The effect of leaf shape on the deposition of spray droplets in rice

Paddy rice is usually sprayed with different types of conventional hydraulic nozzles and application rates. Spray droplets are more easily captured by the tip of rice leaves; this phenomenon was therefore studied with rice plants in a settling tower so that deposition of droplets occurred under controlled conditions. Further tests were carried out in rice fields by dirferent methods. The deposition rate was generally higher at the leaf tip compared with other parts, whether the leaf was vertical, pointing downwards at an angle of 60 degrees, horizontal or in a normal position. Similar results could be obtained if leaf-like water-sensitive paper strips were used instead of a natural rice leaf. The deposition and distribution pattern found on field rice leaves confirmed these results. Deposits on water-sensitive papers of different widths (2–25 mm) showed fewer droplets as the target width increased.