Ian Craig

A simple guide to predicting aircraft spray drift

A sensitivity analysis has been performed on a simple Gaussian Diffusion Model used to predict spray drift deposition from agricultural aircraft at far wake distances. It is intended that the model be used as a training tool to demonstrate clearly the basic effects of windspeed, turbulence intensity, release height, droplet size and uniformity on far downwind spray drift deposition i.e. at distances greater than 50 m. Overlapping the model outputs has also provided a useful benchmark against which experimentally obtained spray drift values may be compared. This information has assisted in the preparation of guidelines regarding required buffer zone distances and the best ways in which aircraft pesticide spray drift can be effectively reduced and managed.

Washoff of Residual Photosystem II Herbicides from Sugar Cane Trash under a Rainfall Simulator.

Herbicides are often applied to crop residues, but their fate has not been well studied. We measured herbicide washoff from sugar cane trash during simulated rainfall, at 1, 8, and 40 days after spraying (DAS), to provide insight into herbicide fate and for use in modeling. Herbicides included are commonly used in the sugar industry, either in Australia or in Brazil. Concentrations of all herbicides and applied Br tracer in washoff declined exponentially over time. The rate of washoff during rainfall declined with increasing DAS. Cumulative washoff as a function of rainfall was similar for most herbicides, although the most soluble herbicides did have more rapid washoff. Some but not all herbicides became more resistant to washoff with increasing DAS. Of the total mass washed off, 80% washed off in the first 30 mm (∼40 min) of rainfall for most herbicides. Little herbicide remained on the trash after rainfall, implying nearly complete washoff.

PESTICIDE SUSTAINABLE MANAGEMENT PRACTICE (SMP) INCLUDING POROUS BIOCHAR/GEOPOLYMER STRUCTURES FOR CONTAMINATED WATER REMEDIATION

As a result of agribusiness in Australia and across the world, water is contaminated with nutrients and pesticides which threaten riverine environments, wetlands, urban drinking water supplies and also marine assets such as the Great Barrier Reef (GBR). Much can be done and sustainable management practices (SMP) can be put into place to reduce water impacts from agriculture. Required investment levels are insignificant compared to the economic advantages to be gained from adopting appropriate SMP across Australian and global agribusiness. SMP technologies need to be targeted at specific pesticides (eg. atrazine, simazine, diruron, ametryn, hexazinone, tebuthiuron, dieldrin, metalochlor, 2,4 D, triclopyr, picloram and bromacil). Surface runoff from agricultural enterprises is conventionally managed by retention lagoons facilitating water reuse on-farm, but these can be breached during heavy storms. Long term deep drainage from fields and seepage from lagoons can also lead to contaminated groundwater. Research, development and testing of appropriate non-leaking/reactive spillways and subsurface geostructures needs to take place across the various agricultural industries. For surface water it is suggested that spillways could be designed with replaceable biochar baffles, and for groundwater, trenches of biochar could form Permeable Reactive Barriers (PRB). The potential for green or brown waste material derived biochar products, which could be readily manufactured from farm refuse and manure, needs to be thoroughly investigated in this regard. The challenge for engineers is to come up with geostructural designs which are efficient, cost effective and which will be taken up and embraced by Australian and world agribusiness.