Tillering dynamics of ‘Mulato II’ brachiariagrass under continuous stocking

Abstract

AbstractLong‐term stand persistence is a desirable characteristic of sustainable grassland ecosystems, and tillering dynamics is an important determinant of persistence. Grazing intensity and nutrient supply affect tiller density, weight, and survival. Understanding the relationships among these factors can help optimize performance of grazed pastures. The objective of this research was to determine the effects of canopy height (10, 25, and 40 cm; maintained under mimicked continuous stocking) and N fertilization (50 and 250 kg ha−1 yr−1) on the tiller dynamics and canopy stability index (SI) of ‘Mulato II’ hybrid brachiariagrass (Brachiaria spp. syn. Urochloa spp.) during two growing seasons. Tiller population density (TPD) increased by 9% with greater N fertilization and decreased linearly from 1,130 to 900 tillers m−2 as canopy height increased from 10 to 40 cm. Tiller weight (TW) increased from 0.39 to 1.46 g as canopy height increased from 10 to 40 cm, but TW decreased by 9% with a greater N rate. Tiller appearance rate increased by 30% and tiller survival rate (TSR) decreased by 13.5% as N rate increased. The TSR was greater for 25‐ and 40‐cm than for 10‐cm canopies (81, 82, and 74 tillers per 100 tillers per 30 d, respectively). The SI increased from 0.91 to 1.0 with increasing canopy height from 10 to 40 cm. Mulato II canopies followed the tiller size–density compensation mechanism, displaying phenotypic plasticity in response to canopy height, but these results suggest a 25‐cm canopy height is near optimal for continuously stocked Mulato II brachiariagrass pastures.