The Occurrence and Causes of Pasture Pulling Under Dairy Farming on Pumice Soils

The occurrence, and causes, of pasture pulling under dairy farming on Orthic Pumice Soils (Typic Udivitrands) in the central North Island of New Zealand was investigated. Pasture pulling occurs on Pumice Soils, where dairy cows pull clumps of pasture from the soil, thus diminishing pasture production. The overall objective of this study was to investigate the occurrence, and establish the causes, of pasture pulling under dairy farming on Orthic Pumice Soil in the Central North Island, New Zealand. Fifteen paddocks containing pasture of differing ages were investigated at Pouakani dairy farm near Mangakino. Soil profile descriptions were undertaken, and samples were taken seasonally to monitor root depth and density, soil macrofauna, soil dry bulk density, and penetration resistance. Pasture pulling was monitored every 3 weeks by recording the number and size of pulls in a 4 m² quadrant at five points equally spaced along a transect in 15 paddocks. Pasture pulling was recorded in all paddocks and occurred throughout the year, but was most common during the late summer and autumn. Up to 80 % of the root biomass was in the 0-5 cm depth. The 5-10 cm depth generally showed increased compaction with higher soil dry bulk density and penetration resistance then the surface soil. Pastures in isolated clumps were more commonly pulled than more evenly spread pastures. There was an interaction between pasture age and size of pulls, with more medium and large sized pulls in the younger (1-3 year old) pastures. Although anecdotal evidence reports worse pulling in younger pastures, we did not find strong evidence for that assertion. Pasture pulling in 2014 at Pouakani dairy farm was not more obviously impacted by insects. Grass population numbers were uniformly low, and black beetle was rarely seen. Perennial ryegrass was dominant in all paddocks. The paddocks with older, more established pastures contained a higher proportion of other grass species and weeds. Only grass was pulled, other species such as clover, chicory and weeds were not pulled by grazing stock. A pasture pulling index, created to account for the size distribution of the pulls, was more effective at illustrating the seasonal trends associated with pasture pulling than the mean total pulls per quadrat. Overall, the pasture pulling was not severe at Pouakani Dairy farms in 2014. This study has not discovered one sole cause of pasture pulling at Pouakani dairy farms, but has identified a number of soil characteristics that may be contributing, including; limited rooting depth, low root density in the 5-10 cm depth, increased compaction with depth, less cohesive soil when it has low moisture, and the incidence of pasture growing in clumps