Dynamics of sward condition and botanical composition in mixed pastures of marandugrass, forage peanut and tropical kudzu

Abstract

-This study was carried out to evaluate the dynamics of sward condition and botanical composition of a mixed pasture of marandugrass (Brachiaria brizantha cv. Marandu), forage peanut (Arachis pintoi cv. Mandobi) and tropical kudzu (Pueraria phaseoloides), rotationally stocked at four daily forage allowance levels (6.6, 10.3, 14.3 and 17.9% of live weight). Sward condition was characterized in each stocking cycle by measuring pre-and post-grazing sward height, forage mass and percentage of bare ground. Botanical composition (grass, forage peanut, tropical kudzu and weeds) was evaluated before each stocking period. Swards under smaller forage allowances presented lower height, forage mass and ground cover.This condition favored the growth of forage peanut, which constituted 21.1, 15.2, 8.4 and 3.8% of forage mass in the last quarter of the experimental period, from the lowest to the highest forage allowance, respectively. Tropical kudzu was sensitive to all forage allowance levels and its percentage in the botanical composition was strongly reduced along the experimental period, especially during the dry season (July to September). Forage peanut cv. Mandobi and marandugrass form a more balanced mixture when pre-grazing sward height is maintained shorter than 45 cm. Tropical kudzu is intolerant to intensive grazing management systems when associated to marandugrass.

Productivity, utilization efficiency and sward targets for mixed pastures of marandugrass, forage peanut and tropical kudzu

“…Seasonal variation in grazing depth differed from that observed for defoliation intensity, especially in relation to the values obtained in the JanuaryMarch period ( Figure 2D), which were higher due to plant lodging that occurred in the first two stocking cycles. This was a consequence of excessive sward height (78 cm) at the beginning of the experimental period (Andrade et al, 2012). This indicates that defoliation intensity was a more efficient indicator of the relative pasture utilization efficiency for the conditions of this study.…”

“…Therefore, the decrease in defoliation intensity during the driest period of the year seems to have been caused by a combination of these two factors, since there was a lower proportion of leaves in the sward during the period of lower growth, when lower stocking densities were also used due to a reduction in pregrazing forage mass (Andrade et al, 2012).…”

“…Mandobi. The local environmental conditions were described by Andrade et al (2012). Triple super phosphate (50 kg/ha of P 2 O 5 ) was applied to the pasture at the beginning of the experiment.…”

“…Sward height and forage mass were characterized immediately before and after each stocking period as described by Andrade et al (2012). Dry matter (DM) accumulation rates (kg/ha/day), in each stocking cycle, were calculated dividing total forage mass (kg/ha of DM) accumulated during the rest period by the length of this period (days).…”

“…Conversely, forage peanut reaches a more equilibrated mixture with marandugrass when the sward is managed under pre-grazing height below 45 cm (Andrade et al, 2012). However, additional factors need to be considered in the definition of grazing management strategies.…”