EFFECT OF HERBAGE REJECTION BY STEERS ON WHITE CLOVER (TRIFOLIUM-REPENS) BRANCHING AND DEVELOPMENT IN CONTINUOUSLY STOCKED GRASS-CLOVER SWARDS

The proportion of sward area rejected for grazing under different stoc king intensities in grass-white clover (Trifolium repens L.) swards co ntinuously grazed by steers to constant sward height was determined an d the effect of these areas on clover stolen development was investiga ted. In a randomized block field experiment, grazing treatments impose d from 1988 to 1991 comprised target sward surface heights (SSH) of 5, 7 or 9 cm from April to July followed by 7 or 9 cm from July to Octob er (i.e. six treatments). The percentage area rejected was higher in 9 cm than in the shorter swards, the proportion of the total areas reje cted increasing generally over the year. Within the rejected areas in spring the number of branches on the main axes of white clover plants was only 17% and the mean number of nodes per branch was 14% of those in grazed areas. Corresponding percentages in summer in rejected areas were 56 and 46% compared with grazed areas. In a glasshouse experimen t involving stolons grown for 18-21 days, the difference between those from grazed and rejected areas in branch number per stolen and mean n ode number per branch was much reduced, Branching and rate of branch d evelopment (node number) were slower in stolons maintained under dark conditions. Mean growing point density over six sampling dates from su mmer 1990 to autumn 1991 was significantly higher in the 5 cm than in the 9 cm spring SSH treatment. Although rejected areas had only 34% of the growing point density of grazed areas in autumn, the latter compr ised the majority of the total area in most sward height treatments an d so reduced the overall effect of rejected areas on growing point den sity.