Abstract
Several compensatory mechanisms in pastures do not allow optimisation of responses from the processes of herbage production and utilisation. Compensation due to tiller size/density relationships is one of these mechanisms. This experiment evaluated this process for Coastcross bermudagrass and compared the responses to those reported for temperate forages. Treatments were "steady state" sward surface heights of 5, 10, 15, and 20 cm that were maintained from August, 1998, through July, 1999 by sheep grazing. The experimental design was a randomised complete block, replicated four times. Pasture responses were evaluated on four separate dates (15/12/1998, 25/01/1999, 07/04/1999 and 04/07/1999) with respect to: tiller population density, tiller weight, leaf mass and leaf area per tiller and herbage mass (biomass). Tiller volume, leaf area index (LAI), tiller leaf:stem ratio and tiller leaf area:volume ratio (R) were calculated. Simple regression analyses between tiller population density and tiller weight were also performed. Coastcross swards showed a tiller size/density compensation mechanism where high tiller population densities were associated with small tillers and vice-versa; except on the last evaluation. However, regression analysis revealed linear coefficients of -3.83 to -2.05, which are lower than the theoretical expectation of -3/2. The lower R values observed, when compared to those reported for perennial ryegrass, suggest that Coastcross swards optimised their LAI via clonal integration among tillers in contrast with tillers of cool-season grasses that respond more as individuals. However, this hypothesis has yet to be experimentally verified.
Highlights
Pastures are characterised by a complex integration of factors that result in very specific and dynamicScientia Agricola, v.58, n.4, p.655-665, out./dez. 2001 patterns of responses
Swards maintained at 10 cm during evaluation 3 presented a Tiller population density (TPD) higher than those kept at 5 cm, indicating that Coastcross swards were not able to compensate the reduced sward surface height (SSH) by increasing tiller numbers
The tiller size/density compensation mechanism originally described for temperate forage plants operates in Coastcross pastures
Summary
Pastures are characterised by a complex integration of factors that result in very specific and dynamicScientia Agricola, v.58, n.4, p.655-665, out./dez. 2001 patterns of responses. In grass swards there are several compensatory mechanisms operating and “buffering” overall responses in terms of herbage production and utilisation. Among these processes, tiller size/population density compensation (SDC) is one of the most intriguing mechanisms and has been studied intensively during recent years (Matthew et al, 1995; Sackville Hamilton et al.,1995; Hernández Garay et al, 1999). Pastures are a population of single tillers (Mitchell & Glenday, 1958; Korte, 1986; Colvill & Marshall, 1984) which implies that increases in herbage production can be generated from increases in tiller numbers, tiller weight or a combination between them (Nelson & Zarrough, 1981; Bircham & Hodgson, 1983; Grant et al, 1983; Volenec & Nelson, 1983). Tillers are subjected to a SDC mechanism which leads to a small population density of large tillers under lenient defoliation or a high population density of small tillers under intense defoliation (Bircham & Hodgson, 1983; Grant et al, 1983; Matthew, 1992; Hernández Garay et al, 1999)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
