Hydraulic-based fixed spray delivery system: Homogeneity distribution among emitters and internal cleaning performances evaluation

Fixed spray systems, an alternative to conventional pesticide application equipment, are under investigation in perennial fruit crops for improving spray applications. A prototype of a hydraulic fixed delivery spray system (31 m length) was evaluated for its suitability to be adopted as crop protection technology. In this research, two emitter densities selected from previous studies were used. Field trials were conducted to evaluate the performances of the system for spray mixture delivery, and to this extent, homogeneity distribution and cleaning performances were tested. Results showed that the emitter nearest to the injection point will deliver, the spray mixture first and water second, sooner than those further down the line. This delivery delay balanced the amount of spray mixture delivered by the fixed spray system along the line. Thus, the system delivered a similar amount (CV = 6.91%) of mixture from every sampled location in both emitter densities tested. Cleaning the line with water reduced the residue concentration by a factor greater than 300 in both emitter densities. In addition, the optimal time for cleaning that also reduced the water volume was identified as 2:30 and 4:30 min for high and low emitter densities, respectively. Linear regression models were built to estimate water volume consumption and cleaning step timing according to the fixed spray system's flow rate. In conclusion, emitter flow rate, emitter number, and spray mixture volume injected resulted the three key factors affecting dose applied, homogeneity of distribution among emitters, and cleaning performance.