Effect of Regulated Deficit Irrigation (RDI) on the Growth and Development of Pear Fruit (Pyrus communis L.), var. Triunfo de Viena

Round 1

Reviewer 1 Report

The water scarce is most challange for the agriculture over the world, Herein lies the value of this study. But, there are some explainations have to be provided;

In introduction Lines 71 to 73, the author has to provide data about cultivated area and production ''In Colombia, 'Triunfo de Viena' is the most important pear variety in the Cundinamarca and  Boyacá regions, grown at altitudes between 2,400 and 3,000 m, where the plants manage  to accumulate 500-600 cold hours to break their rest,''

Author did not provide the LSD values for all Tables, Please put the LSD values under each Table or over each figure.

Line 217, Table 2, author classified the fruits in three categories 1, 2 and 3, Treatment 100% of ETc and 74% gave the highest No. of fruits for the bigger fruits diameter (class 1 and 2), but the average fruit weight was lower than Treatment ETc 60 , explain why? LSD value needed!

Line 266, author said ''This could be due to the fact that the water deficit was not severe,'' do the author think the deficit irrigation (60% ETc) not severe? what is  % for severe deficit irrigation?

author has to provide physiological mechanisms that help pear plants that received less water application how showed no significant reductions in terms of production, number of fruits per 422 tree and average weight of the fruit

The water scarce is most challange for the agriculture over the world, Herein lies the value of this study. But, there are some explainations have to be provided;

In introduction Lines 71 to 73, the author has to provide data about cultivated area and production ''In Colombia, 'Triunfo de Viena' is the most important pear variety in the Cundinamarca and  Boyacá regions, grown at altitudes between 2,400 and 3,000 m, where the plants manage  to accumulate 500-600 cold hours to break their rest,''

Author did not provide the LSD values for all Tables, Please put the LSD values under each Table or over each figure.

Line 217, Table 2, author classified the fruits in three categories 1, 2 and 3, Treatment 100% of ETc and 74% gave the highest No. of fruits for the bigger fruits diameter (class 1 and 2), but the average fruit weight was lower than Treatment ETc 60 , explain why? LSD value needed!

Line 266, author said ''This could be due to the fact that the water deficit was not severe,'' do the author think the deficit irrigation (60% ETc) not severe? what is  % for severe deficit irrigation?

author has to provide physiological mechanisms that help pear plants that received less water application how showed no significant reductions in terms of production, number of fruits per 422 tree and average weight of the fruit

regards,

Author Response

Dear Reviewer, below you can find the point-by-point responses.

Additionally, we attach the final text (Sustainability, 2539826, final revised text, 27-08-23, without authors), in which all changes are marked in red and where also the extensive English revision was made by a native English speaker reviser.

Thanks a lot for your recommendations.

Referee 1

In Introduction Lines 77-80, the author has to provide data about cultivated area and production in Colombia, Triunfo de Viena is the most important pear variety in Cundinamarca and Boyacá regions, grown at altitudes between 2,400 and 3,000 m, where the plants manage to accumulate 500-600 chilling hours to break their rest.

This information is now included in the Introduction text (lines 84-86 of final text).

Author did not provide the LSD values for all Tables. Please put the LSD values under each Table or over each figure.

LSD values were included in tables 1 and 2, but not in table 3 which corresponds to the coefficients of the regression equations and the means between the treatments are not presented and therefore, a comparison of means is not necessary.

Line 263-264, Table 2, author classified the fruits in three categories 1,2 and 3, Treatment 100% of ETc and 74% gave the highest No. of fruits for the bigger fruit’s diameter (class 1 and 2) but the average fruit weight was lower than Treatment ETc 60, explain why? LSD value is needed!.

The lower fruit weight obtained in 2015 (163.74 g) could have occurred because rainfall was 2.8 times lower in that year than in 2014, and even the treatment in which 60% ETC was applied in 2014 had a higher fresh weight (267.04 g) than that registered in plants irrigated with 100% ETc in 2015 (167.99 g), with a significant difference between the two years. The LSD values were included in the footnote of the Table.

Line 323-324, author said “This could be due to the fact that the water deficit was not severe”, do the author think the deficit irrigation (60% ETc) not severe? What is …% for severe deficit irrigation?

