Canopy structure of mixed kikuyugrass–tall fescue pastures in response to grazing management

Abstract

ABSTRACTThe effects of different management strategies on improving growth and modifying the botanical composition of C3 and C4 perennial grasses grown in a mixed canopy are underexplored. We aimed to evaluate the botanical composition and vegetation dynamics of a mixed canopy containing kikuyugrass (Pennisetum clandestinum Hochst. Ex Chiov) and tall fescue (Festuca arundinacea Schreber cv. Rizomat) subjected to four grazing management strategies over 22 mo. The experimental design was a randomized complete block in a factorial arrangement (two maintenance canopy heights: grazed to 7 cm in the autumn, or uninterrupted and maintained at 12 or 17 cm) with three replicates. The plots were sampled every month throughout the experimental period; the forage mass data were used to determine the botanical composition and leaf area index of the canopy. Although autumn grazing to 7‐cm height promoted an increase in pasture leaf proportion, it did not represent an effective augment in pasture leaf mass in the following winter–spring season. Canopies heights managed at 17 cm presented a greater proportion of tall fescue in herbage mass (81%) compared with those maintained at 12 cm (73%). Severe defoliation in the autumn delayed the regrowth to 12‐ or 17‐cm canopy heights by approximately 90–120 d in both evaluation years. From a farm‐level perspective, this result would restrict the recommendation of this grazing management strategy because this time lapse would demand that the pastures not be grazed for the 25–33% period of the year compared with the pastures that were not grazed in the autumn.