Ecophysiology of C4 Forage Grasses—Understanding Plant Growth for Optimising Their Use and Management

Abstract

Grazing management has been the focus of the research with forage plants in Brazil for many years. Only in the last two decades, however, significant changes and advances have occurred regarding the understanding of the key factors and processes that determine adequate use of tropical forage plants in pastures. The objective of this review is to provide an historical overview of the research with forage plants and grasslands in Brazil, highlighting advances, trends, and results, as well as to describe the current state of the art and identify future perspectives and challenges. The information is presented in a systematic manner, favoring an integrated view of the different trends and research philosophies. A critical appraisal is given of the need for revision and change of paradigms as a means of improving and consolidating the knowledge on animal production from pastures. Such analysis idealizes efficient, sound and sustainable grazing management practices necessary to realize the existing potential for animal production in the tropics.

Tiller density and tillering on Brachiaria brizantha cv. Marandu pastures inoculated with Azospirillum brasilense

“…During autumn/winter and early spring the tiller survival increases, although not enough to offset a reduction in the tiller appearance, and the density of the tiller population decreases. Such variations in the tillering dynamics represent a natural cycle of plant growth throughout the year, and they occur regardless of the grazing strategy, grazing method, and fertilization level (Caminha et al, 2010;Silva et al, 2015).…”

“…According to Silva et al, (2015), periods of high availability of climatic growth factors (e.g., temperature and rainfall), as in late spring and summer, are characterized by high rates of tiller appearance and death, and therefore, short-lived generations. However, the balance between the tiller appearance and death is usually positive and results in an increased tiller population density.…”

Forage Plant Ecophysiology: A Discipline Come of Age

“…Principles of tiller size density compensation [26] are confirmed to apply to both temperate and tropical swards, but the larger tillered tropical grasses tend to be tussock-forming with a size density compensation able to occur both in terms of size and density of tussocks and of tiller size within tussocks. Despite these generalisations, the authors note a very wide variation in morphology and behaviour among the tropical grass species [25].…”

“…Compared to temperate pastures, tropical grass swards have large numbers of aerial tillers (which can be assumed to contribute to rapid leaf area recovery in early regrowth) and are prone to vegetative stem elongation at canopy closure. Hence, infrequent defoliation maximises herbage dry matter production but at a cost to sward quality; conversely, more frequent defoliation delivers reduced dry matter yield but a higher proportion of dry matter production as leaf [25]. Principles of tiller size density compensation [26] are confirmed to apply to both temperate and tropical swards, but the larger tillered tropical grasses tend to be tussock-forming with a size density compensation able to occur both in terms of size and density of tussocks and of tiller size within tussocks.…”

“…Accordingly, one contribution in this volume [25] seeks to review the state of knowledge relating to sward dynamics of tropical grass species, with particular reference to the genera Brachiaria, Pennisetum, and Panicum (tussock forming grasses), as well as Cynodon dactylon (L.) Pers. (a species with a creeping habit spreading by stolons and rhizomes).…”