Evapotranspiration Partition and Dual Crop Coefficients in Apple Orchard with Dwarf Stocks and Dense Planting in Arid Region, Aksu Oasis, Southern Xinjiang

Round 1

Reviewer 1 Report

Indicate the characteristics of the sensors, datalogger and location of the agroclimatic station used. Only a commercial reference is indicated.
For the use of equation 1, indicate how the surface runoff, the upward capillary flow into the root zone and the drainage have been measured. Explain the methodology followed and the equipment used.

Describe the lysimeters used and include photographs with their installation and location.
Indicate the characteristics of the soil moisture sensors used, the installation method, the separation from the tree trunk and the drippers, and the characteristics of the data collection equipment used.
Explain the methodology followed to determine bulk density, field capacity and wilting point, shown in table 1.
Why did you select W1 of 13.5mm, W2 of 18mm, W3 of 22.5mm, W4 of 27mm, and W5 of 31.5mm?
Expand and improve the conclusions according to the results obtained.

Author Response

Response to Reviewer Comments

(Manuscript Number: Agriculture-1443643)

Note: The line numbers mentioned by reviewers in the comments are kept same as those in early submission, whereas the line numbers mentioned in the responses for the corresponding comments line are the new line numbers in modified version of manuscript.

Reviewer #1

Comment 1: Indicate the characteristics of the sensors, datalogger and location of the agroclimatic station used. Only a commercial reference is indicated.

Response: Thanks for your suggestion. The HOBO weather station (U30-NRC) used in this experiment has a HOBO U30 USB data collector, an air pressure sensor of S-BPB-CM50, a rain sensor of S-RGB-M002, an air temperature and humidity sensor of S-THB-M002, a wind speed sensor of S-WSB-M003, and a pyranometer of S-LIB-M003. The automatic weather station was installed an open filed inside the orchard, about 100 m to the experimental plots. (Lines 167-173)

Comment 2: For the use of equation 1, indicate how the surface runoff, the upward capillary flow into the root zone and the drainage have been measured. Explain the methodology followed and the equipment used.

Response: Thanks. The Darcy’s law was used to estimated R and Dw, indicating that both R and Dw were negligible as low irrigation rate, the hydraulic properties of sandy loam soil, and groundwater table. Under the condition of low amount of irrigation and rainfall as well as flat topography, R was negligible. (Lines 141-144)

Comment 3: Describe the lysimeters used and include photographs with their installation and location.

Response: Thank you. Soil evaporation was measured with microlysimeters, which were installed between apple trees (Figure 3a). The microlysimeter was made of stainless steel, and consisted of an inner and outer tank. The diameter of the inner and outer tank was 10.0 cm and 12.0 cm, respectively (Figure 3b). The outer tank was fixed in the soil with its top edge leveling with the soil surface. To fill soil into each inner tank with an intact soil core, the inner tank was forced into the soil under drip line with the top leveling with the soil surface, then pull out and sealed the base with a plastic film. The microlysimeters were weighted at 10:00 a.m. The procedure of soil evaporation measurement by using microlysimeters was similar to the experiment of Gao et al. [36]. (Lines 184-192)

[34] Gao, Y.; Duan, A.; Qiu, X.; Li, X.; Pauline, U.; Sun, J.; Wang, H. Modeling evapotranspiration in maize/soybean strip intercropping system with the evaporation and radiation interception by neighboring species model. Agr. Water. Manage. 2013, 128, 110-119.

Comment 4: Indicate the characteristics of the soil moisture sensors used, the installation method, the separation from the tree trunk and the drippers, and the characteristics of the data collection equipment used.

Response: Thanks for your suggestion. Soil water content was measured by the S-SMC-005 soil moisture sensors, which were buried at the depth of 20 cm, 40 cm, 60 cm, 80 cm, 100 cm and 120 cm, with measurement range of 0-0.55 m3 /m3 and measurement accuracy of ± 0.031 m3/m3 (HOBO, Onset, MA, USA). Under the drip lines, auger a 7-cm hole to the depth at which the sensor was to be installed, insert the sensor into the undisturbed soil by a PCV pipe with a notch cut in the end, then remove the PVC pipe and backfill the hole. The soil moisture data were recorded with the HOBO-U30 data logger every 1 h. (Lines 144-151)

Comment 5: Explain the methodology followed to determine bulk density, field capacity and wilting point, shown in table 1.

Response: Thanks. The bulk density was measured by the core method with a solid ring, the field capacity was obtained by the plot irrigation method, and the wilting point was obtained by measuring the soil moisture content under 15 bar by using the pressure membrane meter method. (Lines 101-104)

Comment 6: Why did you select W1 of 13.5mm, W2 of 18mm, W3 of 22.5mm, W4 of 27mm, and W5 of 31.5mm?

Response: Thank you. In the arid oasis of Aksu, southern Xinjiang, the irrigation rate of 31.5 mm was primarily scheduled for apple trees. In order to optimize irrigation scheduling of apple orchard, the ±20% and ±40% changes in irrigation rate of 22.5 were designed in this study. (Lines 119-121)

Comment 7: Expand and improve the conclusions according to the results obtained.

