Structural and Performance Evaluation of a Pollen-duster, Designed for Date Farms

Pollinating elevated date palms has been a challenging problem for many years. A few types of equipment have been designed and manufactured in the last fifty years, using either low pressure or compressed air to overcome this problem. However traditional pollination is still the most popular method in none-mechanized and small date farms. In the present research, a light portable electrical pollen-duster has been developed and tested. A powerful ducted fan, equipped with a speed controller and a servo tester was made and installed on the top of a 6 -7.7m long carbon fiber boom, to provide a high volume rate of air flow for pollination. A small part of air flow is conducted through a by-pass tube to hit the pollen/pollen-flour blend in the pollen bin and suspend it. The rest of air flow, passing through a venturi, is responsible to provide a relative vacuum at the opening of pollen bin to pull up the suspended pollen and throw it toward the date palm crown. Although plain flour is traditionally used as filler in mechanical pollinators, however, SEM imaging showed that pasta flour particles are bigger than plain flour particles and are closer in size to pollen particles. Also, Repose angle of date pollen was measured as 38º where plain flour and pasta flour showed 44.9º and 40.7º respectively (figures 6 and 7). So, Pasta flour was used instead of plain flour to make a blend.
To provide a low-weight pollen-duster, wires extending from ducted fan to its actuating equipment (battery, servo tester, and speed controller) were selected to be a combination of 2.5mm2 (3 meters) and 1.5mm2 (3 meters) types in the standard boom. This lowered the applied force on the operator’s hand by 33% (Figure 5 and equations 4 and 5).
Evaluation of the pollen-duster has been performed in Khoor town in Isfahan province of Iran. Eighteen trees of Kabkab variety were pollinated in a completely random test with 6 treatments (five mechanical treatments compared with traditional treatment). Mechanical treatments were using 0.5, 1.5 and 2.5g pure pollen and 2 and 6g pollen-flour blend (in 1:3 ratio) in each of the three weekly repetitions. After 8 weeks, in kimri stage, normal, abnormal (non- pollinated), and dropped fruits on some randomly selected strands were counted to determine pollination as well as fruit setting efficiencies. Fruits weight in each treatment was measured on some random fruits in the Tamar stage. A new index; called "pollen consumption index", was introduced to provide a measure of pollen consumption rate in order to prevent redundant pollen consumption which has no sensible effect on the yield.   Calculated pollination and fruit setting efficiencies did not show a significant difference in all treatments, convincing that the traditional method could be replaced by pollen-duster without any yield difference. It offers benefits of lower pollen consumption; more trees pollinated in a day and also safer pollination due to reducing number of trees climbing. It was also shown that a tree could be pollinated properly with 0.5g pollen, so each hectare of date farm (120 trees) needs almost 180g pollen for all three replications, almost 1/4 of Perkins consumption report and 1/3 of Mostaan for three replications. Fruits weights of two pollen-flour treatments were significantly lower than others. As there is not any report available on the effect of the presence of flour or concentration of pollen on date fruits weights, so with the available data no definite reasoning can be made. The developed pollen-duster could be used instead of the traditional date palm pollination method with the same fruit set and lower pollen consumption. The weight of the fruits in pollen-flour treatments `was lower than pure pollen and traditional treatments.