The influence of grazing interval and perennial grass species on soil moisture.

To examine interactions between perennial grass species and grazing management, phalaris, cocksfoot, tall fescue and wallaby grass were grazed by sheep at intervals of 2, 5 or 8 weeks over the spring-autumn periods of 1994/5 and 1995/6. For simplicity sake, only the two most widely differing species, phalaris and wallaby grass, are presented. Soil moisture was monitored to 150 cm using a neutron moisture meter. The results depended on the season, 1994/5 being much drier than 1995/6. In 1994/5 there was a significant grazing by species interaction with wallaby grass more effective at drying the profile than phalaris when grazed every 2 and 5 weeks and phalaris more effective than wallaby grass when grazed every 8 weeks. This was mainly due to changes in the profile over 0-90 cm depth, below this there was only a minor but significant effect of species. Overall, there was no interaction between grazing interval and species. In the wetter 1995/6 season, total soil moisture was significantly lower under the 5 and 8 week grazing regimes compared to the 2 week grazing interval. This result largely reflected that for the 0-90 cm section of the profile. In the 90-153 cm section of the profile there was also a significant grazing by species interaction evident. By May 1996, soil under plots that had been grazed every 5 or 8 weeks was at least 22 mm drier compared to those grazed every 2 weeks. By implication, the magnitude of the advantage of perennial species over annual species in drying soil profiles will depend in part on the grazing management of the pasture.