Components of herbage accumulation in elephant grass cvar Napier subjected to strategies of intermittent stocking management

Abstract

SUMMARYHerbage accumulation is determined by the tissue turnover of individual plants and by the regulation patterns of the number of individuals in a plant population, which function in conjunction to enable swards to adapt to variations in growth and management conditions. Based on the hypothesis that intermittent grazing strategies change the proportion of basal and aerial tillers and, consequently, sward herbage accumulation, the objective of the current experiment was to evaluate the components of herbage accumulation in elephant grass cvar Napier (Pennisetum purpureum Schum. cvar Napier) from January 2011 to April 2012. The treatments corresponded to combinations of two post-grazing (post-grazing heights of 35 and 45 cm) and two pre-grazing conditions (0·95 and maximum canopy light interception during regrowth – LI0·95 and LIMax) and were allocated to experimental units (850 m2 paddocks) according to a 2×2 factorial arrangement in a complete randomized block design with four replications. The following response variables were evaluated: the population density of basal tillers (TPDb) and the population density of aerial tillers (TPDa), the number of aerial tillers per supporting unit (A/B+VC), growth rates of the leaf (LGR) and stem (SGR), leaf senescence rate, net leaf accumulation rate (LAR), and the contributions of basal and aerial tillers to sward growth and senescence. The swards managed with the LI0·95 target had greater TPDb than those managed with the LIMax target, but no difference was recorded between the LI pre-grazing targets for TPDa. The larger A/B+VC ratio recorded for the swards managed with the LIMax target resulted in a higher contribution of aerial tillers to the growth and senescence of swards. This growth strategy resulted in a higher SGR and lower LGR and LAR for the swards managed with the LIMax target relative to those managed with the LI0·95 target. The post-grazing height targets affected only LGR during winter and the second summer and SGR on average for the experiment, with higher values recorded for the swards managed at 35 cm. The LI pre-grazing targets played a central role in defining the compensatory mechanisms responsible for the competitive ability of the plants, which were primarily expressed in the variation of the proportion of basal and aerial tillers in the tiller population and interfered with the components of herbage accumulation and total herbage yield of the swards.

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

“…Aruana [93], and Pennisetum purpureum cv. Napier [94,95], showing consistency within a wide range of morphological types and a strong light effect determining plant growth. More recently, in a study where a forage grass (Brachiaria brizantha cv.…”

“…In addition, long grazing intervals characterized by the pre-grazing target of LImax result in a greater proportion of the produced herbage being lost to the soil as a consequence of physical damage and/or rejection, decreasing the efficiency of the grazing process [85,90,91]. The investment in stem elongation results in taller swards with an increased proportion of stems in the upper layers of their vertical profile [92], increasing the difficulty of grazing and in maintaining the post-grazing management targets [93,94]. As a result, the benefit of greater total herbage accumulation is offset by the greater grazing losses when long regrowth intervals are used, indicating that, although herbage accumulation per grazing cycle is smaller when managing with shorter grazing intervals (LI95%), the more frequent defoliation results in larger number of grazing cycles and total herbage accumulation (with higher leaf proportion) than when managing with longer grazing intervals (LImax) [84,91,94,95].…”

“…A more uniform ground cover with smaller tussocks, greater tiller population density, and short distances between tussocks results in more efficient sward carbon acquisition [115] and may also minimize weed encroachment [116]. More recently, new evidence on modification of sward horizontal structure in adaptation to grazing management was reported by Pereira et al [94,95] for rotationally managed Napier elephant grass (Figure 2). The authors showed that grazing management interfered with the vegetative mechanism used by plants for perennation by altering the number and the proportion of aerial and basal tillers in tiller population, with consequences on sward horizontal structure and herbage accumulation.…”

<b>Sward structure, light interception and herbage accumulation in forage peanut cv. Belmonte subjected to strategies of intermittent grazing management

“…Greater LI values during regrowth were obtained with greater forage height values (13.0 and 18.0 cm for IL 95% e IL Max , respectively; Table 2). The difference between heights associated to LI targets was of 5 cm, which is much lower than previously observed for tropical grasses, such as mombaça grass (25 cm; Carnevalli et al (2006), tanzânia grass (15 cm; Barbosa et al (2007), xaraés grass (10 cm; Pedreira, Pedreira, and Silva (2007)), marandu grass (10 cm; Trindade et al (2007), mulato grass (10 cm; Silveira et al (2013) and napier grass (40 cm; Pereira, Paiva, Geremia, and Silva (2014). This difference was likely due to the more horizontal leaf structure of legumes as compared to grasses.…”

Acúmulo de forragem e estrutura do dossel de Capim-Marandu diferido e adubado com nitrogênio

“…No interior de dosséis altos, ocorre maior sombreamento, o que gera competição entre os perfilhos por luz. Como resposta, os perfilhos alongam seu colmo a fim de expor as novas folhas na porção superior do dossel, onde a luminosidade é maior (PeReiRa et al, 2014 Com o maior crescimento da planta adubada com 200 kg de N/ha, é natural que sua biomassa seja constituída por maior percentagem de colmo vivo, em relação às plantas adubadas com menor dose de nitrogênio (Tabela 4). A planta com maior taxa de crescimento alcança maior peso, o que requer um órgão estrutural, o colmo, mais desenvolvido para sustentar os perfilhos mais compridos e pesados.…”