Solar Fertigation: A Sustainable and Smart IoT-Based Irrigation and Fertilization System for Efficient Water and Nutrient Management

Round 1

Reviewer 1 Report

This work proposes a solar fertigation system that monitors multidimensional parameters of the agricultural environment for precise irrigation and fertilization. The topic of this work fits the scope of the journal and is of scientific significance. Nonetheless, there are some important concerns that the author needs to address before considering publication. These concerns are detailed below:

 

1) This reviewer thinks that the sentence along lines 13-17 is a bit confusing. It says that: “…the agronomic model of an innovative solar power – IoT smart automated irrigation system…”. Agronomic models should be integrated with the intelligent system. Not “…model of …system”. And, not “…fertigation is…system”.

2) In line 76, is the sentence “…, but more studies using medium or long-term…” correct?

3) In lines 89-90, check if this is " Solar fertigation…" and "…with IoT…". If they are without "the", they sounded better to me.

4) In lines 91-93, please, rephrase. Make it simpler and clearer.

5) In line 94, “the experimental setup…”, not “the experimental set up…”.

6) This reviewer thinks that the sentence along lines 101-102 is a bit misleading. It says “Solar fertigation is a low-cost WSN…”. I guess it means " Solar fertigation depends on low-cost WSN...".

7) lines 106-108, please, rephrase. The functions and application scenarios of the system should be expressed more clearly.

8) Is the system studied in this manuscript based on references [24-25]? Compared with the references [24-25], what is the uniqueness of the system?

9) Lines 139-141, explain better. This sentence meaning is difficult to get.

10) In line 182, “…database…” not “…data-base…” and “…environment,…” not “…environmental,…”.

11) In line 204, there should be no spaces before "where...".

12) In lines 223-233, the application and disadvantage of P-M model was described many times. Please, rephrase.

13) In line 235, “The use of…” not “Moreover, the use of…”.

14) In line 272, there should be no spaces before "where...".

15) In lines 306 and 312, “zr” represents “root zone”. In line 316, “zr” represents rooting depth. The abbreviations are inconsistent in meaning. Then, does “rooting depth” have the same meaning as “root depth”? It is not recommended to define the same abbreviation more than once. Abbreviations should remain unchanged after definition.

16) In lines 316 and 341, there should be no spaces before "where...".

17) In lines 341 and 342, “θFC” and “θWP” should be “θ_FC” and “θ_WC”.

18) In line 354, there should be no spaces before "where...".

19) In the “crop database ” Section, it is suggested to utilize Tables to show parameters such as kc to make the paper clearer.

20) In Section 2.1.5, what types of sensors are used in the smart irrigation system? Are these sensors all isomorphic? What protocols does the system use to access these sensor data?

21) The details of the platform in Figure 3 are not clear.

22) In line 557, there should be no spaces before "where...". The same problem appears in many parts of the manuscript. The grammar should also be paid more attention. Please check them.

23) In Section 3.3, three models are introduced. The manuscript mentions " At the present time, the irrigation strategy of the system is based on Hargreaves–Samani (H–S)" in Section 2.1.1. What kind of model does the system adopt? If multiple models are applied, what rules does the system rely on to schedule different models? The same problem should be explained in Section 3.4.

24) The format of Equation (13)-(16) is wrong.

25) The manuscript describes a variety of agronomic models, so how do determine the amount of irrigation, fertilization, and fertilizer type?

26) Section "Results" and "Discussion" mainly describe the effect of ETo estimation. Does the system improve crop yield or quality? Or how much fertilizer or water is saved?

Author Response

Reviewer 1

1. This work proposes a solar fertigation system that monitors multidimensional parameters of the agricultural environment for precise irrigation and fertilization. The topic of this work fits the scope of the journal and is of scientific significance. Nonetheless, there are some important concerns that the author needs to address before considering publication. These concerns are detailed below:

Thank you for the positive assessment of the manuscript. All the suggestions are successfully implemented.

 

2. This reviewer thinks that the sentence along lines 13-17 is a bit confusing. It says that: “…the agronomic model of an innovative solar power – IoT smart automated irrigation system…”. Agronomic models should be integrated with the intelligent system. Not “…model of …system”. And, not “…fertigation is…system”.

Thank you for an important comment. The sentence is now updated as This study describes the agronomic models should be integrated with the intelligent system which schedules the irrigation and fertilization according to the plant needs, and monitors and maintains the desired soil moisture content via automatic watering.