This could be due to the fact that the water deficit was not sufficiently severe, partly thanks to the rainfall and the fruits grew due to the reserve carbohydrates stored in the stems and roots and were able to accumulate dry matter during stress periods, without affecting the production, as reported in pear [36] and in Nules clementine [37]. The reduction of the volume of water applied to induce a severe stress is one that affects the production and quality of the fruit, but in our case, this was not what happened.

Author has to provide physiological mechanisms that help pear plants that received less water application how showed no significant reductions in terms of production, number of fruits per tree and average weight of the fruit.

As we answered in the previous point, the reserve carbohydrates stored in the stems and roots were able to accumulate dry matter in fruits during stress periods, without affecting the production, as observed in pear [33] and in Nules clementine [34].

According to Yang et al. (2022), when the environmental conditions were abundant and stable, the ratio of root to shoot was in a relatively stable interval, and this value was mainly determined by the genetic factors of the plants. However, when the external nutritional conditions change or under stress, the plant would automatically adjusted the distribution of nutrients to minimize the damage to the environment and was most conducive to the continuation of its species.

On the other hand, when the root was in a state of water deficit, under the regulation of some endogenous hormones (such as ABA), the aboveground part of the plant closed the stomata, decreased leaf area growth, reduced the shoot development to reduce water evaporation, which leaded to decrease of water demand. At the same time, more assimilation products were transferred to the underground part, and the roots grew thicker, which improved the soil WUE of plant.

In summary, the basic principle of water-saving during RDI was the treatment influenced the root-shoot ratio of plants through the management of soil moisture, controlled the root growth and aboveground parts of plants at the same time, increased the utilization of plants, reduced the vegetative growth and transpiration, so as to reduce the water demand of plants and irrigation water.

According to the above explanation of root-shoot balance theory, when plants were under stress, more nutrients would be transferred to reproductive growth, giving priority to ensuring the continuity of species. Because of this phenomenon, RDI won’t have too much negative affect on crop growth (especially fruit) with saving water. Some researchers believed that RDI would lead to a slight reduction in fruit yield, but others believed that early moderate water deficit would improve yields in some specific crops.

Yang, B.; Fu, P; Lu, J.; Ma, F.; Sun, X.; Fang, Y. Regulated deficit irrigation: an effective way to solve the shortage of agricultural water for horticulture. Stress Biol. 2022, 2, 28. https://doi.org/10.1007/s44154-022-00050-5

A summary of Yang et al., 2022 was included in the text (point 3.1, lines 335-340)

On the other hand, the authors suggest that ‘Triunfo de Viena’ pear not only possesses sufficient adaptive reserves but also a good ecological plasticity against hydric stress conditions in tropical highlands.  

Reviewer 2 Report

Expand the Abstract, considering the problem, objective, location, methodology, main results and conclusions

Line 25: replace water stress instead of sustainability.

Line 38: replace ETc instead of Etc.

Point 2.1: Include information on the geographic coordinates, height of the place, average maximum temperature, average minimum temperature and average annual precipitation.

Line 97: ETo was calculated using the FAO56 PM-ETo method? Explain.

Line 98: 2.09 and 2.03 are average values?

Line 105: How was ETc calculated? Explain the standard condition.

Lines 107 -109: Why were the treatments not the same in the years 2014 and 205? Explain.

Why were other variables such as plant height, leaf area index, effective root depth and percentage of soil cover per plant not considered?

Lines 117 -119: corresponds to Results.

Line 124: Why is no water potential at solar noon (Ψfn) data shown?

The water potential data was only measured in 2014 and not in 2015, which does not allow a year-on-year comparison. Explain.

Why weren't chemical quality data used on the fruits? For example soluble solids content. Explain

Line 169: What is the normal level of restoration?

Table 1: How was the dry weight obtained? Explain.

Table 1 an 2:  What is the difference in the weight of the fruits in the two tables (Fresh weight and Average fruit weight? Explain.

Line 204: is Table 2.

What is Figure 1A and 1B?

In Results it is not clear when irrigation resumption? What were the amounts of rainfall in the study periods (between irrigation and irrigation)? Was the amount of rain discounted for the application of the irrigation depth? Explain. Perhaps the rain masked the effects of the water deficit in the treatments with controlled deficit irrigation.

