Evaluation of Land Suitability Methods with Reference to Neglected and Underutilised Crop Species: A Scoping Review

Reviewer 1

Author's response and related revisions

This paper focuses on the evaluation of land suitability methods (with the strong focus of cropland). The topic of the study is important and necessary in the scientific community. However, the scientific value of this paper is low, lack fundamentals about land suitability methods and geospatial technologies and should be thoroughly modified. My main observation is that the authors tried to include many important segments and new technologies, but did not succeed in analysing such broad topics with the necessary quality. I suggest focusing on more attainable segments instead.

As this is a review article, I strongly suggest that you abandon the usual manuscript sections (Materials and Methods, Results and Discussion) as it does not fit the content of your manuscript. Instead, I suggest that you form your own sections based on the content; for example, you could integrate sections 2. and 3.1. into a single section.

We acknowledge the comment made by the reviewer. Upon reworking the document, we have decided to retain the sections Materials and Methods, Results and Discussion. The manuscript was designed as a scoping review and followed a systematic review type method. Based on the requirements of a systematic review, there is a need to showcase these sections.

I have a major issue with the selection method of the analysed research articles (lines 112-116). You started from the 589 articles and by removing the duplicates there were only 240 left (?!) during the time period between 1993 and 2019. This is a clear indication that the literature base (probably Google Scholar) is probably not suitable for this review. The other problem is that you used a very dubious criterion (line 114) to further reduce the number of these papers, leaving you with only 64 papers, which you further reduced to 15. I made a thorough check of these 64 papers and did not find many of the top papers that I am aware of that meet the criteria that you set (which makes your point in line 116 incorrect). Therefore, I suggest that you do an another literature search, this time using Web of Science base, that you define your search parameters and perform an analysis based on that (without manual selection based on some unclear parameters). Figure 1. consequentially should be modified.

We acknowledge the comment made by the reviewer. The method did not consider papers from web science database. Since it is the paper's main premise, we as the research team decided to redo the literature search to include Web of Science and excluded Google scholar. The majority (~60%) of the citations found only by Google Scholar come from non-journal sources: among these, we find theses and dissertations, books and book chapters, not-formally-published such as preprints and working papers and conference papers. This created a lot of “noise” in the results and as such we decided to exclude it "A scoping review approach was used to acquire and synthesise information on land suitability for crops. Previously, there were 11 review studies related to land evaluation on agriculture and environmental studies; however, few of them focused on land suitability analysis for crops [15,19,27]. In terms of literature, the review sourced information from 1993 to 2019 using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses [28] (Supplementary Information Figure 1). Literature was sourced from Scopus and Web of Science using a Boolean search approach. The following search syntax was used (("land suitability" OR "land suitability analysis" OR "land evaluation methods" OR "species distribution models" OR "habitat suitability" OR "bio-climatic models") AND (crop* OR plant* OR yield OR agriculture). The search was limit to titles, abstract and keywords. This search identified 786 and 737 articles in Scopus and Web of Science, respectively. Identified articles were exported to Mendeley® as BibTex files and duplicates were removed, leaving 876 articles. These articles were then exported to DistillerSR (Evidence Partners, Ottawa, Canada) and titles and abstracts were screened by two independent researchers based on the application of suitability methods specifically for annual food crops. We restricted the search to annual food crops as many of the priority NUS identified for mainstreaming into existing farming systems are annual food crops. We defined annual food crops as food crops that complete their life cycle, from germination to the production of seeds, within one growing season, and then senesces. In contrast, the exclusion criteria were articles that focussed on animals and invertebrates, shrubs and trees, landforms, and non-food crops. Articles assessing land suitability of a range of crops including annual food crops and shrubs and trees or non-food crops or animals and invertebrates were retained for further analysis. Following the screening, 132 abstracts remained. Where available, full-length articles downloaded and research study details included the country where the study was carried out, the study's objective, methods or model used, crop(s) studied, whether it was a NUS (Yes/No) as presented by the priority list for SSA (see Williams and Haq [8] and Mabhaudhi et al. {29]) for full list), and the thematic factors used in assessing suitability were extracted. From 131 abstracts identified, 101 full-length papers were downloaded and used in the analysis. We developed an excel spreadsheet to enter and later quantitatively assess the extracted data. We assumed no selection bias as the literature search and curatorship was done by two independent researchers."

The other major issue that you must make a clear distinction with the methods of data standardisation, calculation of criteria weights and the aggregation of these values. In table 1, there is a very unclear set of data without references, so this could not be objectively evaluated

Moreover, writing something as "FAO, Statistics" or "Sys" for the methods in land suitability assessment is far, far below the necessary level of quality.

I suggest that you focus your research on some specific objectives within the multicriteria analysis and make a clear distinction between these steps. The same is applied for Table 2, which is also structured unclearly (especially the last row).

My final large issue is with the proposal of "A hybrid land evaluation system", based on which "future studies of land evaluation must focus". Other than citing a study by Sharma et al., you made very low scientific value of proving that these new technologies are useful for land evaluation studies based on some definite criterion, and yet you state that the future studies "must" use these technologies. While these technologies are very promising in many areas of the science and practice, I do not think that this study justifies writing them as a mandatory for land evaluation as you only briefly analysed them prior to that chapter. I suggest that you instead focus on the neglected and underutilised crop species that you mentioned in the title, which could be a subject of a more thorough analysis.