 

3. In line 76, is the sentence “…, but more studies using medium or long-term…” correct?

We have double checked and found that Ferrise et al. (2015) has performed crop modelling and analysis on different environmental conditions. The study collected several months and years of data and performed their analysis to forecast crop yield and harvest. Due to these factors, the medium- or long-term meteorological forecasts are being mentioned in our study.

 

4. In lines 89-90, check if this is " Solar fertigation…" and "…with IoT…". If they are without "the", they sounded better to me.

The sentence is now updated accordingly.

 

5. In lines 91-93, please, rephrase. Make it simpler and clearer.

Thank you. The sentence is now updated as recommended: A novel irrigation control strategy using a hybrid predictive model based on weather and crop data, and real-time sensors were described.

 

6. In line 94, “the experimental setup…”, not “the experimental set up…”.

Thank you, the sentence is now updated.

 

7. This reviewer thinks that the sentence along lines 101-102 is a bit misleading. It says “Solar fertigation is a low-cost WSN…”. I guess it means " Solar fertigation depends on low-cost WSN...".

Thank you, the comment is implemented accordingly: Solar fertigation depends on low-cost WSN.

 

8. lines 106-108, please, rephrase. The functions and application scenarios of the system should be expressed more clearly.

The suggestion is now updated as recommended by the reviewer: The studied system is an automatic fertigation system that elaborates crop water needs and collects historic and real-time data. It achieves effective utilization of water and fertilizers with the help of an automatic fert-irrigation system for crops by taking into consideration the plant and soil needs.

 

9. Is the system studied in this manuscript based on references [24-25]? Compared with the references [24-25], what is the uniqueness of the system?

The project consists of different consortiums and experts. The manuscript of reference [24, 25] analysed the engineering aspects of the solar fertigation and IoT of the same system. This manuscript presents the agronomic perspectives (DSS and agronomic parameters) of solar fertigation and its potential for irrigation scheduling in crop fields.

Visconti et al. [24] analysed the low-cost wireless sensor network of the solar-powered fertigation system based on remotely controlled by the farmer; however, Valecce et al. [25] developed the IoT architecture of the solar fertigation system.

Our studies extended the work efficiency of the solar fertigation system by deep analysis of the crop and soil factors.

 

10. Lines 139-141, explain better. This sentence meaning is difficult to get.

Thank you. The sentences mentioned, are now updated presenting a clear idea. Such as The DSS is integrated with the desktop platform used on several devices, such as personal computers, laptops, mobile phones or tablets and users can monitor and manage the fertigation activities.

 

11. In line 182, “…database…” not “…data-base…” and “…environment,…” not “…environmental,…”.

Thank you, the suggestion is updated accordingly.

 

12. In line 204, there should be no spaces before "where...".

Thank you, the suggestion is updated accordingly.

 

13. In lines 223-233, the application and disadvantage of P-M model was described many times. Please, rephrase.

Thank you very much, we agree with an important suggestion and the sentences are updated as recommended: P–M model is recognized as the standard method for ETo assessment which provides the best performance in Mediterranean environments [26-28] (Berengena and Gavilán 2005; Allen et al. 1998; Paredes et al. 2020). However, the need for collecting a relatively large number of parameters (e.g., relative humidity of the air, solar radiation or wind speed) in different climates, which are generally difficult to estimate with good accuracy, restricts the extensive utilization of this model [28] (Paredes et al. 2020). Therefore, alternative methodologies requiring lower cost observations have been developed.

 

14. In line 235, “The use of…” not “Moreover, the use of…”.

Thank you, the suggestion is updated accordingly.

 

15. In line 272, there should be no spaces before "where...".

Thank you, the suggestion is updated accordingly.

 

16. In lines 306 and 312, “zr” represents “root zone”. In line 316, “zr” represents rooting depth. The abbreviations are inconsistent in meaning. Then, does “rooting depth” have the same meaning as “root depth”? It is not recommended to define the same abbreviation more than once. Abbreviations should remain unchanged after definition.

Thank you, the suggestion is updated accordingly.

 

17. In lines 316 and 341, there should be no spaces before "where...".

Thank you, the suggestion is updated accordingly.

 

18. In lines 341 and 342, “θFC” and “θWP” should be “θ_FC” and “θ_WC”.

Thank you for the suggestion. That is updated now accordingly.

 

19. In line 354, there should be no spaces before "where...".

Thank you for the suggestion. That is updated now accordingly.

 

20. In the “crop database ” Section, it is suggested to utilize Tables to show parameters such as kc to make the paper clearer.

We appreciate the comment. The table is developed as suggested: A database for nutrients and irrigation management of nine crops was developed, furthermore, a study for other crops is in progress.