It would be interesting to generate data on water use efficiency.

Figure 2:  Does not show data on the depth of irrigation water.

Author Response

Dear Reviewer, below you can find the point-by-point responses.

 Additionally, we attach the final text (Sustainability, 2539826, final revised text, 27-08-23, without authors), in which all changes are marked in red and where also the extensive English revision was made by a native English speaker reviser.

Thanks a lot for your recommendations.

Referee 2

Expand the Abstract, considering the problem, objective, location, methodology, main results and conclusion.

The Abstract was expanded including these points.

Line 30: replace water stress instead sustainability.

This change was made.

Line 43: replace ETc instead of Etc

This change was made.

Point 2.1: Include information on the geographic coordinates, height of the place, average maximum temperature, average minimum temperature and average annual precipitation.

This change was made (lines 102-111).

Line 112: ETo was calculated? Explain the standard condition.

In the text we write: The mean potential evapotranspiration (ETo) values were calculated using the Penman-Monteith equation [23, 24] and showed values of 2.609 and 1.82.03 mm day^-1 in 2014 and 2015, respectively. The average percentage of the shaded area of the trees was 44.0% in the two years with an average area of 7.04 m2 with respect to the plantation framework (16 m2); crop coefficient (Kc) 0.8 and irrigation efficiency (ɳr) of 80%.To realize  the water balance, the following was determined: the effective precipitation by means of the S.C.S. (USDA Soil Conservation Service); which resulted in the restriction period a water depth of 67.6 and 48.3 mm (1.144 mm dia^-1 and 0.779 mm dia^-1) in the Control treatment, corresponding to 100% of TEc in 2014 and 2015, respectively. Determined as: ETc = (ETo *Kc*%A)/ɳr [25].

Explanation: ETo (Potential Evapotranspiration) is a measure of the amount of water that could be evaporated and transpired from a reference vegetated surface, under ideal climatic conditions. It is a useful value in water management and agriculture to estimate irrigation needs. One of the most common methods for calculating ETo is the Penman-Monteith method, which takes into account various climatic and physical factors.

The calculation of ETo using the Penman-Monteith method involves the following steps and components:

1. Solar Radiation: It is necessary to know the incident solar radiation at the specific location. This can be measured with weather stations or estimated from climate models.
2. Air Temperature: The maximum and minimum daily air temperature is required. These temperatures are used in degrees Celsius.
3. Relative Humidity: Relative humidity is necessary to determine the pressure of water vapor in the air.
4. Wind Speed: Wind speed is an important factor in the rate of evaporation and transpiration.
5. Atmospheric Pressure: Atmospheric pressure is used in calculations of the vapor pressure of water.
6. Constants: The Penman-Monteith method uses empirical constants to fit the calculations.

The calculation is done through the following formula:

ETo = (0.408 * Δ * (Rn - G) + γ * (900 / (T + 273)) * u2 * (es - ea)) / (Δ + γ * (1 + 0.34 * u2))

Where:

• ETo: Potential evapotranspiration in mm/day.
• Δ: Vapor pressure gradient (kPa/°C).
• Rn: Net radiation on the surface (MJ/m²/day).
• G: Heat flux in the ground (MJ/m²/day).
• γ: Psychrometric constant (kPa/°C).
• T: Average air temperature (°C).
• u2: Wind speed at 2 meters above the surface (m/s).
• es: Saturation vapor pressure (kPa).
• ea: Current vapor pressure (kPa).

Line 113: 2.09 and 2.03 are average values?

No, these are absolute values. The mean potential evapotranspiration (ETo), calculated with the Penman-Monteith equation [23, 24] were 2.6 and 1.8 mm day^-1 in 2014 and 2015, respectively.

Line 121: How was the ETc calculated? Explain the standard conditions.

ETc (Crop Evapotranspiration) is a measure of the amount of water that a specific crop evaporates and transpires from a vegetated surface under certain climatic conditions. To calculate the ETc, the previously calculated ETo (Potential Evapotranspiration) is used and adjusted according to the characteristics of the crop. The most common method for calculating ETc is the Kc (Crop Coefficient) method, which multiplies the ETo by a crop-specific coefficient.

