CC, KCl-C, and conventional KCl, respectively. However, at the end of the experiment, the soil K concentration was higher under the KCl-C treatment.