The vibration behaviour of hedgerow olive trees in response to mechanical harvesting with straddle harvester

doi:10.1016/j.biosystemseng.2019.06.009

Biosystems Engineering

Volume 184, August 2019, Pages 81-89

https://doi.org/10.1016/j.biosystemseng.2019.06.009 Get rights and content

Highlights

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Vibration transmission from harvester to hedgerow is close to 60%.
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The main direction of vibration is transverse to the harvester's displacement.
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For 62% of the tree vibration time it is in direct contact with the harvester rods.
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Acceleration values in the canopy increase with tree height.
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There are two canopy zones according to height with different vibration behaviour.

Understanding tree behaviour under mechanical harvesting is very important for orchard management and machine design. The objective of this work is to determine the dynamic response of trees, in a hedgerow arrangement, to a straddle harvester with canopy shaker. Forty-four points were measured in random trees at different heights above the ground. The main vibration parameters in the time and frequency domains were analysed. The transmission range of acceleration between machine rods and trees was 58%, vibrating at a similar frequency of 7.8 Hz. The acceleration values registered in the main direction of rod movement were higher than both in the direction of the hedgerow and vertically. The rods of the harvester are in direct contact with the tree canopy 62% of the tree's vibration time. The resultant acceleration values show a temporal distribution similar to a Gaussian curve but distribution throughout the total vibration time shows that only 49.2% of these values are lower than 50 m s⁻² and 93.3% are lower than 300 m s⁻². The analysis of vibration time in a range gives more information about the impact of shaking. The tree responded differently at different canopy heights in terms of acceleration RMS and peaks, identifying two zones.

Graphical abstract

Introduction

Olive is a crop with strong international importance, and one which is experiencing great development. The traditional plantation layouts of the Mediterranean basin (fewer than 200 trees ha⁻¹) are being changed for ones with smaller tree-spacing such as intensive (200–400 trees ha⁻¹), high-density (400–700 trees ha⁻¹) and super-high-density (over 1500 trees ha⁻¹). These new orchard designs are being adopted all over the world where olive can be grown. The orchard typology choice depends on different factors: ecological conditions, orchard size, manpower availability, economic investment, etc. (Tous, Romero, Hermoso, Msallem, & Larbi, 2014). Each typology has a different tree architecture and so requires different tree training and management.

The design of tree architecture may influence yield and fruit characteristics (Lavee, Haskal, & Avidan, 2012) and is closely related with the harvesting technology to be applied, and thus with crop profitability (Bernardi et al., 2018). The relationship between tree architecture and harvesting technology is, on the one hand, conditioned by the available mechanical harvesting systems, which perform different vibration patterns (Sola-Guirado et al., 2014). On the other hand, tree behaviour under excitation, such as a vibration, is related to the spatial and temporal arrangements of its trunk, branches and shoots. The growth and development of a tree can be controlled by physical parameters such as tree spacing, canopy growth or branching, and by physiological parameters such as leaf density and photosynthetically active radiation (Cherbiy-Hoffmann, Searles, Hall, & Rousseaux, 2012).

The super-high-density olive orchard system is the most suitable for implementing a high degree of mechanisation, which makes it highly attractive for farmers and investors. Its main advantage is fast harvesting, which is performed by straddle harvesters with a canopy shaker, a technology imported from vineyard harvesting. However, years ago, orchards were not adapted to allow continuous harvesting with canopy shakers and were composed of isolated trees suitable for trunk shakers or manual beating. Orchard designs have had to be converted by putting the trees together to create a hedgerow in order to use straddle harvester technology. Tree structure and fruiting must suit the harvesters, but the harvesters must also match the hedgerow features (Connor, Gómez-del-Campo, Rousseaux, & Searles, 2014.; Tombesi & Farinelli, 2017) This work focuses on machine-tree dynamic interaction and their behaviour under mechanical shaking.

