Do enhanced efficiency potassium sources increase maize yield in soil with high potassium content?

: 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 mmol c 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 K 2 O rates as top-dressing (50, 100, 150 kg ha –1 ) and a control without K 2 O. In all treatments, 48 kg ha –1 of K 2 O 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 K 2 O, 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.