Stem and pseudostem growth play a key role in biomass accumulation of guineagrass in long regrowth cycles

Abstract

Context Tall bunch-type tropical forage grasses are known for their rapid (true) stem elongation late in the regrowth cycle, even during the vegetative phase. Aims This study aimed to evaluate the stem and pseudostem growth pattern of ‘Mombaça’ guineagrass [Megathyrsus maximus (Jacq.) BK Simon & SWL Jacobs] grown in field conditions and how this relates to its high biomass accumulation during long regrowth cycles. Methods A guineagrass field was managed from December 2017 to January 2019, in three regrowth cycles of 10, 14 and 12 weeks duration. Individual tillers were assessed weekly to measure stem, pseudostem and leaf elongation, leaf appearance; and angle of insertion of the leaves. Aboveground biomass samples were taken weekly for biomass accumulation and leaf area index assessment. Key results At the beginning of each regrowth cycle, the pseudostem elongated while the stem length remained constant. Subsequently, the pseudostem length reached a plateau, while the stem length increased at a constant rate. Because of a positive relationship between pseudostem and leaf laminae lengths, the long pseudostem ensured the formation of long leaves in tall tillers and positive net leaf elongation in long regrowth cycles. Conclusions The high biomass accumulation reflected the continuous positive net leaf elongation by the tillers and was underpinned by the younger leaves being more erect than the older ones, allowing for lower self-shading of the older leaves and greater leaf tissue retention. Implications The high production of tropical forage grasses in late regrowth should be utilised with caution, as it is underpinned by stem elongation and meristem elevation.

Forage accumulation, nutritive value, and grazing efficiency on rotationally stocked ‘Zuri’ guineagrass pastures as affected by pre‐graze canopy height and N rate

“…Pastures grazed at taller pre‐graze canopy height (H75) showed greater FA rate due to the increase of leaf area index and LI, which is directly related to pasture growth (Almeida et al, 2023b) and animal production (Rouquette Jr., 2016). In upright growth grasses like Zuri guinegrass, stem elongation is important due to its contribution in supporting leaves and helping the grass stay erect (Brunetti et al, 2023), as well as increasing FA (Almeida et al, 2023b). The greater presence of lignified stems, however, is usually associated with lesser grazing efficiency (Braga et al, 2007).…”

Defoliation management and nitrogen fertiliser rate affect canopy structural traits of grazed guineagrass (Megathyrsus maximus) cv. Zuri under rotational stocking

“…2015). Above 95% LI, stem elongation increases, and this has been associated with intra-specific competition for light among individual plants and an increase in dead material accumulation due to mutual shading (Brunetti et al . 2023).…”

“…During the rest period after grazing, the grass canopy reaches a point where the maximum leaf accumulation has been associated with 95% light interception (LI) (Silva et al 2015). Above 95% LI, stem elongation increases, and this has been associated with intra-specific competition for light among individual plants and an increase in dead material accumulation due to mutual shading (Brunetti et al 2023).…”