Straddle harvesters with a canopy shaker apply a particular vibration by means of the alternate movement of two opposite walls of rods that compress the tree canopy on both sides, while moving forward to the adjacent tree at a uniform ground speed. Several authors have studied canopy shaker regulation on lateral harvesters for other crops such as citrus (Gupta et al., 2016, Pu et al., 2018). There are also results for the vibration pattern of canopy shakers on straddle harvesters in other crops such as grapes (Pezzi & Caprara, 2009). The influence of straddle harvesters with canopy shakers in olive orchards has been studied for performance (Ravetti & Robb, 2010), oil quality (Farinelli & Tombesi, 2015), and damage caused to the fruit (Morales-Sillero, Rallo, Jiménez, Casanova, & Suárez, 2014) or the trees (Pérez-Ruiz et al., 2018).

Olive behaviour under vibration in mechanical harvesting has been studied mainly for the application of trunk shakers on isolated trees (Castro-García et al., 2008, Hoshyarmanesh et al., 2017). In order to gain a deeper understanding of the mechanical harvesting of this modern orchard type, it is necessary to study the two component machine (straddle harvester with canopy shaker) and the tree (olive in hedgerow configuration) (Tombesi & Farinelli, 2014). Optimisation of harvesting will be achieved by maximising fruit detachment, minimising tree damage, and minimising the time spent on the operation. The way to achieve these is to properly adjust the machine parameters and to train trees, which requires an understanding of what happens in the tree structure during harvesting. The objective of this work is to determine the dynamic response of the trees with narrow continuous canopies harvested using a straddle harvester with canopy shaker. The results and the methodology employed may be used in the harvesting of other crops with similar machines and provide suitable advice to enhance mechanical harvesting.

Section snippets

Material and methods

Tests were conducted in an irrigated, super-high-density olive orchard (830 trees ha⁻¹) of the ‘Arbequina’ cultivar, located in Cordoba (lat: 37° 56′ 04.8″ N, long: 4° 43′ 00.90″ W), southern Spain. Trees were over 10 years old, in good physiological and health conditions, with a canopy volume of 5.32 ± 1.31 m³ tree⁻¹ and a tree spacing of 2.00 m. Tree pruning had been adapted to over-the-row harvesting systems with a hedgerow diameter of 1.11 m and a canopy height between 0.57 m and 2.95 m

Results and discussion

The lowest canopy branches were shaken because of the configuration of the machine height, but also the top branches that were shaken into the tunnel because of their elasticity. The branches vibrated with a frequency of 7.8 ± 0.1 Hz (mean ± sd), very close to the harvester rod shaking frequency, and concurring with the values reported by other authors for similar machines (Pezzi & Caprara, 2009). The frequency at which the trees are excited to detach fruit varies according the harvesting

Conclusions

The data reported provide a valuable quantitative study of the vibratory phenomena that occur during the mechanical harvesting of olive trees in a hedgerow arrangement with a straddle harvester.

There is a low transmission rate of acceleration between rods and branches that may suggest performing an analysis of the phenomenon as a non-forced or discontinuous vibration. The acceleration range above 18 m s⁻² may be a good criterion to calculate the vibration time in which tree vibrates due to

Acknowledgments

The authors strongly acknowledge the support through the pre-commercial public procurement Innolivar of the Spanish Ministry of Science, Innovation and Universities and the Interprofessional Organisation of Olive Oil and Table Olive. The authors also appreciate the collaboration of the olive farm of the University of Cordoba.

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Research PaperThe vibration behaviour of hedgerow olive trees in response to mechanical harvesting with straddle harvester

Highlights

Graphical abstract

Introduction

Section snippets

Material and methods

Results and discussion

Conclusions

Acknowledgments

Science of the Total Environment

Scientia Horticulturae

Biosystems Engineering

Scientia Horticulturae

Scientia Horticulturae

Scientia Horticulturae

Computers and Electronics in Agriculture

Scientia Horticulturae

Biosystems Engineering

Journal of Food Engineering

Journal of Food Engineering

Biosystems Engineering

Biosystems Engineering

Scientia Horticulturae

Quality of mechanized coffee harvesting in circular planting system

Ciência Rural

Dynamic analysis of olive trees in intensive orchards under forced vibration

Trees – Structure and Function

The fruit detachment force/fruit weight ratio can be used to predict the harvesting yield and the efficiency of trunk shakers on mechanical olive harvesting

Acta Horticulturae

Transformation of an ancient crop: Preparing California “manzanillo” table olives for mechanical harvesting

HortTechnology

Research Paper
The vibration behaviour of hedgerow olive trees in response to mechanical harvesting with straddle harvester