TILLER DYNAMICS OF Urochloa HYBRID GRASS CV COBRA IN RESPONSE TO CUTTING TIME

Abstract

The Urochloa hybrid grass cultivar Cobra was recently introduced to the Mexican tropics and the dynamics of the life cycle of its tillers, an aspect related to forage production and persistence, is largely unknown. The aim od this study was to evaluate its performance at four cutting times. It was hypothesized that carrying out forage cuttings based on the amount of light intercepted by the canopy favors dynamics. The treatments applied were cuts when reaching 90, 95 and 100 % of light interception (LI) and a cut at a fixed time. The trial was established in 2017 under a randomized complete block design with four replications in Medellín, Veracruz, Mexico. Tillers were counted monthly in circles of 20.32 cm in diameter. Tiller emergence (TER), survival (TSR) and death (TDR), as well as stability index (SI) were not affected (P > 0.05) by time to cut; the greatest effect was due to the season of the year (P ≤ 0.001) and there was only season × treatments interaction for TER and SI (P ≤ 0.04). TER and TSR were thigher (P ≤ 0.05) in Summer and Fall between 62 and 76 %. The lowest TDR (P ≤ 0.05) was in Summer and reached 43 %. The tiller population density (TDP) was affected by time to cut (P ≤ 0.0001) and season (P ≤ 0.0001), it was found that cutting at 90 % LI induced the highest TPD (P ≤ 0.05) with 2048 stems m^-2, while cuttings at a fixed time and at 100 % LI had the lowest (882 and 1271 stems m^-2, respectively). Tiller dynamics in this grass is mostly influenced by environmental conditions according to the season of the year; however, cutting at 90 % IL induces greater TPD.