Spray deposition and losses in potato as a function of air-assistance and sprayer boom angle

Fábio Scudeler,Carlos Gilberto Raetano

doi:10.1590/s0103-90162006000600001

Abstract

Within the Brazilian agricultural scene, the potato crop plays a significant economic role. Modern equipment and the development of improved chemical product application techniques contribute toward the constant search for improved revenue from the potato as a crop. Field experiments were carried out in a random block design of a potato crop of the "Ágata" variety. The aim was to evaluate the effect of air assistance combined to different angles of spray application on the chemical deposition on the potato plant, as well as to assess spray losses to the soil. For this a sprayer with and without boom air assistance was used in the experiments. Boom angles of 0º, +30º and -30º were directed to a vertical position as well as forward and backward movements. The trial plants were sprayed at a volume rate of 400 L ha-1 using JA-4 hollow cone nozzles at 633 kPa and copper oxychloride as a tracer for the deposit evaluation. Trace deposits on both surfaces of leaflets were removed by washing with destilled water and were quantified by atomic absorption spectrophotometry. Spray losses were measured by placing plastic measuring collectors between rows. The deposit levels at different positions in the plant were analyzed by the Hotelling T² statistical test. Larger deposits were detected at both upper and lower positions of the plant when the spray boom was positioned at 0º and +30º in the presence of air assistance. The presence of air, in addition to the increasing spray deposits in the lower parts of the plant, helped to create greater distribution uniformity. Spray loss was below 4%.

Highlights

To achieve an effective control of potato diseases and to reduce production costs, the techniques and equipment for the application of phytosanitary products must be improved, which in turn enhances spray distribution and placement of the phytosanitary product on the biological target
Occurrence of greater deposits on the lower position of potato plants by using spray boom angled at 30° in the presence or absence of air assistance and at 0° with air assistance was due to spray dynamics during the movement of the equipment
An adverse effect was obtained when the spray boom was oriented against sprayer movement (-30°), because of the maintenance of smaller droplets longer in suspension and increasing the spray losses

Summary

Introduction

To achieve an effective control of potato diseases and to reduce production costs, the techniques and equipment for the application of phytosanitary products must be improved, which in turn enhances spray distribution and placement of the phytosanitary product on the biological target. Scudeler & Raetano the fungicide application to a field crop, sprayers have been equipped with air-assistance booms, which allow a directed spray mix flow avoiding drift losses (Cooke et al, 1990; Bauer & Raetano, 2000) They provide better product distribution and deposition on the abaxial surface of leaves of the lower parts of the plant (Leonard et al, 2000; Panneton et al, 2000; Venegas, 2002; Scudeler & Raetano, 2004), increasing the penetration of droplets into the crop canopy (Matthews, 2000), as well as reducing spray deposit variability (Venegas et al, 2003). In some cases, deposition on plants has been higher than 64% of the total applied (Pergher & Gubiani, 1995)

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