Defoliation height and potassium fertilization of Mulato II grass

Abstract

A pot trial in greenhouse conditions was carried out to identify at which defoliation height Mulato II grass (Urochloa hibrida cv. Mulato II) should be managed and to determine whether potassium fertilization is necessary in soil with high potassium content. The experiment was carried out in a greenhouse in a randomized block design with six treatments and five replications. Treatments consisted of a 3 × 2 factorial arrangement, with three defoliation heights (50, 65, and 80 cm) and with or without potassium maintenance fertilization. The production characteristics and chemical composition of the forage plant were evaluated. There was no interaction effect between defoliation height and fertilization with or without potassium on any of the analyzed variables, except for mineral content in Mulato II grass. The tillers and leaves number, shoot dry matter, leaf+sheath, root system, and residue were influenced by defoliation heights and potassium fertilization, except for the leaf blades and root dry matter, leaf blade/stem+sheath ratio, and leaves number, which were not influenced by potassium fertilization. Higher shoot dry matter was observed at the heights of 65 and 80 cm; however, comparing these two heights, leaf + sheath dry matter was lower at 65 cm. Regarding the grass’s chemical composition, there was an increase in neutral and acid detergent fiber and indigestible neutral detergent fiber contents as the defoliation height increased, which resulted in lower production of potentially digestible dry matter, which can compromise the potential use of the forage by animals. Among evaluated treatments, Mulato II grass defoliation is recommended for a maximum height of 65 cm. Potassium fertilization increases the yield and the potentially digestible dry matter content of Mulato II grass, even when cultivated in soil with high potassium content.