We acknowledge of sythesing more information on the  hybrid land evaluation system. The following statement were added to support the importance of hybrid land evaluation system in NUS land suitability analysis, (See line 533-545)

"In recent years, NUS studies have gained momentum with a lingering question on how and where they fit in the current agricultural landscape. Land suitability analysis for agriculture is an important technique in deciding future agricultural cropping patterns, planning and activities. Consequently, land suitability is decided on the merits of the bio-physical and socio-economic properties of each unit. Most, if not all, methods reviewed in this study can be used to assess NUS's suitability in agricultural landscapes; however, each method carries some limitations. For instance, in AHP, the consistency of original datasets, biased weighting and selection criteria may result in uncertainties is final decisions. Akpoti et al. [19] indicated that the main limitation of the fuzzy logic approach is the lack of a definite method for determining the membership function. The membership functions, which are often based on expert opinion. The integration of RS-GIS, Fuzzy-logic, and Multi-Criteria Evaluation using Analytical Hierarchy Process (AHP) could provide a superior database and guide map for decision-makers considering cropland substitution in order to achieve better agricultural production. It was interesting to note that 14.8% of the articles used HLES (Ttable 3).

In the land evaluation hybrid systems, through the linkages of more than two types of models are gaining momentum in LSA [41]. The HLES can combine traditional land evaluation systems and crop models to give land suitability for crops, to formulate strategies to promote NUS in marginal lands [132]. Following attempts to combine land evaluation methods with crop modelling, newly developed hybrid methods have captured and handled multidisciplinary data sets. However, this is often not possible due to lack of data, the most important of which are climatic data, phenological information, recorded yields, primary social-economic data such as costs, availability of markets, management and agricultural inputs[8,11]. For example, Bonfante et al. [132] developed and tested a hybrid land assessment methodology to demonstrate the impact of climate change on Italy's maise varieties. Applying these methodologies to minor crops and their landraces will require some compromise in defining unknown crop growth parameters [133]. Jahanshiri et al.[133] the assessed potential of land for crop diversification using NUS at a specific location requires a practical approach that takes advantage of available data and knowledge. Hence, the use of GIS and machine learning skills has seen a drastic evolution from traditional practices involving land use planning to new land evaluation methods. The use of big data, blockchain, cloud computing, Internet of Things (IoT) and other technological advancements improves the accuracy and reliability of land suitability methods [53]. The availability of accountable and reliable free online data is expected to play a significant role in shaping up the land use planning because local datasets are not readily available in many cases".

In addition, a table from scoped was generated  to show LSA with hybrid land evaluation system.

The review identified that, there is no single method that is supreme. The application of LSA is dependend on data availability,  type of data, expertism, available software and objective of the exercise [19,72]. Although, we recommend HLES, the hybrid method did not come out as the pancea of methods but to acknowledge that a lot of research is gravitating towards them especially  for planning and monitoring purposes, especially for climate change related issues.

Line 16: One word is redundant in "exercises address", please fix it.

Thank for picking this, the word exercises was deleted

Lines 29-30 and 32-33: I do not think that this paper supports such strong statements. Please remove them.

We acknowledge the revier suggestion. We suggest that the statements are supported by the results

Lines 37-38: It might be beneficial for the readers that you insert some global projections instead.

Thank you again,  for beneficial for the readers,  adding a statement on global projections is very important. The following statement was added, "The world's population is projected to reach approximately 10.9 billion by 2021 and about two thirds of the predicted growth in population between 2020 and 2050 will take place in Africa [1]." (See line 39-41)

Line 96: I suggest replacing "best bet" with "optimal".

The "best bet is the action that is most likely to be successful" was changed to "optimal"

Line 104: Write explicitly if you used the "OR" (most likely) or "AND" operator.

The searching criteria were presented as from database

Line 522: You wrote "drones and unscrewed (???) aerial vehicles (UAVs)". You must thoroughly check some of the statement that you wrote in the paper, as they imply a lack of fundamental knowledge of the topic that you analyse

Thank you for picking this. We acknowledge the error.  We decided to use aerial vehicles (UAVs).

Lines 712, 716, 811: The authors should carefully check and correct parts of the references. The mentioned references were consequentially not available for checking during the review.

Thank you picking this. The reference, both in text and in the list were formatted to match MDPI standards.

Reviewer 1

Author's response and related revisions

The content of the article refers to Supplementary materials: in some places it is written in italic font style (e.g. page. 3, rows 113, 115, 121; Page 4, row 150), and in other places it is written in regular font style (e.g. page 4, row 137; page 10, row 338; page 11, rows 390, 404, 405).

We acknowledge the comment by the reviewer. The  Authors list has been rewritten to match Land journal. It now reads as follows "Hillary Mugiyo^1*, Vimbayi G. P. Chimonyo,¹ Mbulisi Sibanda¹, Richard Kunz², Cecelia R. Masemola¹, Albert T. Modi¹ and Tafadzwa Mabhaudhi^1,2"

It is recommended to revise and correct formulas for certain chemicals.

"CaSO₄" instead of "CaSO4"

"P₂O₅" instead of "P2O5"

"K₂O" instead of "K2O"

"CaCO₃" instead of "CaCO3"

We acknowledge the comment made by the reviewer. Throughout the tables and within the text, chemical formulas have been presented accordingly in line with nomenclature

Some terms are explained in the List of Abbreviations, but were not presented in the table (e.g. Page 6, Table 1, Page 8, Table 2: "P2O5", "K2O"; correction was suggested "P₂O₅", "K₂O")

Some notes in the article require attention and verification / correction, as appropriate.

Page 12, row 464: "(Supplementary Error! Reference source not found.)"

Page 13, row 476: "(Supplementary Error! Reference source not found.)"

The References chapter needs to be revised and corrected, according to Instructions to Authors, Land journal