Washington navel orange trees on trifoliate orange rootstocks were inoculated at various ages with budwood from either severely dwarfed Washington navel trees with butt scaling caused by exocortis virus or moderately dwarfed Marsh grapefruit trees with no butt scaling. Dwarfing, measured by trunk girth, became apparent four seasons after inoculation, the butt scaling inoculum causing more pronounced dwarfing than the non-scaling inoculum. For both inocula, trees inoculated in the nursery were the most dwarfed, and yielded least, with trees inoculated in the field one, two, three or five years later being successively less dwarfed and high yielding. In a second experiment, Washington navel orange trees on trifoliate orange, which were carrying exocortis virus or were inoculated with it either in the nursery or later in the field, were planted in 1962 at a density of 835 ha-1. The field inoculated trees subsequently grew larger than the others. All were more dwarfed but yielded more heavily on a ground area basis during five years of cropping than exocortis-free trees planted at a normal density of 222 ha-1. Dwarfed trees developed butt scaling symptoms and periodically became unthrifty. The non-scaling form of dwarfing lends itself to the development of high density plantings of small trees with consequent benefits in management and high early production
One hundred and ten paddocks were surveyed to give an overview of the effects of management burning, grazing by cattle, goats and sheep, and protection from livestock, on major vegetation types in the rangelands. A commercial paddock scale was used to complement information previously available on dietary preferences of livestock from a few, small research sites. In this dry period study, estimates of woody and herbaceous cover were not significantly different overall among paddocks subjected to the various kinds of management. However, herbaceous cover in protected or spelled paddocks was better than in the others. Also, no significant relationships were found between woody cover and herbaceous biomass in any treatment. Despite moderate sample sizes, high coefficients of variation occurred throughout the results. These were regarded as being a true reflection of the variability between paddocks in the rangeland. Underlying differences between management types may have been masked by the heterogeneity of the paddocks within each type due to a complex history of rainfall, burning and grazing. Cluster analysis of the 110 paddocks revealed floristic (woody spp.) similarities of mulga, poplar-box, pine and some belah-rosewood woodlands, whereas saltbush and mallee were distinct. Further comparisons of management types were made on mulga woodland alone. Domestic goats were kept in the most heavily wooded paddocks and, in contrast with sheep, checked the growth of woody plants < 2m high. Woody growth recovered in the < 2m stratum several years after burning. Further evaluation of the herbaceous layer and of woody/herbaceous relationships is recommended after a wet summer.
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