Controlled traffic comes under the spotlight
The Queensland Department of Primary Industries has three long-term farmer collaborators with all or part of their properties under controlled traffic — areas varying from 240 to 2,400 hectares — and three newer ones in earlier stages of controlled traffic development.
According to principal soil scientist Don Yule, National Landcare Program grants have allowed the recent employment of Wayne Chapman as a development and extension officer for controlled traffic in Central Queensland, where 600 km separate the most far-flung collaborators' farms.
Although the ongoing drought had slowed progress, Dr Yule said, enough had been done for one collaborator, Lyall Swaffer, to report easier and more efficient fallow management with reduced tractor operating costs in his controlled traffic block, and for the largest collaborator, Rod Birch, of Kilcummin, to gain a planting opportunity that would only have been available with innovative approaches under controlled traffic.
A major advantage of controlled traffic had been the ease and efficiency of herbicide and insecticide spray operations.
The main concerns of collaborators were accurate steering, clearly marking wheel tracks for controlled traffic, and the problem of controlling weeds in them, but a solution seemed likely to come from machinery adaptation.
These could be some of the controlled traffic problems likely to be solved by the computerised tractor-steering system being developed by a team under Professor John Billingsley at the University of Southern Queensland's National Centre for Agricultural Engineering in Toowoomba.
Dr Yule said another significant step in the development of machinery that would exploit controlled traffic's potential was the manufacture of highperformance implements by Connor Shea Napier, working with Dr Tullberg and Toowoomba QDPI engineer Peter Walsh.
Controlled traffic is only one aspect of wide-ranging research into soil problems in cropping lands in Central Queensland.
Effects of compaction
Dr Yule said the extensive soil monitoring and measurement program that was an essential part of the project had shown compaction to have had a number of bad effects on soil properties, such as bulk density, porosity, pore continuity, structure, strength, shrinkage and water infiltration. These conditions had mainly affected early crop growth.
Growers support the research through the GRDC, but funding comes also from the federally funded Land and Water Resources Research and Development Corporation (LWRRDC), the National Landcare Program (NLP) and the Cooperative Centre for Sustainable Cotton Production.
With the backing of LWRRDC and GRDC, research into compaction control and soil repair is into its third year at QDPI Biloela and Emerald research stations.
Soils at the stations are generally representative of the main cropping soils of the northern grains region. Emerald has the heavy, cracking basaltic clays and Biloela the soils of mixed mineral origin common to much of the brigalow country.
Not surprisingly, drought has affected the research program, and Dr Yule admits some of the results have been unexpected.
Dr Yule said while results in 1994 showed significant differences in crop establishment, and in dry matter at anthesis, there were no significant differences in grain yield. "Overall the data indicated reduced growth in the more compacted treatments — traditional, extreme and zero — and similar, but also non-significant responses were measured in 1993," he said.
"Fertiliser significantly reduced grain yield, irrigation increased it, but there were no significant interactions among compaction, irrigation and fertiliser treatments. The fertiliser response and lack of interactions were unexpected.
"We believe the unexpected results are more a reflection of the seasonal conditions experienced by the trial so far, and that they will be accounted for as our work continues."
Contact: Dr Don Yule 079 360 287