Canopy height and N affect herbage accumulation and the relative contribution of leaf categories to photosynthesis of grazed brachiariagrass pastures

Abstract

The effects of three canopy heights (10, 25 and 40 cm) and two N rates (50 and 250 kg ha−1 year−1) on herbage accumulation (HA), participation of leaf categories in the leaf area index (LAI) and photosynthesis of grazed “Mulato II” brachiariagrass (Brachiaria brizantha × B. decumbens × B. ruziziensis) were investigated during two summer growing seasons in Piracicaba, São Paulo, Brazil. The HA and LAI increased linearly from 8560 to 13600 kg DM ha−1 year−1 and 2.3 to 5.5 m2 m−2, respectively, as canopy height increased. Mulato II brachiariagrass maintained at 10 cm canopy height showed greater proportion of young leaves, but was less productive than taller canopies. Taller canopies had greater proportion of mature leaves in the LAI as well as greater photosynthesis. The greater N rate contributed to increased LAI, leaf and canopy photosynthesis rates and HA but did not affect the LAI composition. The total leaf area is more important to HA than the proportion of young leaves in the LAI, as taller canopies were more productive, suggesting that maintaining Mulato II brachiariagrass at 25 or 40 cm is advantageous for this grass.

Unravelling the relationship between a seasonal environment and the dynamics of forage growth in grazed swards

“…The greater SER observed in summer can be associated with the differentiation of the shoot apical meristem, since marandu palisadegrass presented most of visible inflorescence during autumn (visual assessment). During autumn and winter–early spring, it was observed reductions in tissue flows (lower LER and SER [Table 3]; greater SR, PHY and LLS [Tables 3 and 4]) and lower forage accumulation rates (Figure 3), especially on taller treatments; this is because the ageing of photosynthetic apparatus associated with a mild and dry period reduces growth rates and increases leaf senescence as a consequence of the lower photosynthetic efficiency observed under these situations (Braga, Mello, Pedreira, & Medeiros, 2009; Parsons, Leafe, Collett, Penning, & Lewis, 1983; Yasuoka et al, 2018). Therefore, our data demonstrate that: (a) tissue flows in individual tillers are capable of compensating lower TPD and maximizing forage accumulation when environmental conditions are favourable to growth of tropical grasses (warm and rainy periods); and (b) greater TPD is more relevant for forage accumulation under limiting situations (dry and mild periods), since tissues flows are normally reduced in those circumstances.…”

Acumulación de forraje de pasto buffel e híbridos de Urochloa a diferente edad de rebrote

“…La diferencia de los valores obtenidos en AFE entre edades de rebrote se atribuye al aumento en altura conforme avanzó la edad de la planta, lo que ocasionó mayor proporción de hojas maduras y de mayor espesor, en comparación con las hojas jóvenes(Yasuoka et al 2018). Lo que ocasionó disminución en los valores de AFE en edades mayores de rebrote.…”

Production of beef cattle grazing on Brachiaria brizantha (Marandu grass)—Arachis pintoi (forage peanut cv. Belomonte) mixtures exceeded that on grass monocultures fertilized with 120 kg N/ha

“…Nitrogen fertilization of pastures increases the morphogenetic rhythm, density and renewal of plants, which culminates in higher rates of forage accumulation (Paiva et al, 2011;Yasuoka et al, 2018).…”