Recycling efficiency assessment and climate factor–driven dilution modeling of recycled spray overconcentration in tunnel spraying system

• Temperature and RH have a significant effect on the active ingredient concentration, evaporation and recycling rate. • A maximum recycling rate was found of 39.17%. • The active ingredient concentration varied from 4.11% to 20.96%. • The optimum temperature and RH are 20°C and 70%, where no need for dilution. • Evaporation prediction model, E = 5.54 + 2.37×2 – 1.57×3, can be used for the dilution. The recycling system of the tunnel sprayer recovered a significant amount of the sprayed mixture, and usually reused it directly for the spraying. The spray characteristics of the recovered spray mixture are affected by the climatic factors—temperature and RH. Therefore, this study was conducted to analyze how temperature, RH, and their interaction influence the recycling rate, active ingredient concentration, and evaporation. Under laboratory-controlled conditions, a novel tunnel sprayer was developed, and tested for assessment of the recycling rate, active ingredient concentration, and evaporation. Study results showed that climatic factors significantly affect both active ingredient concentration and evaporation, which ranged from 4.11 % to 20.96 % and 2.02 % to 12.16 %, respectively, highlighting the levels of increased concentration, which could have the potential harm to environmental ecology, and degrade soil quality. The maximum recycling rate was recorded at about 39.21 per cent, which provides additional farmer income. The general evaporation prediction equation is E = 5.54 + 2.37×2 – 1.57×3, developed by considering only significantly parameters―temperature (X2) and relative humidity (X3); it can be used to determine the appropriate water quantity to dilute the undesirable recycled concentration. The ideal climatic conditions for the tunnel sprayer operation are a temperature of 20°C and a relative humidity of 70 %, depicting no need for the concentration dilution and if these climatic conditions don’t exist in the field, then the concentration of the recovered spray mixture has to be diluted using the evaporation proposed model before its use.