Assessing Crucial Shaking Parameters in the Mechanical Harvesting of Nut Trees: A Review

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript presents a comprehensive review of the advancements in mechanical harvesting techniques for nut trees, focusing on the crucial parameters affecting the efficiency of such operations. The authors have successfully synthesized a substantial amount of literature on the topic, providing valuable insights into the design and optimization of mechanical harvesters. The review is well-structured, and the information is presented clearly, making it accessible to both researchers and practitioners in the field. Some concerns:

1. The authors have done an excellent job of covering a wide range of studies related to mechanical harvesting. However, it would be beneficial to include more recent studies to ensure that the review reflects the latest advancements in the field.
2. While the manuscript is generally well-written, there are sections where clarity could be improved. For instance, in the discussion of shaking frequency and amplitude, the authors should provide clearer definitions and explanations to avoid ambiguity, particularly for readers who may not be familiar with the technical jargon.
3. The inclusion of figures and tables summarizing key findings from the literature would enhance the readability of the manuscript. Visual aids can help to illustrate complex concepts and data, making it easier for readers to grasp the main points.
4. The review would benefit from a more detailed discussion on the methodologies employed in the studies cited. This would provide readers with a better understanding of the experimental setups and the reliability of the findings.
5. The authors briefly mention the potential for modern computing technology in optimizing shaking parameters. Expanding this section to discuss future research directions and technological innovations would provide a more forward-looking perspective and encourage further investigation in this area.
6. The conclusion effectively summarizes the main findings of the review. However, it could be strengthened by reiterating the practical implications of the research and suggesting specific recommendations for practitioners in the nut harvesting industry.

Overall Evaluation:

The manuscript is a valuable contribution to the field of agricultural engineering and mechanical harvesting. With minor revisions addressing the above comments, it has the potential to be published in the journal. I recommend acceptance after revisions.

Author Response

We sincerely appreciate the thoughtful feedback from the reviewers of our work. We have revised the manuscript based on the comments we have received. Detailed answers addressing the comments are given below.
Note: We have categorized our responses using three distinct colors: Blue for comments from the first reviewer, Green for the second reviewer, and Red for the third reviewer.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The various mechanical harvesting methods mentioned in the paper lack detailed descriptions of specific experimental designs and data collection methods. It is recommended that a detailed description of the experimental design, data collection methods and analysis techniques be added.

A large number of experimental results on vibration frequency, amplitude and duration are provided in the paper, but the analysis of these results is rather superficial. It is recommended that an in-depth discussion of the results be added, especially the mechanisms by which different parameters affect nut removal efficiency and tree damage.

Comments on the Quality of English Language

Minor editing of English language required.

Author Response

We sincerely appreciate the thoughtful feedback from the reviewers of our work. We have revised the manuscript based on the comments we have received. Detailed answers addressing the comments are given in the attached file.
Note: We have categorized our responses using three distinct colors: Blue for comments from the first reviewer, Green for the second reviewer, and Red for the third reviewer.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have carried out an extensive review of scientific articles related to the mechanical harvesting of fruits using vibratory systems (124 citations).

The task undertaken is valuable because it is a subject on which much work has been done since the middle of the last century, so it is not easy to synthesize ideas, for this reason the work deserves to be published.

However, the extent of the information analyzed is such that I believe that many works have not been read thoroughly, and it would be convenient to carry out a deeper reflection on some of the aspects analyzed, since many factors intervene that must be defined a priori with precision so that the conclusions obtained are valid.

In my opinion, the main factors involved are:

-species and variety, for example, vibrating pine trees is not the same as vibrating olive trees

-vegetative state of the plant, for example, vibrating orange trees in winter, when they do not usually present problems of bark stripping, is not the same as vibrating them in spring-summer, when damage to the tree's bark will occur

-size of the tree, a tree with a short trunk (for example 0.5 m) will be vibrated with a trunk vibrator at a very short distance from the ground, which requires using vibrations with very little amplitude (<2 cm) and it will be necessary to increase the frequency, while a tree with a tall trunk (for example 2 m), would allow the use of greater amplitudes (5-15 cm) and lower frequencies.

-Manner of handling the tree, super-intensive trees of small size and high plantation density, should be harvested with continuous crown vibrators, since it would not be efficient to vibrate each trunk. By the way, there is hardly any talk about this type of machine, which is currently the most commonly used for harvesting super-intensive olive, almond and citrus trees.