Table 1. Crop database of different crops and their important parameters.

Crops/Parameters	p-factor	Temperature requirement (°C)	Root depth (zr) (m)	Crop coefficient (kc)	Yield factor (ky)	Fertilizers (N-P-K) (kg ha-1)	Crop water requirement (mm growing season-1)	References
Citrus (Citrus sinensis and Citrus limon	0.5	23-30	1.2	0.70	0.8-1.1	100-35-50	900-1200	[38] (Bhite et al. 2017)
Olive (Olea europaea)	0.65	15–25	6.0	0.70	0.2	200-55-160	600-800	[39] (Ben-Gal et al. 2017)
Soybean (Glycine max)	0.5-0.9	18-35	1.0	1.15	0.2-1.0	20:40:20	450-700	[40] (Shen et al. 2018)
Potato (Solanum tuberosum)	0.9	18-20	1.0	0.5	0.85	34-0-0	500-700	[41] (Jahanzad et al. 2017)
Cabbage (Brassica oleracea var. capitata)	0.4	20-25	0.5	0.95	0.60	45:45:45	380-500	[40] (Shen et al. 2018)
Onion (Allium cepa)	0.3	20-30	0.6	0.75	0.3	60–25–45	350-550	[39] (Ben-Gal et al. 2017)
Pepper (Capsicum annuum)	0.3	18-27	0.8	0.9	1.1	5-10-10	600-1250	[42] (Geisseler et al. 2020)
Tomato (Lycopersicon esculentum)	0.3	18-25	1.0	0.9	0.4	200:250:250	400-600	[42] (Geisseler et al. 2020)
Watermelon (Citrullus lanatus)	0.4	21–29	0.8	0.75	0.3	80–25–35	600-800	[1, 43] (FAO Land and Water; FAOSTAT 2001)

 

21. In Section 2.1.5, what types of sensors are used in the smart irrigation system? Are these sensors all isomorphic? What protocols does the system use to access these sensor data?

Thank you, the sensors and protocol detail are updated accordingly:

The types of sensors used in the smart irrigation system are real-time fertigation monitoring sensors, such as DHT22, SHT11 and SEN0193 for environmental and soil parameters. The sensor nodes are isomorphic and non-rechargeable with the initial energy being the same as E₀.

MQTT is an extremely simple and lightweight messaging protocol, designed for constrained devices and low-bandwidth, high-latency or unreliable networks. All content is delivered to the user interface using MQTT protocol and ActiveMQ message broker deployed on AWS as software as a service [25] (Valecce et al. 2019).

 

22. The details of the platform in Figure 3 are not clear.

Thank you for the comment. The details of the platform are now updated, as a) describes different fields and the particular crop and weather information. It also shows the power voltage and active power of the system; b) shows different crops and their particular parameters during their different growth stages and stage lengths; c) presents different zones of fertigation of crops, seedling and harvest data, types, and row spacings. It also shows the activation and deactivation of the fertigation in that particular zone of the field; d) shows the level and quantity of fertilizers in a container; e) irrigation and fertilization schedules; f) solar fertigation remote application through which farmers could monitor and control the fertigation in different fields.

 

23. In line 557, there should be no spaces before "where...". The same problem appears in many parts of the manuscript. The grammar should also be paid more attention. Please check them.

Thank you, the suggestion is updated accordingly.

 

24. In Section 3.3, three models are introduced. The manuscript mentions " At the present time, the irrigation strategy of the system is based on Hargreaves–Samani (H–S)" in Section 2.1.1. What kind of model does the system adopt? If multiple models are applied, what rules does the system rely on to schedule different models? The same problem should be explained in Section 3.4.

Thank you, the concept is now updated as requested: At the present time, the choice of multiple model utilization is not performed but the model is based on H-S formula. In the future, it would be possible to add multiple empirical methods according to the available data and environmental conditions. At the present time, the irrigation strategy of the system is based on H–S, however, the P–M formula could also be uploaded. Furthermore, an experimental setup of seven ET crop models is reported in section 3 and was used for the implementation of the ET equation in the DSS.

 

25. The format of Equation (13)-(16) is wrong.

Thank you, we appreciate this important aspect. We just double-checked and validated the equations (13-16). The spacing issue has now been corrected accordingly.

 

26. The manuscript describes a variety of agronomic models, so how do determine the amount of irrigation, fertilization, and fertilizer type?

For the amount of irrigation, the H-S formula was used by the system (as described previously). While, for the fertilization, the crop database and parameters were taken into consideration by the solar fertigation system.