The calculation of ETc using the Kc method involves the following steps:

1. Calculate ETo: First, calculate ETo using the Penman-Monteith method or another reliable method based on available weather data at the crop location.
2. Determine Crop Coefficient (Kc): Each crop type has a unique crop coefficient that reflects its characteristics and water needs in relation to ETo. The crop coefficient (Kc) varies throughout the crop life cycle, from planting to harvest, and is divided into different stages such as initial, development, and maturity. Kc values are found in agricultural tables and guides for different types of crops.
3. Calculate the ETc: Multiply the ETo by the crop coefficient (Kc) corresponding to the development stage of the crop:

ETc = ETo * Kc

The general formula to calculate the ETc at a specific stage of the crop would be:

ETc (in mm/day) = ETo (in mm/day) * Kc

Line 130-131: Why were the treatments not the same in the years 2014 and 2015? Explain.

The treatments were not the same in the two years, since there were no differences in 2014, the irrigation volume of the treatments was decreased in 2015, to evaluate what effect this decrease had. This explanation was included in the article’s text (lines 130-131).

Why were other variables such as plant height, leaf area index, effective root depth and percentage of soil cover per plant not considered?

The article concentrated in fruit growth variables. The plant height variable was not considered since the plants were adult (16-17 years old). Other suggested tests are destructive and could not be performed without affecting the development of the work.

Line 139-141 corresponds to Results.

This sentence was moved at the beginning of the Results and discussion chapter (lines 189-191).

Line 143-146: Why is no water potential at solar noon (Ψfn) data shown?

This potential is now shown in point 3.2.3, including table 4.

The water potential data was only measured in 2014 and not in 2015, which does not allow a year-on-year comparison. Explain.

The Ψfd and Ψfn presented values ​​that reflect the water levels in the soil, both at the beginning of the application of the treatments, and when the precipitation and irrigation events occurred, in the same way, it was possible to verify that the Ψfd and Ψfn reached lower values ​​than Ψa and Ψt, found by [46] because the fruits present at all times a higher proportion of water than the leaves and the stem. Table 4 shows the average values ​​within which the water potential of the fruit fluctuated for the year 2014.

We only wanted to verify that the water potential of the plant (Y) was more sensitive than that of the fruit (Yf), and indeed we verified it in 2014.

Why weren’t chemical quality date used on the fruits? For example, solids content. Explain.

The article concentrated in fruit growth variables; fruit quality variables are treated in other publications.

Line 169: What is the normal level of restoration?

Reduction of the volume of water until the production and quality of the fruit are not affected.

Table 1: How was the dry weight obtained? Explain.

The fruit dry weight was obtained by placing the tissues in a calibrated muffle at 70°C, until there was no further decrease in weight. This was included in Material and methods, point 2.2 (lines 170-171).

Table 1 and 2: What is the difference in the weight of the fruits in the two tables (fresh weight and average fruit weight) Explain.

Fresh weight: Was obtained with the scale, weighing individually 320 fruits in 2014 and of the 480 in 2015. This was included in Material and methods (lines 166-168).

Average fruit weight: Was obtained by dividing the total production per tree by the number of fruits per tree. This calculation was included as a foot note in Table 2.

Line 253: is Table 2

This change was made.

What is Figure 1A and 1B.

All figures were marked with A and B.

In Results it is not clear when irrigation resumption? What were the amounts of rainfall in the study periods (between irrigation and irrigation)? Was the amounts of rain discounted for the application of the irrigation depth? Explain. Perhaps the rain masked the effects of the water deficit in the treatments with controlled deficit irrigation.

It was explained that, with the calculation of the ETc, an irrigation depth of 67.6 and 48.3 mm was determined in the restriction period in the Control treatment, corresponding to 100% of the ETc in 2014 and 2015, respectively. The irrigation frequency was 2 days. In figures 1 and 3, the restriction period is indicated, clearly defined in the text from which day to which day, each year. Figure 2 shows the rainfall, and the text indicates the rainfall in the restriction period and the volume of water supplied in the same period. And indeed, as explained in the text, there was an influence of precipitation, because in 2015, it was 2.8 less than in 2014, and this is reflected in the results. And it is obvious that when it rained the irrigation was not applied.

