Agricultural drone surveys like those provided by Qld Drone Photography have been embraced by broadacre growers because of the massive advantages of aerial crop scouting over ground-based crop scouting in large fields like cotton. But are they really effective?
Although we see results for ourselves in the outcomes of surveys we perform for our customers, we also look to external research to validate what we’re seeing.
In June 2014, Cotton Grower magazine reported on the increasing buzz about NDVI surveys using UAVs in the cotton industry in the USA. The magazine saw this new technology as a game changer for growers and consultants in the cotton industry and one of the top priorities for the FAA (the US equivalent of CASA in Australia) for regulatory reform. In fact, the FAA had taken the bold step of joining in with a research program across six test sites in North Dakota to prove the value of UAVs (drones) in checking soil quality and crop health for cotton growers.
Dr Ed Barnes, senior director of agricultural and environmental research for Cotton Incorporated, has identified drone technology as a “game changer” for agriculture generally, and for cotton in particular.
“In cotton, we learned that imagery can definitely help us do a better job of identifying parts of a field to help us better manage plant growth regulators, defoliants and other inputs,” Dr Barnes explains. “All of these things will still be on the table with UAVs. With satellites and airplanes, we were happy if we got image sizes that were three feet by three feet. The thing that’s interesting about UAVs is that they can provide much higher resolution than we’re used to.”
That’s something of an understatement when the UAV survey industry is already producing image sizes down to around a foot and improving every year.
Dr Barnes can foresee a time when agronomists or crop consultants, and perhaps even growers themselves, can use coarse images from satellites to identify areas of variability in a crop and then use finer UAV imagery to get a closer look and help identify both cause and treatments.
“This could be a very valuable tool for consultants to expand what they can offer to their clients.”
Cotton Farming magazine, in its August 2015 home page feature, identifies the “game changer” for UAV use in the cotton industry as being tied to the falling cost of variable-rate spreaders and the growth of GPS-enabled precision agriculture features on new farm equipment.
“Unmanned Aerial Vehicle (UAV) projects have started, and we found that the Normalized Difference Vegetation Index (NDVI) can pick up nitrogen and potash deficiency very well but can’t tell the difference between the two at this point. Also, right now there is a serious issue of processing and interpreting the data from the UAV fast enough to make timely in-season adjustments that will put money in the producer’s pocket.”
Timing is a significant issue for cotton growers who often need to act on the data provided by UAV field surveys quickly for maximum effect. That’s why Qld Drone Photography uses desktop-based analysis systems like Ag Leader SMS Advanced to interpret NIR survey results and develop variable rate prescriptions usually within 24 hours of flying. Cloud-based analysis systems just cannot provide this kind of turnaround yet, especially in Australia where rural internet is desperately slow.
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NDVI imaging case studies from the cotton industry
The image above is an NDVI map of a cotton trial plot when the plants were just 20cm high. This image shows considerable variability in the crop growth that will produce critical differences in the outcomes for harvest if left untreated. The north field is obviously performing much worse than the south field and there is significant variation within sectors of the field as well.
This image shows an 88 hectare cotton crop where the grower firmly believed there were no problems in the crop at all based on his visual scouting, but decided to have the field surveyed anyway just to confirm his thinking. The NDVI map at the top was taken in January and shows significant areas of crop stress which his agronomist subsequently decided needed treatment. The second NDVI map at the bottom was taken three weeks after the treatment was applied and shows a huge difference in crop health.
This image is an NDVI survey of a cotton crop after the application of pre-harvest defoliant. Because all the leaf matter in the crop should now be dead, the image should be almost entirely black. The yellow areas are still reflecting significant amounts of infrared light, which means they are still relatively healthy and the defoliant has not worked as it should. If the crop was harvested at this point it would have been seriously contaminated.
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The cotton survey calendar for Queensland
There are a number of key points in the cotton growing calendar where UAV crop surveys can have major benefits for reducing crop inputs and increasing yields.
- October – After irrigating fields for new crops, check how well moisture is being retained by each section of your fields which may provide an indicator of forward crop yield.
- November – As the crop reaches 8-10 cm average height, check for consistency in row heights as an indicator of opportunities to strategically replant. Identify emerging weed and insect problems to minimise use of insecticides and herbicides.
- December – As the cotton squares turn into flowers, check the uniformity of crop growth and the stress across different parts of the crop to inform accurate timing of first crop irrigation and variable rate application of late fertilisers including foliars.
- January – As the crop is now at full growth and bolls are developing, check again for consistency in crop growth and identify areas of crop stress to inform additional irrigation, fertiliser, growth regulator and foliar applications.
- March – After you apply defoliants to the crop, check to see if the defoliant has consistently removed the leaves across the entire crop or if some re-application is required to avoid contamination of the harvest before picking.
Qld Drone Photography offers a special package for cotton growers with five flights per growing season at a cost of just $20 per hectare. This is an all-inclusive cost covering our travel time, on-farm time, off-farm processing and analysis and provision of NDVI image maps, GeoTIFF images for in-field navigation to problem areas and variable rate prescription maps for your geo-enabled farm equipment.
Use the enquiry form below to book a free 20 hectare trial survey on your farm or phone Tony on 0439 383202 to discuss your particular needs.