**2. Materials and Methods**

In this section, the steps and techniques used to achieve the objective of this research are presented. The study is exploratory and quali-quantitative in its nature. A systematic review of the literature was accomplished to solve the research question and reach the objective. The review was based on articles indexed in the Elsevier's Scopus and ISI of Knowledge's Web of Science (WoS) databases searched on 5 July 2019, with no restriction on the date of publication. Relevant and high-impact studies were selected, taking into account the databases chosen.

Following the procedures stated by the PRISMA protocol, a bibliometric review followed by a systematic content analysis of the articles was carried out. Bibliometrics is a quantitative and statistical technique for systematically measuring production indexes that contribute to the topic in the academic environment, characterized by measuring the influence of journals, researchers, and their trends [32]. The PRISMA protocol helps researchers improve the reporting of systematic reviews or meta-analyses, since it is based on an objective question, uses detailed and clear methods, and allows for identifying, selecting, and critically evaluating the most relevant research on the studied subject [33].

The systematic review is presented in the following steps: (i) formulate the research question; (ii) define the inclusion or exclusion criteria; (iii) select and evaluate the quality of the literature included in the study; and (iv) analyze, synthesize, and disseminate the results [34]. This choice was made due to its reliability as well as the methodological rigor necessary to develop it. Likewise, its scope allows a general analysis of the articles' contents, with a clear structuring of the information found [35]. The analysis continues with two phases of operational procedures:

First phase: two search queries were used in the databases (Scopus and WoS) to retrieve a larger number of studies. The following keywords were inserted in the search engine: the first attempt started using the terms "agr\*" and "blockchain", or "block chain" and "block-chain", returning 82 articles in the Scopus database and 221 in WoS, totaling 303 studies. In the second attempt, the search was carried out with the keywords "blockchain", and a sub search inserting the term "agr\*"; it found 266 studies in Scopus, and 160 in WoS, totaling 426 articles, as shown in Figure 1. The terms were searched under "title", "abstract", and "keywords", selecting "article" as the type of document.

**Figure 1.** Search criteria and documents retrieved in Scopus and Web of Science databases.

On completing this procedure, 729 articles were found. Then, the methodology of the PRISMA protocol was applied, as shown in Figure 2.

**Figure 2.** PRISMA flowchart and selection of articles for bibliometric and systematic review.

Figure 2 shows that, of the 729 articles found in the survey, only 71 met the four steps of the protocol: identification, selection, eligibility, and inclusion. The articles that did not have agribusiness as the study objective, those that did not make their full text available on the web, and those dealing with theoretical and bibliometric works, systematic reviews and literature analyses were disregarded. However, the excluded articles contributed to a better comprehension of the subject under study, since they were reviews of blockchain. Thus, during this stage, it was required that the central theme of an article for inclusion was blockchain and agribusiness, being the selected articles on the applications of blockchain for some purpose related to agribusiness.

Second phase: frequency of articles over time, areas of knowledge, number of publications per country, institutions, and authors, as well as the word cloud, were defined as the main bibliometric indicators; objectives, methodological procedures, purposes for blockchain application, and countries where the study was developed were the most important topics for the systematic review. The analysis and discussion of the results were developed through a quali-quantitative analysis, making a systematic review of the articles by reading each of them in depth and extracting fragments of interest.