Mean effective precipitation, 66.41 29.18 mm/month, in 2014 and 2015 respectively. The total precipitation (Pt) in the period from November 2013 to April 2014 was 465.4 mm. The (Pt) from September 2014 to March 2015 was 233.4 mm.

It would be interesting to generate data on water use efficiency.

This parameter cannot be taken into consideration in this manuscript since the work is finished and for the calculation of this parameter a different arrangement is required than the one made for the present work.

Figure 2: Does not show data on the depth of irrigation water.

This point is explained with reference to volumetric humidity (qv), now included in the document (lines 192-203).

Reviewer 3 Report

The article examines a current issue related to water scarcity and how it affects productivity and quality.

Fruit crops (including pear) are sensitive to irrigation. I was impressed by how detailed the impact of regulated deficit irrigation was considered.

In irrigation, the depth of the active soil layer, which participates in evapotranspiration, is important. Here I did not understand how this depth was determined - apparently it is not fixed. I looked at the cited articles, but I didn't find an explanation in them either.

Attached is an article about the developed model - scheduling and water balance model ISAREG (Teixeira and Pereira, 1992, Liu et al., 1998, Pereira et al., 2003c); the results of those analyzes were used to classify the soil in three TAW categories paragraph 100-104- All this doesn't sound convincing to me!

Leaving that aside, the methods for extracting the experience are very well described. In the results section, it is noted that there are no statistically significant differences between treatments. In such studies, it is good to make observations for a minimum three-year period. Then it is expected that the results will be more representative.

Production depends on the season, climatic conditions, intensity and duration of applied water stress. I suggest that the authors do a statistical analysis for the influence of the individual factors.

In my opinion, a detailed analysis of the obtained results has been made - yield parameters, number of fruits, fruit weight, fruit growth rates, etc. The influence of regulated water deficit is very well interpreted.

Regarding the conclusions, I would suggest that they be specified for the future. Here, benefits should be specifically highlighted and figures quoted. The authors lose from detailed explanations.

Author Response

Dear Reviewer, below you can find the point-by-point responses.

 Additionally, we attach the final text (Sustainability, 2539826, final revised text, 27-08-23, without authors), in which all changes are marked in red and where also the extensive English revision was made by a native English speaker reviser.

Thanks a lot for your recommendations.

Referee 3

In irrigation, the depth of the active soil layer which participates in evaporation is important. Here I did not understand how this depth was determined – apparently it is not fixed. I looked at the cited articles, but I didn´t find an explanation in the either.

This point is explained with reference to volumetric humidity (qv), now included in the document (lines 192-203).

Attached is an article about the developed model – scheduling and water balance model ISAREG (Teixeira and Pereira, 1992, Liu et al., 1998. Pereira et al., 2003c), the results of those analyses were used to classify the soil in three TAW categories, paragraph 100-104 – All doesn´t sound convincing to me!

The inclusion of volumetric humidity (qv) explains much related to this topic (lines 192-203).

Leaving that aside, the methods for extracting are very well described. In the results section, it is noted that there are no statistically significant differences between treatments. In such studies, it is good to make observations for a minimum of three-year period. Then it is expected that the results will be more representative.

In fact, for reliable data, the longest periods of time possible should be taken into consideration, however our work is finished, and we consider that two years of evaluation offer sufficiently contrasting information to have conclusive results in the study area. And the very few differences between years mean that there were no reductions in growth and fruit yield which is very positive.

Production depends on the season, climatic conditions, intensity, and duration of applied water stress. I suggest that the authors do a statistical analysis for the influence of the individual factors.

The conditions of the environmental supply have a great influence on the yield of the plants, however, since in the present work the objective was to evaluate the deficit irrigation on the production, the climatic conditions were equivalent for all the treatments during each year. therefore, the variable that influenced performance was each of the treatments implemented.

Regarded the conclusions, I would suggest that they be specified for the future. Here, benefits should be specially highlighted, and figures quoted. The authors lose from detailed explanations.

Because of your recommendation we changed the Conclusion text (lines 511-550).

Round 2

Reviewer 1 Report

LSD values has to be inserted in the Tables not in the text under Tables

MS English need to be improved

Author Response

Dear reviewer,

We inserted the LSD values in the two tables. Also the text of the article was revised by the English-Service ot MDPI, improving this last version.