Size/density compensation in Chloris gayana Kunth cv. Fine Cut subjected to different defoliation regimes

Abstract

The study evaluated the plasticity of Chloris gayana Kunth cv. Fine Cut to defoliation in terms of tiller size ⁄ density compensation (SDC). Twelve mini-swards were grown in a greenhouse under non-limiting water and nutrient availabilities for 188 d. Four defoliation treatments were applied as a factorial arrangement of two defoliation frequencies and intensities: 80L, 80H, 100L and 100H (80 and 100 denote percentage of photosynthetically active radiation intercepted at defoliation; L and H denote stubble LAIs of 0AE6 and 1AE75, respectively). Tiller density, demography, dry weight, leaf area and volume were determined over the final 77 d of the experiment. SDC was observed across 80H and both 100 treatments. The estimated slope of the relationship between tiller size and density was close to )5 ⁄ 2, the deviation from the )3 ⁄ 2 line proposed for undefoliated swards being related to changes in LAI and tiller leaf area ⁄ volume ratio. The most severe defoliation regime, 80L, resulted in a lower tiller population density relative to the compensation line, suggesting that this defoliation management shifted the species beyond its range of phenotypic plasticity. Cumulative herbage production was significantly reduced in 80L. Despite the similar herbage production of 80H and both 100 treatments, the former was the most favourable defoliation regime for optimizing leafiness and productivity.

Persistence and productivity of orchardgrass and orchardgrass/alfalfa mixtures as affected by cutting height

“…Here, we found the slope of the apparent SDC line to be −1·778, somewhat steeper than −3/2. This matches with SDC slopes greater than −3/2 found for perennial ryegrass (Hernandez Garay et al., ) and rhodesgrass (Martinez Calsina et al., ).…”

“…The distance that otherwise similar treatments fall from a SDC line can be used as a measure of relative sward productivity (Hernandez Garay et al., ; Martinez Calsina et al., ). The 10‐, 15‐ and 20‐cm treatments were located along the apparent SDC slope found in this experiment while the 5‐cm treatment deviated from this line in the negative direction.…”

“…It has been theoretically shown (Matthew et al., ) and experimentally confirmed (Hernandez Garay et al., ) that the distance a treatment lies from an arbitrarily placed SDC line with slope −3/2 provides a measure of relative stand productivity. The slope of the SDC line is also known to be steeper (closer to −5/2) in defoliated swards (Martinez Calsina et al., ; Matthew et al., ). The slope of the apparent SDC line was calculated by major axis regression of the log tiller weight by log tiller density for the 10‐ to 20‐cm cutting height treatments.…”

“…This has been implemented in several forage systems including perennial ryegrass ( Lolium perenne L.) mini‐swards (Hernandez Garay et al., ), rhodesgrass ( Chloris gayana Kunth.) mini‐swards (Martinez Calsina, Agnusdei, Assuero, & Perez, ), field‐grown tall fescue ( Schedonorus arundinaceus (Schreb.) Dumort.)…”

Efficiency and stability in subtropical beef cattle grazing systems in the northwest of Argentina

“…Certain components in the model rely on empirical parameters, requiring site-specific calibration (Romera et al, 2009). Range of parameter values for tropical pastures, and specifically for C. gayana pasture were taken from literature review Avila et al, 2012;Martínez Calsina et al, 2012;Moser et al, 2004). Calibration was performed by altering the values of parameters in order to obtain the best fit between the simulate outputs and measurements made in real systems (Ahuja and Ma, 2002;Carlson et al, 1993).…”