Spraying performance of lever-operated and motorised knapsack sprayers, and motorised mistblower on rice crop

M. Md. Jusoh

Abstract

The physical spray parameters of three rice crop-spraying techniques using lever-operated and motorised knapsack sprayers, and motorised mistblower in combination with various nozzles were determined. Results showed that motorised knapsack sprayer fitted with a 5 nozzle boom gave the highest application volume of 284 L/ha as well as the best penetration and coverage of spray droplets. However, it was the worst in terms of contamination of spray droplets on operators. The lowest possible application volume (0.06 L/ha) was achieved with the motorised mistblower fitted with an ultra-low volume nozzle. Such mistblower gave the highest work rate of 6.96 ha/man-day with 100% spraying efficiency when operated at full throttle, restrictor number 3 and a walking speed of 28 m/min. Regardless of sprayer-nozzle combinations, contamination was highest on the right thigh and right hand. The no-swing spray technique gave better coverage as well as penetration, and reduced spray contamination by 60%. Although swinging the lance left and right especially at 160° increased the work rate by 50%, it reduced spray efficiency and increased contamination. The mistblower fitted with either a standard nozzle or a wideangle diffuser nozzle achieved the widest effective swath of up to 10 m of horizontal throw. The most effective walking speed (in terms of having very good coverage and work rate) when operating a mistblower was 36 m/min. At a spray volume of 143 L/ha, the mistblower resulted in significantly better coverage of the upper parts of rice plants. Thus correspondingly, it resulted in better reduction of the green leafhopper population than the lowest application volume of 27 L/ha. No significant difference in terms of spray droplet coverage of the lower part of rice plants was recorded when spray volumes of 27–143 L/ha was used. Hence, there was no significant reduction in the brown planthopper populations.

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