 

27. Section "Results" and "Discussion" mainly describe the effect of ETo estimation. Does the system improve crop yield or quality? Or how much fertilizer or water is saved?

The setup of the system is ready and further development and experimental activities are planned to quantity the amount of irrigation water, fertigation, and crop yield and quality; however, the study would improve the crop yield and quality by 20-30%.

Reviewer 2 Report

* Paragraph about the crop database (l. 394 to 426): display this as a table instead of continuous text, which gives better overview.
Furthermore, you introduce these values, but where are they used in the paper? If they are used in the web platform: where do they contribute to the computation?

* Fertigation system: You describe the system only very briefly in the introduction paragraph of section 3 (l. 491 to 504). Give more details about the system -- according to the abstract and summary of the paper, the goal is to validate the ETo prediction of the system, so this should be the focus of the paper. (Some of the marks given above are reduced because of these reasons) You should at least answer the following questions:
* How big are the fields? How many sensors of which type are placed at which position?
* Which wireless communication technology is used to collect the data from the sensors? How is the sensing equipment powered?
* How often is the data collected?
* Where is the data processed?
* How does the fertigation system compute the ETo values from the sensor data? The models which you list only specify how to compute ETo from the weather station data.

* There are typesetting mistakes below l. 664 (orphaned starting and
  ending indices)

* Fig. 4: labels on x axis: typesetting mistake: remove non-English characters

Author Response

Reviewer 2

1. Paragraph about the crop database (l. 394 to 426): display this as a table instead of continuous text, which gives better overview.

We appreciate the comment. The table is developed as suggested:

A database for nutrients and irrigation management of nine crops was developed, furthermore, a study for other crops is in progress.

Table 1. Crop database of different crops and their important parameters.

Crops/Parameters	p-factor	Temperature requirement (°C)	Root depth (zr) (m)	Crop coefficient (kc)	Yield factor (ky)	Fertilizers (N-P-K) (kg ha-1)	Crop water requirement (mm growing season-1)	References
Citrus (Citrus sinensis and Citrus limon	0.5	23-30	1.2	0.70	0.8-1.1	100-35-50	900-1200	[38] (Bhite et al. 2017)
Olive (Olea europaea)	0.65	15–25	6.0	0.70	0.2	200-55-160	600-800	[39] (Ben-Gal et al. 2017)
Soybean (Glycine max)	0.5-0.9	18-35	1.0	1.15	0.2-1.0	20:40:20	450-700	[40] (Shen et al. 2018)
Potato (Solanum tuberosum)	0.9	18-20	1.0	0.5	0.85	34-0-0	500-700	[41] (Jahanzad et al. 2017)
Cabbage (Brassica oleracea var. capitata)	0.4	20-25	0.5	0.95	0.60	45:45:45	380-500	[40] (Shen et al. 2018)
Onion (Allium cepa)	0.3	20-30	0.6	0.75	0.3	60–25–45	350-550	[39] (Ben-Gal et al. 2017)
Pepper (Capsicum annuum)	0.3	18-27	0.8	0.9	1.1	5-10-10	600-1250	[42] (Geisseler et al. 2020)
Tomato (Lycopersicon esculentum)	0.3	18-25	1.0	0.9	0.4	200:250:250	400-600	[42] (Geisseler et al. 2020)
Watermelon (Citrullus lanatus)	0.4	21–29	0.8	0.75	0.3	80–25–35	600-800	[1, 43] (FAO Land and Water; FAOSTAT 2001)

 

2. Furthermore, you introduce these values, but where are they used in the paper? If they are used in the web platform: where do they contribute to the computation?

These values and data are of particular importance. The data supported the system is running the fertilization quantity at different periods of the day. This database is based on crop database and parameters which provides the exact requirement and needs of the crops and soil at the particular environmental condition and temperature.

 

3. Fertigation system: You describe the system only very briefly in the introduction paragraph of section 3 (l. 491 to 504). Give more details about the system -- according to the abstract and summary of the paper, the goal is to validate the ETo prediction of the system, so this should be the focus of the paper. (Some of the marks given above are reduced because of these reasons) You should at least answer the following questions:

We appreciate the comment. The system is now more clearly described and updated in the details as:

Solar fertigation depends on a low-cost WSN, almost autonomous from the energy point of view, monitors and transmits locally or towards the on-cloud software platform. The prototype detected soil and environmental parameters for checking crops growth directly on the field and for sustaining farmers in the decision-making phases connected to the growth processes of the cultivated crops [24] (Visconti et al. 2020).

