Unmanned aerial vehicle (UAV) technology is being utilized as part of a three-year trial funded by SAGIT to effectively identify barley grass densities in cereal crops on Upper Eyre Peninsula.
While a poor 2017 season in the region has thrown up challenges, the mapping and subsequent flights to verify results is showing promise.
Amanda Cook, SARDI Research Officer, Minnipa Agricultural Centre, is working with independent contractor Terry Traeger for the delivery of UAV images (normal and normalized difference vegetation index), and Wisdom Data and Mapping’s Scott Gillett, whose company analyses the data.
The project aims to verify the grass weed data captured by aerial images with paddock transects. The ideal would be for three flights a year – before canopy closure, an interim one in late September and a final one while the crop is still green, but as barley grass is turning off.
The process involves assessing weeds in-crop at GPS points along a transect for weed density before grass weed spraying, and also measuring weed density in 30 GPS positions in the paddock to verify the information captured by the UAV flight and analysis.
Mr Gillett says UAVs offer about 20cm accuracy and are particularly suited to areas less than 100 hectares.
With aerial data from points identified as having varying degrees of infestation – and across the whole paddock – he would try different methods of spatially analyzing the imagery.
“The computer can then make comparisons and identify weed status in other areas, which Amanda can ground-truth,” Mr Gillett said.
“I believe UAVs are a good method for getting information back in a few days – and the interim data is promising.”
Mrs Cook said that because of the late start and poor opening rain on Upper EP this year, two of the paddocks on the farms of Bruce Heddle, Minnipa, and Gregor Wilkins, Yaninee, changed rotation from cereal to pasture paddocks.
“The pasture paddocks have still been flown with the UAV to capture the grass weed density and location in the paddock,” she said. “These paddocks will be followed in the 2018 season in cereal crop.
“There are also paddocks in the area with suspected resistance to Group A herbicides as the grass weed patches are circular and spreading (and) this will provide an opportunity to see if data capture and UAV technology can be used to provide an accurate tool for weed-seed monitoring on-farm.”
The project will also assess barley grass weed seed capture by swathing a wheat crop early in a paddock at Minnipa, and the subsequent weed seed capture in chaff dumps after harvest. “We’re looking to see if we can collect more barley grass seed by swathing or cutting the wheat crop earlier than normal harvest time, at between 20% to 40% grain moisture content,” Mrs Cook said.
While harvest weed seed collection works with ryegrass, barley grass drops its seed a lot earlier. “We will continue to evaluate swathing the crop for several more seasons to see if it’s a useful tool to increase the amount of barley grass we can capture into the windrow, and then into the chaff cart.”