Selective herbicide strategies for use in Australian desmanthus seed crops

Grass and broad-leaved weeds can reduce both yields and product marketability of desmanthus (Desmanthus virgatus) seed crops, even when cultural control strategies are used. Selective herbicides might economically control these weeds, but, prior to this study, the few herbicides tolerated by desmanthus did not control key weed contaminants of desmanthus seed crops. In this study, the tolerance of desmanthus cv. Marc to 55 herbicides used for selective weed control in other leguminous crops was assessed in 1 pot trial and 3 Queensland field trials. One field trial assessed the tolerance of desmanthus seedlings to combinations of the most promising pre-emergent and post emergent herbicides. The pre-emergent herbicides, imazaquin, imazethapyr, pendimethalin, oryzalin and trifluralin, gave useful weed control with very little crop damage. The post-emergent herbicides, haloxyfop, clethodim, propyzamide, carbetamide and dalapon, were safe for controlling grass weeds in desmanthus. Selective post-emergence control of broad-leaved weeds was achieved using bentazone, bromoxynil and imazethapyr. One trial investigated salvaging second-year desmanthus crops from mature perennial weeds, and atrazine, terbacil and hexazinone showed some potential in this role. Overall, our results show that desmanthus tolerates herbicides which collectively control a wide range of weeds encountered in Queensland. These, in combination with cultural weed control strategies, should control most weeds in desmanthus seed crops

Blind estimation of reverberation time in classrooms and hospital wards

This paper investigates blind Reverberation Time (RT) estimation in occupied classrooms and hospital wards. Measurements are usually made while these spaces are unoccupied for logistical reasons. However, occupancy can have a significant impact on the rate of reverberant decay. Recent work has developed a Maximum Likelihood Estimation (MLE) method which utilises only passively recorded speech and music signals, this enables measurements to be made while the room is in use. In this paper the MLE method is applied to recordings made in classrooms during lessons. Classroom occupancy levels differ for each lesson, therefore a model is developed using blind estimates to predict the RT for any occupancy level to within ±0.07s for the mid-frequency octave bands. The model is also able to predict the effective room and per person absorption area. Ambient sound recordings were also carried out in a number of rooms in two hospitals for a week. Hospital measurements are more challenging as the occurrence of free reverberant decay is rarer than in schools and the acoustic conditions may be non-stationary. However, by gaining recordings over a period of a week, estimates can be gained within ±0.07 s. These estimates are representative of the times when the room contains the highest acoustic absorption. In other words when curtains are drawn, there are many visitors or perhaps a window may be open

Low-input, high quality legume hays for north Queensland

Perennial herbaceous legumes grown for hay can improve beef and dairy production in north Queensland through providing affordable high-quality (digestible protein) dry season feed. Eleven Arachis ecotypes (A. pintoi (5), A. glabrata (3), A. paraguariensis (2) and A. kretschmeri (1)), two Stylosanthes guianensis varieties and two commercially recommended Medicago sativa varieties were grown for hay under irrigation using standardised populations in replicated small-plots over two wet seasons (summer) and compared for dry matter production and fodder quality using 8 week cutting cycles. All initially grew well but M. sativa plants were damaged by leaf and stem diseases during wet summer periods reducing leaf and stem growth and resulting in open, weedy stands; the Arachis and Stylosanthes were relatively unaffected and exhibited strong summer-dominant growth throughout the study. There were significant species and varietal differences in biomass production and some A. pintoi, M. sativa and S. guianensis produced over 30 T DM (stem plus leaf above 5 cm cut height) over 19 months. Arachis glabrata also yielded well (16-18 T DM) following a prolonged establishment phase. Feed quality was high for all legumes compared, and overall best in the Arachis spp., with crude protein percentages mostly above 16% and high levels of protein and carbohydrate rumen degradability

Passage and survival of Acaciella angustissima (Mill.) Britton & Rose and Aeschynomene paniculata Willd. ex Vogel seed through the sheep gut

Acaciella angustissima (syn. Acacia angustissima) (white ball acacia) and Aeschynomene paniculata Willd. ex Vogel (pannicle joint vetch), were rejected for release after their identification as potential weeds in pasture evaluation trials. These plants are now targeted for control and, where possible, eradication from old experimental sites across Queensland. It is suspected that domestic livestock, feral and native animals contribute to the movement of these seeds through the ingestion and defecation of viable seeds across the landscape. This aspect was explored by feeding the intact seeds of these two species to sheep in metabolism cages. Sheep faeces were collected each day for 5 days after which time the faeces were sieved and the surviving intact seeds were then collected, counted and germination tests undertaken. The results show that seeds of both species pass through sheep with most seeds being passed after 48 h with a percentage of these seeds being viable. Of the number of seeds fed, 4.25% were recovered for A. angustissima and 1.4% for A. paniculata. Seed recovered from the faeces had 0% and 13% germination for A. angustissima and A. paniculata respectively, but with additional post-digestion hot water scarification germination increased to 75% and 33% for A. angustissima and A. paniculata respectively. This paper discusses these results and the implications for the possible spread of these species across the northern Australian landscape

The effect of microphone wind noise on the amplitude modulation of wind turbine noise and its mitigation

Microphone wind noise can corrupt outdoor recordings even when wind shields are used. When monitoring wind turbine noise, microphone wind noise is almost inevitable because measurements cannot be made in still conditions. The effect of microphone wind noise on two Amplitude Modulation (AM) metrics is quantified in a simulation, showing that even at low wind speeds of 2.5 m/s errors of over 4 dBA can result. As microphone wind noise is intermittent, a wind noise detection algorithm is used to automatically find uncorrupted sections of the recording, and so recover the true AM metrics to within ±2/±0.5 dBA

Stocktake and analysis of legume evaluation for tropical pastures in Australia

There has been a large effort dedicated to the evaluation of a wide variety of sub-tropical and tropical pasture legumes in the past. This large body of information is very valuable for guiding any future legume development activities, yet much of this information was at risk of being lost. This project aimed to collate and store this tropical legume evaluation data and use this and knowledge from past researchers to recommend priority R&D approaches and activities for future pasture legume development. Together with retired pasture researchers, legume evaluation datasets were identified, prioritised, and collated into a database which captured over 180 000 data records collected from 567 sites across northern Australia. Using this large integrated dataset, high power statistical approaches were used to identify legume species which performed well across this large range of evaluation sites. Several species and genera were identified which warrant further investigation and further in-depth analysis of the database in species or genera of interest would be valuable. A gap analysis of commercially proven, underused and prospective legumes was conducted across the key production regions of northern Australia. A range of material was identified which could offer potential improvements in seed production, cold, drought or grazing tolerance compared to the current released varieties