Response: In this study, irrigation was controlled with the difference between ET0 and P, which could be used as a threshold for automatic irrigation system. The results could provide irrigation guidance for large-scale orchards with DCHD in arid regions in southern Xinjiang. Moreover, the method for determining crop coefficients and optimizing irrigation scheduling could be adopted to develop irrigation management for orchards in arid and semi-arid regions. To improve fruit yields and WP of orchards, knowledges of plant healthy-growing water demand need to be revealed to improve irrigation management in future. (Lines 364-371)

Author Response File: Author Response.docx

Reviewer 2 Report

I have minor comments that I would recommend addressing before final decision:

- Title

-- I would like to see “arid climate” or “arid region” in the title.

- Introduction:

--- Its better to talk shortly about rainfall interception in arid and semiarid orchard of world, as rainfall interception is important in evapotranspiration.

- Materials and methods:

--- Add information about studied trees (age, distance between trees, DBH, height, LAI, PAI, canopy closure, crown width, etc.).

--- Figure 1: In section (a) of this figure, determine that what is your mean by “High” and “Low” (I supposed its elevation above sea level).

--- Figure 2: replace “year” instead of “season”

--- Line 172: Its better to use Nash-Sutcliffe index instead of index of agreement as an evaluation metric.

--- Line 187: Add a software for statistical analysis.

- Conclusion:

 --- According to your conclusion, it would be nice to add some implications and also future direction for other researchers.

Author Response

Response to Reviewer Comments

(Manuscript Number: Agriculture-1443643)

Note: The line numbers mentioned by reviewers in the comments are kept same as those in early submission, whereas the line numbers mentioned in the responses for the corresponding comments line are the new line numbers in modified version of manuscript.

Reviewer #2

I have minor comments that I would recommend addressing before final decision:

Title

Comment 1: I would like to see “arid climate” or “arid region” in the title.

Response: Thanks for your suggestion. The title was revised as ‘Evapotranspiration partition and dual crop coefficients in apple orchard with dwarf stocks and dense planting in arid region, Aksu oasis, southern Xinjiang’. (Lines 2-4)

- Introduction:

Comment 2: It’s better to talk shortly about rainfall interception in arid and semiarid orchard of world, as rainfall interception is important in evapotranspiration.

Response: Thank you. Rainfall interception plays an important role in plant evapotranspiration, especially in arid region. It refers to the process that the total rainfall falling on the plant surface is captured, retained and finally evaporated from the leaves, stems and branches of the plant. Studies have shown that the canopy interception of fruit trees was about 26 mm [24]. Meanwhile, the rainfall intercepted by plant canopy accounts for 20 ± 8% of the total glob-al rainfall [25]. (Lines 69-74)

[24] Li, X.; Shi, P.; Yang, X.; He, L.; Kang, S. Water consumption variation and growth of apple trees under drip irrigation in Shiyanghe river basin of Gansu Province. J. Water Resour & Water Eng. 2005, 16 (1), 19-23.

[25] Good, S. P.; Noone, D.; Bowen, G. Hydrologic connectivity constrains partitioning of global terrestrial water fluxes. Sci. 2015, 349, 175-177.

- Materials and methods:

Comment 3: Add information about studied trees (age, distance between trees, DBH, height, LAI, PAI, canopy closure, crown width, etc.).

Response: The average height, diameter at breast height, and crown diameter of apple trees were 3.3 m, 39.6 mm, and 1.75 m, respectively. During the apple growing season, the ground coverage and leaf area index ranged from 0.39 to 0.52, and from 1.17 to 2.93, respectively. (Lines 112-117)

Comment 4: Figure 1: In section (a) of this figure, determine that what is your mean by “High” and “Low” (I supposed its elevation above sea level).

Response: Yes, it means elevation above sea level.

Comment 5: Figure 2: replace “year” instead of “season”

Response: Done. (Line 134)

Comment 6: Line 172: It’s better to use Nash-Sutcliffe index instead of index of agreement as an evaluation metric.

Response: Thanks for your suggestion. We changed the index of agreement to Nash-Sutcliffe index, as shown in Eq. (7) (Line 204). The results of Nash-Sutcliffe index were shown in Table 4 and Figure 4.

Comment 7: Line 187: Add a software for statistical analysis.

Response: The software package of DPS16.05 (Tang and Zhang et al., 2012) was used for statistical analysis. (Line 217)

Tang, Q.; Zhang, C. Data processing system (DPS) software with experimental design, statistical analysis and data mining developed for use in entomological research. Insect. Science. 2013, 20 (2), 254-260.

Comment 8: Conclusion: According to your conclusion, it would be nice to add some implications and also future direction for other researchers.

Response: In this study, irrigation was controlled with the difference between ET0 and P, which could be used as a threshold for automatic irrigation system. The results could provide irrigation guidance for large-scale orchards with DCHD in arid regions in southern Xinjiang. Moreover, the method for determining crop coefficients and optimizing irrigation scheduling could be adopted to develop irrigation management for orchards in arid and semi-arid regions. To improve fruit yields and WP of orchards, knowledges of plant healthy-growing water demand need to be revealed to improve irrigation management in future. (Lines 364-371)

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Accept in present form