Effect of Fertigation on the Physicochemical Quality and Antioxidant System of ‘Fino’ Lemons during Postharvest Storage

Round 1

Reviewer 1 Report

The paper is not a novelty. Several research in the last 20 years have already demonstrated how high levels of fertilization, especially nitrogen, do not determine high production and fruit quality. Indeed, quite the opposite has been demonstrated.

In the introduction it is necessary to add how important good agricultural practices related to fertigation and nutrition are from the point of view of an agroecological approach.

In the materials and methods I would add bibliography relating to citrus because so much has been done in Europe and in the Asian areas where citrus are cultivated.

The use of best agricultural practices have demostrate to be the best methods to improve and sustain agricultural production, soil health, and the environment. Recent advances on effective need-based nutrient management, and the concept of precision agriculture, can also be explored to improve soil health and agricultural sustainability. For this reason and to accept the paper, in the part of the results must be emphasize how good agricultural practices, in addition to an advantage for the environment, lead to high quality fruit which is thus advantageous for human health.

Author Response

REVIEWER 1

 

Dear reviewer, we are very grateful for your useful comments which have helped to improve our original manuscript. Please find below a detailed list of your comments and suggestions and the answers and modifications performed in the revised manuscript according to your suggestions. The new information added to the revised manuscript has been highlighted in green ink and the English grammar has been revised according to your suggestion. Besides, English changes have been done using red ink.

Comment 1. The paper is not a novelty. Several research in the last 20 years have already demonstrated how high levels of fertilization, especially nitrogen, do not determine high production and fruit quality. Indeed, quite the opposite has been demonstrated.

In lemon fruit production, nitrogen (N) is normally increased drastically during the fruit growth stage. Although the productivity is not affected, those fruits cultivated with high N rates increase their size quickly, compared to other lemon plots with normal N levels. In each season, growers design a complex treatment schedule to manage their lemon fruit production, being those harvested at the beginning of the season fruits very sensitive, due to their peel characteristics. In this sense, our results showed that by maintaining the fertigation level during the lemon growth stage, without N incrementing, the fruit quality and shelf life were significantly improved.

Comment 2. In the introduction it is necessary to add how important good agricultural practices related to fertigation and nutrition are from the point of view of an agroecological approach (line 44-46).

Drip fertigation is commonly used for the application of fertilizers and water in all fruit and vegetable crops. An optimal fertigation management allows a consistent ap-plication of nutrients, improving its efficiency. This is an emergent property of agroecological systems, planning the strategies to create synergies between different system components.

Comment 3. In the materials and methods. I would add bibliography relating to citrus because so much has been done in Europe and in the Asian areas where citrus are cultivated.

Dear reviewer, we have improved the references about the effect of fertigation on citrus quality. We have used the last papers published in the field to introduce and discuss this document.

Comment 4. The use of best agricultural practices have demostrate to be the best methods to improve and sustain agricultural production, soil health, and the environment. Recent advances on effective need-based nutrient management, and the concept of precision agriculture, can also be explored to improve soil health and agricultural sustainability. For this reason and to accept the paper, in the part of the results must be emphasize how good agricultural practices, in addition to an advantage for the environment, lead to high quality fruit which is thus advantageous for human health.

Dear reviewer, in the paragraph below we are trying to answer this comment:

In the introduction and results section, we have shown the importance of antioxidant compounds of lemon fruits as follows (line 29-36 and line 145-148):

• External quality of lemon fruit is attributed to visual appearance, freshness and firm-ness, while internal quality properties are related to fruit flavour, taste and antioxidant capacity. Lemon fruit is well known as an important source of bioactive com-pounds, such as vitamin C, phenolic and flavonoids. Those compounds are involved in fruit senescence, decay resistance and they provide healthy properties to humans [2,3]. Thus, the development of strategies focused on increasing these bioactive compounds could be interesting for producers and consumers.
• Phenolic compounds, as well as ascorbic acid, are responsible for most of the antioxidant properties attributed to lemon fruits. These compounds play an important role in decreasing the effect of free radicals that are produced during the senescence process and promotes the human-healthy effects [17].