The studied system is an automatic fertigation system that elaborates crop water needs and collects historic and real-time data. It achieves effective utilization of water and fertilizers with the help of an automatic fert-irrigation system for crops by taking into consideration the plant and soil needs.

It is designed and developed with the ability of intelligent decision making in terms of crop watering on the basis of ETc considering features like crop type, growth stage, weather data and conditions, humidity, temperature, and soil and plant sensors.

The proposed fertigation system consists of physical modules electrically powered by a photovoltaic power supply and a cloud computing infrastructure for managing the physical modules in an automated way. In fact, by means of the informatics infrastructure, it is possible to control and activate the fertigation phases according to the crop type and their growth phase, create a history of operations and share data by using a tracking system in reference to environmental conditions.

A detailed architecture of the proposed system, sensor node installation, design and management, WSN connection, IoT, data acquisition from sensor nodes, connections and networks, fertigation system, hardware, and software of the fertigation system is described in Visconti et al. (2020) [24] and Valecce et al. (2019) [25].

DSS is a major component in charge of taking the final decision on the quantity of water to be irrigated, or equivalently, the time to irrigate considering continuous water flow. This decision is considered intelligently on the basis of the information delivered by soil sensors, weather conditions, crop type and IoT analysis. The aim of this component, therefore, is to operate as a human expert in decision-making processes for the optimization of irrigation and assisting the farmer. The DSS further aims to assure a rational use of fertilizers, water resources and ultimately a reduced environmental impact. The method allows for integration and optimizes the management of the traditional cropping systems with the current technologies.

 

4. How big are the fields? How many sensors of which type are placed at which position?

The study consists of different regions in which the range of fields was estimated from 10 to 12 hectares.

One weather sensor (Temperature, humidity, wind speed and direction) was deployed in each experimental field. The number of soil sensors (humidity and EC, pH) ranges from 3 to 9 in the fields (three for each sector) respectively, with three different depths starting from 10 to 25 to 50 cm; however, they were installed into the positions where the WSN network could be developed in all parts of the field.

 

5. Which wireless communication technology is used to collect the data from the sensors? How is the sensing equipment powered?

Thank you, the required information is updated as recommended:

An information system for irrigation facilities management could be more efficient if it includes a wireless sensor network (WSN) that uses information and communication technologies (ICTs). We propose a wireless sensor network application for irrigation facilities management based on radio frequency identification (RFID) and quick response (QR) codes.

 

6. How often is the data collected?

The data were collected after every 30 minutes by the sensors which were then transferred to the central control unit, e.g. solar fertigation system. It is possible to collect data starting from 15 minutes.

 

7. Where is the data processed?

The data was first collected by the sensors and transferred to the central control unit through WSN, which was saved and analysed by the decision support system which further makes assessment for irrigation, fertilization and ETo for crop-based on environmental and soil parameters.

 

8. How does the fertigation system compute the ETo values from the sensor data? The models which you list only specify how to compute ETo from the weather station data.

Thank you for the opportunity to clarify. The data was first collected by the sensors and transferred to the central control unit through WSN, which was saved and analysed by the decision support system which further makes assessment for irrigation, fertilization and ETo for crop-based on environmental and soil parameters.

However, the Solar Fertigation project consists of different consortiums and experts. The manuscript of reference [24, 25] analysed the engineering and electronic aspects of the solar fertigation and IoT of the same system. Visconti et al. [24] analysed the low-cost wireless sensor network of the solar-powered fertigation system based on remotely controlled by the farmer; however, Valecce et al. [25] developed the IoT architecture of the solar fertigation system. This manuscript presents the agronomic perspectives (DSS and agronomic parameters) of solar fertigation and its potential for irrigation scheduling in crop fields. Our studies extended the work efficiency of the solar fertigation system by deep analysis of the crop and soil factors.

9. There are typesetting mistakes below l. 664 (orphaned starting and ending indices)

Thank you, we appreciate this important aspect. We just double-checked and validated the equations (13-16) and typesetting mistakes. The issue has now been corrected accordingly.

 

10. 4: labels on x axis: typesetting mistake: remove non-English characters

Thank you, we appreciate the suggestion provided. The non-English characters are now been removed accordingly.

Round 2

Reviewer 2 Report

l. 13: "This study describes the agronomic models should be integrated" - a word like "which" is missing between "models" and "should".

l. 494 grammar: describes -> describe
l. 495 grammar: shows -> show
l. 496 grammar: presents -> present
l..499 grammar: shows -> show