Extensive work has been carried out to determine the management strategies that best control 'Nassella trichotoma' (serrated tussock) throughout the south eastern regions of Australia and New Zealand. 'N. trichotoma' infested areas on the Northern Tablelands of New South Wales (NSW) in the early 1960s and it went unnoticed and uncontrolled for many decades. Since the recognition of 'N. trichotoma' on the Northern Tablelands as a weed of significance, measures have been taken for its control and management. Many of the ideas for control have been taken from the practices that are used on current infestations in the south eastern areas of Australia and in New Zealand. The variation in the environmental conditions and characteristics of infestations between these southern areas and the Northern Tablelands are the motive for development of more specific management options.

Quantifying spatial variation in pasture and crop biomass can help to direct management practices and improve farm productivity, through accurate and informed movements of grazing rotations, crop and pasture nutrient management and yield production. Visual pasture assessments are often subjective, and require a degree of expert knowledge/experience. Quadrat-based plant harvesting determinations of biomass is labour intensive and costly when accurate quantification of pasture and crop variability over large areas is required. Furthermore, quadrats of 1m² or less are not easy to relate to remotely sensed images with spatial resolutions ranging from 4 to 400m². Active optical plant sensors that measure the red and near-infrared radiation reflected from the vegetation canopy offer the potential of deriving objective estimates of the photosynthetically-active plant biomass and may also hold the key to quantifying biomass over large areas with high spatial resolution. Crop Circle™ (Holland Scientific) is one example of an active plant sensor that measures red and near infrared light reflected from the canopy/soil matrix. In this paper we present the results of a project to assess the accuracy of Crop Circle™ for biomass assessment in a variety of agricultural environments including: native, improved and irrigated pasture; and forage and cereal crops.

Longwall mining generally results in subsidence of the land surface. While the extent and nature of subsidence on surface topography is reasonably well understood the effects on surface environments (agricultural and native vegetation) arc less well known. In this paper we will describe the initial stage of a three year ACARP project to develop scientific protocols to quantify changes to above-ground environments. Specifically, the project objectives are to: quantify the effects of longwall mine subsidence on agricultural and terrestrial native vegetation; develop industry-standard methods for monitoring these effects; optimise monitoring quality, quantity, safety aspects, timeliness and cost effectiveness through the integration of high resolution remote sensing and ground-based sampling.

Serrated tussock ('Nassella trichotoma' (Nees) Arechav.) is a perennial grass weed of pastures. It is a widespread problem on the Southern Tablelands of New South Wales (NSW) that have a Mediterranean climate and is now invading the Northern Tablelands of NSW where rainfall is summer dominant. Isolated infestations are found under trees and in open areas. Due to the importance of wind-borne seeds to the invasive capability of serrated tussock and the suppression of seeding in effective management, it is necessary to understand when plants set seed and the factors that affect the level of seed production. In particular a reduction in the intensity or amount of light received by a plant can have implications on physiological responses such as changes in seed production. The aim of this study was to assess the effect of shade on the timing and amount of seed production.