In the results section we have shown the importance of a proper management of the resources, adding new references and comments (line 159-175):

Those results showed that TPC in flavedo of lemons cultivated with IF at day 0 was 2.22 ± 0.04 g Kg -1, being significantly lower (p < 0.05) than those lemons raised in SF plot with a decrease of 18 % (Figure 1A). The effect of different fertigation strategies on phenolics during growth and ripening on the tree is still unknown. Previous results have shown the importance of the water volumes and the nutrient solutions applied through drip fertigation on the fruit quality [20]. In this sense, increasing the nutritive value (N, K, P and organic matter) in the soil substrate of peppers reduced TPC [21]. In mandarins, the application of K solutions increased TPC in juice [22]. Meanwhile, peaches fertigated with different doses of N showed that at high doses of N, lower concentrations of phenolics were observed [23]. These differences could be related to the different ripening stages of fruits at harvest, which is in accordance with the results shown in Figure 1A. Furthermore, a decrease in TPC and flavonoid content with an increase in N application has been previously reported in tomatoes and broccoli [24,25]. These studies showed the importance of an optimal N concentration in the solution used during the fertigation schedule to maintain a high TPC. Besides, previous results on nectarines showed the effect of a precise management to reduce the poly-phenol oxidase (PPO) activity and maintain a high TPC [26].

Finally, it is important to show the importance to apply that strategy in the environment, fruit quality and human-health, this information is in the conclusion of our experiment, we have rewritten this part, please find it below (line 307-314):

This work showed that the agronomical practices that growers apply to promote the optimal fruit size are drastically reducing its quality. Overall, the application of the standard fertigation strategy during the lemon fruit growth stage significantly improved the physicochemical quality of lemon fruits. Besides, that strategy maintained a high antioxidant capacity in the flavedo of lemons, delaying the senescence process and reducing their susceptibility to decay during postharvest cold storage. Therefore, growers must regulate the fertigation strategy to improve the sustainability of the crops and provide high-quality fruits to consumers.

Author Response File: Author Response.docx

Reviewer 2 Report

Dear authors,

Thank you for the opportunity to review this Manuscript (Effect of fertigation on the physicochemical quality and antioxidant system of 'Fino' lemon during postharvest storage). The objective of this paper was developed by comparing two plots; the first one with a standard fertigation (SF) and the second one with an intensive fertigation (IF). The yield per tree in the early harvest was higher in the IF plot than the SF plot, however total yield was similar in both fertigation strategies. The manuscript has important results but there is some aspect that should be reviewed by the authors.

 

PLEASE, THE EDITIONS SHOULD BE ADDED IN THE MANUSCRIPT AND ANSWERED IN THE LETTER

The title is good.

The abstract is clear and brings all information required. However, it is not clear the Material and Methods of the nutrient concentrations in nutritive solutions.

The introduction is good. No suggestions

The goals are clear.

In the “Materials and Methods” and “Results and Discussion” the topics are clear and help to understand and follow the study.

Explain how the irrigation was performed

Explain soil managements

There was the application of fertilizer in the soil

Explain the field condition in the study. How is soil used in this area

The results and discussion are clear.

Author Response

REVIEWER 2

 

Dear reviewer, we are very grateful for your useful comments which have helped to improve our original manuscript. Please find below you can find a detailed list of your comments and suggestions and the answer and modifications performed in the revised manuscript according to your suggestions. The new information added to the revised manuscript has been highlighted in blue ink and the English grammar has been revised according to your suggestion. Besides, English changes have been done using red ink.

Comment 1. Explain how the irrigation was performed (line 81)

Two plots of 8-year-old 'Fino' lemon trees grafted on Citrus macrophylla rootstock with an independent drip fertigation system were selected for this experiment. One plot was cultivated with an intensive fertigation (IF) strategy during flowering, fruit growth and fruit ripening stages, 721 trees were included in this plot.

Comment 2. Explain soil managements (line 79)

The soil management was the same in both plots. In this experiment, we used two plots of the same field and staff applied standard strategies for maintaining the health of the soil and plants. However, we have added the following phrase to emphasize this fact:

The soils were aridisol type composed of 45 % clay, 25 % loam and 33 % sand, the electric conductivity was 0.32 dS m-1 and a pH of 8.03. This field has been cultivated using standard agronomical practices. Two plots of 8-year-old 'Fino' lemon trees grafted on Citrus macrophylla rootstock with an independent drip fertigation system were selected for this experiment.

Comment 3. There was the application of fertilizer in the soil (line 85-86)

Dear reviewer, the fertilizer was applied in the soil using a drip fertigation system. Each plot had its own fertigation facilities. Therefore, we could apply an independent treatment. The fertilizers used for this experiment were organic liquid nitrogen and potassium oxide (K₂O).

Comment 4. Explain the field condition in the study. How is soil used in this area. (line 77-78)

The soil in this experiment has the following characteristics:

The soils were aridisol type composed of 45 % clay, 25 % loam and 33 % sand, the elec-tric conductivity was 0.32 dS m-1 and a pH of 8.03.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have included in the work what was requested. Thus the work is more fluent in explanation and can be accepted for publication