-Regarding damage, it is necessary to distinguish between damage to the fruit, which in the case of nut trees is usually less important, and damage to the trees. In the latter case, damage can be to the roots, to the contact area between the shaker and the trunk or branches, and also to leaf stripping. This last aspect is very important when very high frequencies are used (>20 Hz, but it depends on the crop).

-It is necessary to define what is meant by 'efficiency', because one thing is the percentage of fruit knocked down, and another thing is economic efficiency, in terms of the time needed to knock them down. For example, branch shakers are said in the article to be inefficient, and indeed they are in terms of the time needed to vibrate a tree compared to trunk shakers, because they need to vibrate several branches, but if what we are referring to is the quantity of detached fruit, it can be as efficient or more than the trunk shaker, it is all a question of vibrating more branches.

In general terms, it is known that the percentage of detachment increases with the frequency, the amplitude of the vibration and the vibration time. The point of attachment of the shaker to the tree is also very important. Summary tables have been presented in an attempt to provide the most important parameters obtained from the various articles consulted. It is a good task, but it is necessary to complete it, at least when talking about trunk shakers, for each case information should have been collected on frequency, amplitude, duration, height of the attachment point and approximate size of the tree.

It is true that many of the works analyzed do not provide all this information, which already indicates that the conclusions reached in them are incomplete.

Below I highlight some aspects that have caught my attention:

-line 155, it says that in California the frequency and amplitude used to collect pistachios are 20-30 Hz and 50-60 mm. In Europe similar frequencies are usually used, but the amplitudes are usually around half that.

-In lines 190-194, citing Liu et al. [75], it is said that walnut trees were vibrated at 10-30 Hz, but that the fruits vibrated at 4-15%, with an attenuation of 50%. I do not believe it, the amplitude of the vibration is attenuated or accentuated, not the frequency of the wave, therefore it must be an error in the original article.

-In lines 320-324 the work of Polat et al. is cited [87] where it is concluded that the combination of 40 Hz and 20 mm amplitude was the most efficient of all those tested. Of course, they were the highest frequency and amplitude of this test, and thedetachment increases with both factors, but the balance between detachment and damage must be analyzed; at 40 Hz, the leaf stripping was surely excessive. On the other hand, this analysis is incomplete, since it would be necessary to know the duration of the vibration because 1 s at 40 Hz means docuble cicles and stronger than 1 s at 20 Hz, i.e.

-In lines 335-336, a force amplitude of 3000 N is mentioned; the way of measuring the vibration is being changed; in the rest of the cases, the amplitude refers to the displacements. On the other hand, the force necessary to move the branch or trunk will depend on the power of the vibrator and the resistance of the plant.

-Lines 402-404, the potential of intelligent machines that can adjust the vibration parameters to the size of the plant and other factors is discussed. I think this is very hypothetical, because for example, the frequency can be varied within certain limits with the speed of the motors, but regulating the amplitude is not easy. The easiest factor to control would be the duration of the vibration.

-Speaking of the duration of the vibration, throughout the article I see somewhat strange results. Experience tells me that in fruits with very short peduncles, such as almonds, stone fruits and similar, a very short vibration of the order of 2-3 s is sufficient to detach almost all the fruits (in line 540 it speaks of 5-10 s). In the case of fruits with long and flexible peduncles, such as olives or citrus fruits, the vibration is poorly transmitted along these and longer times are necessary, but normally they do not exceed 10 s.

-Section 3.2. Canopy Shaker System, is very poor, as it only refers to a system with poles that are introduced into the vegetation, when it is possibly the most widely used system in the harvesting of citrus for industry (Oxbo) and we must also consider the systems that hit the canopy laterally, such as those based on grape harvesters for olive, almond and super-intensive citrus trees.

-On line 477 it says '4-12 inches', please express it in SI units.

-Finally, section 5 is so vague that it provides little.

Author Response

We sincerely appreciate the thoughtful feedback from the reviewers of our work. We have revised the manuscript based on the comments we have received. Detailed answers addressing the comments are given in the attached file.
Note: We have categorized our responses using three distinct colors: Blue for comments from the first reviewer, Green for the second reviewer, and Red for the third reviewer.

Author Response File: Author Response.pdf