Hill country farms cover a wide range of varying land slopes, aspects, soil properties and altitudes, all of which influence the potential productivity of pastures. Even within a single paddock, significant differences in soil fertility occur, translating to variability in fertiliser responsiveness. Capturing soil fertility through remote sensing on a scale previously unthinkable offers the opportunity to transform nutrient use and productivity for hill country farms.

AirScan is the result of Ravensdown’s Pioneering to Precision Primary Growth Partnership with the Ministry for Primary Industries. Its objective? To transform precision nutrient application: the right nutrient, at the right rate, in the right place, at the right time. Entering its final year of a seven year programme, the aim of maximising the return on every fertiliser dollar spent is within our grasp.

We are now confident that there is a relationship between the remote sensing imagery and the plant nutrients nitrogen (N), phosphorus (P) and soil Olsen P. Additional nutrients are still being investigated but some challenges remain, with it being critical that pastures are in rapid growth and a vegetative state to obtain a good correlation between plant chemistry and soil fertility. However, Ravensdown is now concentrating on ensuring that the technology is suitable to be offered as a commercial service.

The high-end sensor involved is extraordinary in its ability to conduct the equivalent of 10,000 soil tests per hectare, when flown at a 600m altitude. It does this by measuring light signatures on the ground to a resolution of 1m2. When you extend this to its ability to cover large areas in a short space of time, with a survey rate of 1,000 ha an hour, this becomes the equivalent of conducting 10 million soil tests an hour. At this scale fertiliser plans are no longer restricted to paddocks as fence lines become irrelevant.

Crucially, Ravensdown has also developed tools to integrate the high- resolution soil fertility information with a farm’s physical information to estimate current and potential pasture production. This allows a comprehensive cost-benefit analysis to determine the financial benefits of maintaining or increasing soil fertility, or withholding fertiliser spatially across the farm.

The last piece of the puzzle is Ravensdown’s continued development in improving capability in precision aerial applications. In the last six years, automated flow control (IntellispreadTM) has been introduced into four of our commercially operated topdressing aircraft.

Soil testing from the sky is a lot closer to reality, and when coupled with automated flow control in topdressing aircraft it is a game-changer for increasing the precision of variable rate fertiliser strategies – thereby maximising the return on every fertiliser dollar spent.