ROI for NDVI-based side-dressing in corn crops

Queensland Drones has been actively working with growers across a variety of crops since for more than two years to show the benefits of using NDVI (normalised difference vegetation index) mapping to determine the optimal application of fertilisers, pesticides, herbicides and other crop inputs. Although we almost always see some level of crop stress in our NDVI maps, it’s sometimes more challenging to link this to actual crop outcomes this early in the technology hype cycle.

So it was very exciting to learn that Deveron and Veritas, two of the leading proponents of NDVI in the US, have released a case study showing the actual return on investment for a corn crop where side-dressing inputs have been managed using drone-based NDVI mapping!

In case you have not yet caught up with NDVI mapping, it’s a way of measuring the stress in crops by measuring how much near-infrared (NIR) light the crop is reflecting back to the atmosphere, using specially modified NIR camera sensors. Areas of similar stress are mapped into zones which can be converted to SHP files for import into GPS-controlled tractors for precise application of fertilisers and other crop inputs.

NDVI crop stress maps (right) are converted into GPS-enabled crop input maps for controlled application of fertiliser and other inputs

Corn is a great crop to study for NDVI mapping effectiveness, because it responds so well to the timely application of nitrogen just when the crop is ready for a rapid N-uptake. Applying fertiliser in this controlled way is good for the environment because it means less runoff into waterways, but it’s also good for the bottom line because it applies the side-dress only where it’s needed and only in the quantities the crop can actually use at that time.

As they say in the classics, the proof is in the pudding and in this case the pudding is how the controlled application of fertiliser impacted the yield for this crop.

Yield map for corn field side-dressed using NDVI maps

Given the drought conditions in which this crop was being grown and the obvious stress identified in the NDVI mapping above, it is notable that there is little real variation in the yield across the field, other than at the very northern end.

Profit response curves for each management zone based on a corn price of $4.75/bu. and actual nitrogen price of $0.52/lb.

Although the drought conditions were not ideal for this kind of test, it is apparent that there were areas (red curve) where the application rate could have been cut even further as the crop was unable to fully take up the N application. It was also apparent that there were areas (green curve) where even more N could have been used by the crop.

The bottom line was the N was able to be applied at the time when the crop was most ready to use it, and at rates that matched the capacity of different parts of the crop to utilise the nitrogen (and avoid wasting fertiliser on areas that were going to show low productivity in any case due to the drought).

You can download the full report at Deveron. If you would like to find out more about NDVI-based crop management, complete the enquiry form below or give Tony a call on 0439 383202.

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