Laboratory Device to Assess the Effect of Mechanical Thinning of Flower Buds, Flowers and Fruitlets Related to Fruitlet Developing Stage

Romano Romano,Ortiz Ortiz,Balasch Balasch,Torregrosa Torregrosa

doi:10.3390/agronomy9110668

Romano Romano, Ortiz Ortiz + Show 2 more

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https://doi.org/10.3390/agronomy9110668

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Abstract

Mandarin thinning is done by hand, increasing labor costs and raising total cropproduction costs. Mechanical thinning has been tested in peaches and other fruits. To achieve themaximum efficiency thinning has to be applied at a specific stage of vegetative development. In thisresearch study, the mechanical thinning of ‘Clemenrubi’ mandarin branches during the differentfruit development stages have been assessed using a vibratory laboratory device (amplitudes 0.015and 0.030 m and frequencies 34.8 and 37.8 Hz). Branches with flower buds, flowers, small greenfruits, and medium green fruits were tested for 12 weeks, in two different seasons. It was possibleto mechanically detach flower buds, flowers, and green fruits using different combinations ofamplitudes and frequencies. Removal percentage decreased when increasing retention tractionforce, according to a logarithmic regression model. A significant increment in equatorial diameterand retention traction force was registered when the fruit setting was finishing, while mass had asimilar development with a week delay. During fruit setting (weeks 5, 6, and 7) removal percentagewas higher, while the retention force was very low. The first weeks just after the natural thinningcould be considered the adequate time for a mechanical thinning operation.

Highlights

Fruit thinning is the removal of certain flowers or fruitlets in order to improve fruit yield and quality and return bloom for the following year [1]
The final size of citrus fruits depends on the degree of competition among them, apart from other factors
Mandarin hand thinning is usually done in some regions, like Valencia in Spain and the South Island in Japan

Summary

Introduction

Fruit thinning is the removal of certain flowers or fruitlets in order to improve fruit yield and quality and return bloom for the following year [1]. The final size of citrus fruits depends on the degree of competition among them, apart from other factors. Larger numbers of flowers and fruits increase competition that reduces total growth and the final size of the fruits [2]. There are three methods for thinning or crop load management: Hand, mechanical, and chemical. Hand thinning is not often applied as a commercial, cultural practice in citriculture due to the high cost [3]. Mandarin hand thinning is usually done in some regions, like Valencia in Spain and the South Island in Japan

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