**1. Introduction**

One of the major global environmental issues confronting us today is climate change, which threatens our ability to meet the growing population demands for basic resources like food and water [1,2]. Due to its inherent link to natural resources, agriculture is highly sensitive to changing climatic conditions [3] and is among the most vulnerable sectors to climate change risks and impacts [4]. Changes in temperature and rainfall patterns will have direct and indirect impacts on our food systems, ranging from reduced crop production to volatility in markets and food prices [5,6]. Even though food production trends of the last 40 years have more or less kept pace with the rising food demands [7], pressure on our food systems will only intensify with changing consumption patterns, lifestyles, and diets in the coming years [1,8]. Additionally, in most developing countries, agriculture provides the main livelihood and employment opportunities for rural populations and contributes significantly to the national GDP [9]. Therefore, any reductions in production will impact agricultural economies and challenge the resilience of agricultural-dependent communities as well [9,10]. Hence, there is a need to strengthen local capacity to deal with forecasted and/or unexpected climatic changes [3], and this requires adaptation [11].

Adaptation is considered a vital component of any policy response to climate change in addition to mitigation [4], and often involves changes in processes, practices, or structures to reduce potential adverse impacts [3]. Sakschewski et al. (2014) in their assessment of agricultural production argued that production increases can be accomplished either by increasing land productivity or by increasing land resources, but since cropland expansion

**Citation:** Pathak, R.; Magliocca, N.R. Assessing the Representativeness of Irrigation Adoption Studies: A Meta-Study of Global Research. *Agriculture* **2022**, *12*, 2105. https:// doi.org/10.3390/agriculture12122105

Academic Editors: Robert J. Lascano and Alban Kuriq

Received: 26 October 2022 Accepted: 30 November 2022 Published: 8 December 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

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is limited, engineered or technological adaptive responses remain the most common in this sector [12]. One such adaptation strategy is to augment rainfed production with the use of irrigation [13]. Irrigation has the potential to buffer climate stress and increase production on existing agricultural lands, smooth production risks, and improve the growth of agricultural economies [9,13–15]. According to the UN Food and Agriculture Organization (FAO), the global area equipped for irrigation worldwide increased from 184 million ha in 1970 to 324 million ha in 2012 [16]. Much of this expansion has occurred in developing Asian countries [17], with China having the largest irrigated area in the world, followed by countries like India, the United States of America, Pakistan, and Iran in the top five [18,19].

Despite the multiple benefits, irrigation adoption among farming communities has been slow or the long-term investments needed delay its adoption [20]. This is because adoption of any technology, in general, is a complex sociological phenomenon [21] that involves a large number of factors affecting the adoption decision [21] and is seldom rapid [20]. Globally, many attempts from different disciplinary backgrounds have been made to identify the factors that act as barriers to irrigation technology adoption by farmers [22–27]. Studies from diverse geographies identify a consistent set of factors, with the cost of technology cited as the most common barrier to its adoption/uptake [28]. However, the existing literature also asserts that the determinants of irrigation adoption are often dependent on local culture, context, and/or policies [29]. For example, Alabama in the south-eastern U.S. receives an average of 55 inches of precipitation annually which allows for a long growing season in the state. However, the recent increase in flash drought instances within the state is a cause of worry for those practicing rainfed agriculture, especially the small farm owners, making them the most vulnerable to these changing climatic conditions (For more details see the U.S. Drought Monitor for Alabama from the year 2000–Present available at: https://www.drought.gov/states/alabama, accessed on 15 October 2022). Accordingly, this identification of factors influencing irrigation adoption across a wide range of geographic contexts will be useful when climate change necessitates adaptation in such unprecedented areas.

One explanation for this disconnect concerning the different factors affecting irrigation adoption, which we explore in this paper, is that the geographic contexts in which irrigation adoption studies are often conducted might be biased, and this bias has influenced the set of factors identified as having explanatory power. If such a bias exists, it would not be unique to irrigation adoption studies. For instance, Martin et al. (2012) found the global distribution and context of ecological field study sites to be biased toward more accessible locations with limited human influence. According to the authors, the geographical context of selected study sites greatly influenced the observations made within these locations [30]. Therefore, to better understand the reasons as to why a farmer chooses to adopt or not adopt irrigation, it is first essential to recognize the global extent and context-dependency of irrigation adoption. This can be achieved through a geographic representativeness analysis. Using this analytical approach, the representativeness of studies examining factors affecting the diffusion and adoption of irrigation by farmers from around the world will be assessed to determine whether the identified factors (influencing irrigation adoption) from a set of case studies selected through a systematic review were the result of certain geographic biases or not. Accordingly, to identify these potential biases, we test the following two hypotheses:

**H1.** *The geographic context of irrigation adoption studies is biased towards locations with substantial levels of existing irrigation, relatively low annual precipitation, and greater accessibility to markets.*

**H2.** *The same factors (affecting farmers' decision-making) are observed regardless of the geographic context of these studies.*

Thus, the goal of this review is to understand whether the apparent consistency of factors influencing irrigation adoption is the result of the geographic contexts in which it is studied. Given the emerging challenges presented by climate change, we suspect that there are settings in which irrigation (and the study of its adoption) is currently limited but would be beneficial (i.e., improved yields, profits). If this is the case, then the set of factors influencing the irrigation adoption process may be different than in contexts with established irrigation practices. To answer this question, we narrowed our review to articles that explicitly addressed the irrigation adoption process, rather than broader investigations of the adoption of climate-smart agriculture or best management practices, e.g., [31] or those that assessed the benefits of irrigation adoption, e.g., [32].

This paper is structured as follows. Sections 1.1–1.3 give a brief overview of the motivations behind irrigation adoption and the technological and theoretical perspectives commonly used to study the adoption process. Section 2 describes the procedure followed for this systematic review, followed by the presentation and discussion of the results of the geographic representativeness and adaptation factors' analyses in the subsequent sections and some concluding remarks.
