Multiple Metal Cations as Spray Deposit Tracers and Evaluation of the AGDISP Ground Boom Spray Drift Model

The determination of spray drift by agrichemicals in field applications is laborious and expensive. Dyes have been used as tracers to reduce workloads and costs, but these methods have technical drawbacks. Metal cations have also been used as tracers and this method is promising, especially if a number of distinct cations from consecutive spray applications can be collected cumulatively by the same collectors. This study evaluated the use of various water soluble metal cation salts and plastic tape as a cost-effective collector for spray drift deposits. Measured deposit values were compared with calculated outputs from the AGDISP ground boom spray drift model. The comparisons showed that AGDISP over estimated downwind deposition and under estimated deposition within the last swathe in the spray block. Increasing boom height above the canopy improved within spray block deposition estimates. Varying wind direction had negligible effect; increasing relative humidity gave greater deposition closer to the spray block. These trends are discussed, together with the pros and cons of the metal cation and plastic tape collector system.