Weeds in crop are expensive. They are expensive to manage, they can impact yield and contaminate your seed when it comes time to sell it.

Recently we took on a job that required us to develop an Artificial Intelligence (AI) solution to identify Caldwell’s Club-rush (Bolboschoenus caldwellii) within a rice crop.

Identifying the problem is, of course, only half the problem. We were also asked to integrate our detections into spray drones, and selectively spray out the weeds.

Here’s what happened…

Initial Mapping
The area was first mapped using an RTK drone. Highly accurate data is required so that the spray drone will be spraying the same area that is prescribed. An appropriate GSD (Ground Sample Distance) was selected that would make the weeds visible in the imagery.

Weed Detection
Weeds were then run through a Green-on-Green AI to detect the weeds. This process was remotely supported by the expert eye of the client who was attuned to small differences between the rice and weed species. A total area of less than 1 hectare spread across the paddock was identified as weeds. We added a bufferzone to each detection which increased the overall spray area to around 4 hectares

While one hectare of weeds doesn’t sound like much, if left untreated it will rapidly propagate across the paddock.

Below are some examples of before and after the weed detection was completed. The weeds are indicated with green with the spray area being in red.

The heat-map then shows the distribution of weeds across the area.

This data was then uploaded into spray drones with the chemical applied to the weeds.

– Spray Drift: The client places tomato plants around the paddock which are normally impacted by spray drift from planes as a ‘canary in the coal mine’ for spray drift. These plants normally get wiped out when spray planes are used. No tomato plants were harmed from our activity.
– Cost: A reduction of approximately 95% of chemical use was achieved. See below for cost break-down
– Plant Growth: The spray used to treat the weeds has a negative physiological impact on the rice slowing its growth. Spraying only 5% of the crop meant that the other 95% was not impacted by our operations.

COST SAVING: $21.85 / HA

Total Area: 141.3 Ha
Prescribed Spray Area: 3.9 Ha
Actual Spray Area: 4.3 Ha
Paddock Sprayed: 3%
Chemical Used: 4L
Chemical Saved: 87L
Alternate Cost: $7,488
Cost Saving: $3,088
Drone Spray Drift: 5m

Spray drones are then sent out to spray the area.

Spray drones ready to fly

Just some more examples of the weeds