Further studies on electrostatic date pollination - From the laboratory bench to field unit performance test

Artificial pollination of date (Phoenix dactylifera L.) blossoms is a common means of improving yield and quality. Date growers prefer the use of precise techniques that ensure minimal pollen consumption but require very large amounts of manual labor, however, they often use inaccurate aiming techniques to maintain their application schedule. An electrostatic field applicator was developed in the present work to reduce manual labor and pollen consumption in artificial date pollination. Labor saving was achieved by moving the system continuously, which requires a 2.5-m gap between the unit outlet and the target, in order to avoid collisions with branches. Such a gap is in contrast with efficient electrostatic applications of dry matter since it dilutes the pollen cloud and reduces the space charge. A need to increase the velocity of the pollen-carrying air stream to overcome the prevailing wind also reduces the space charge. Therefore, laboratory tests to define favorable parameters were essential to define the specific design and construction of an efficient unit. Based on the laboratory findings, an accurate-aiming electrostatic field applicator was designed, constructed, and mounted on a mobile elevated platform for use in date orchards. Tests with the field unit showed that it enabled savings of up to 90% and 70% in pollen consumption and labor use, respectively, compared with the commonly used units, while maintaining the high fruit set provided by the commercial devices. Electrostatic charging enabled reduction of pollen consumption to 0.125 g per tree in a single application. By applying excess pollen and reducing fruit set, the new system can save additional labor in the thinning operations.