Adoption of agroecological intensification practices in Southern Africa: A scientific review

Abstract

Many international policy and academic circles have explored the effects of climate change on household livelihood outcomes, such as food and nutrition security, household income, and household resilience. Yet, little attention has been paid to understanding how literature has framed adoption drivers of agroecological intensification practices, an area addressed in this study. This review consolidates available literature on how adoption impacts crop yields, food and nutrition security, household incomes, and poverty reduction in Southern Africa. We systematically reviewed 45 empirical studies on adoption drivers and the associated impacts on household livelihood outcomes. Variables affecting adoption of agroecological intensification practices are rainfall distribution and temperature, non-farm economic activities, status of soil fertility, market access, ownership of communication equipment, livestock ownership, age of household head, gender of the household head, household size, factors of production and wealth status. Majority of the reviewed publications found a positive correlation between the use of agroecological intensification practices and crop yield, food and nutrition security, household incomes, and poverty reduction. Thus, it is recommended that agricultural interventions are designed in a way that farmers have a sense of ownership to ensure continuity of adoption, and practices are tailored to the needs of the target population, taking into account both the mix of technologies and existing farmer resource constraints.

Keywords:

• adoption
• agroecological intensification
• livelihood outcomes
• review
• Southern Africa

PUBLIC INTEREST STATEMENT

This study reviewed literature on the adoption drivers of agroecological intensification practices and how their adoption impacts crop yields, food and nutrition security, household incomes, and poverty reduction in Southern Africa. Variables affecting adoption of agroecological intensification practices are rainfall distribution and temperature, non-farm economic activities, status of soil fertility, market access, ownership of communication equipment, livestock ownership, age of household head, gender of the household head, household size, factors of production and wealth status. It is strongly recommended that agricultural interventions are designed in a way that farmers have a sense of ownership to ensure continuity of adoption, and practices are tailored to the needs of the target population, taking into account both the mix of technologies and existing farmer resource constraints.

1. Introduction

Agriculture plays a key role in poverty reduction and socio-economic development in Sub-Saharan Africa. However, the effects of climate change and population growth threaten the livelihoods of millions of farmers in the region (Giller et al., 2021; Tufa et al., 2023). Many international policy and academic circles have explored the effects of climate change on household livelihood outcomes such as food and nutrition security, household income, household resilience, and poverty. It is commonly acknowledged that in the long run, development practitioners have to take drastic measures to reduce the impact of climate change by stepping up climate action (FAO, 2014). Due to climate change, a decline in the production of cereal crops is predicted, resulting in persistently high levels of poverty, and food and nutrition insecurity, particularly in rural areas (Michler et al., 2019). The global climate models call for action as they predict that Southern Africa (SA) will be one of the most affected regions by climate change. Although the region has relatively better rainfall compared to other regions, it is extremely exposed to climate change with variations in rainfall patterns and extreme weather events making the agricultural sector more sensitive (Lipper et al., 2014). Mitigation of the negative impacts of climate change requires policies and programmes aimed at improving smallholder farmer’s capacity to adapt and cope with extreme climatic events. These include provision of climatic information services, provision of drought tolerant seeds, and promoting crop diversification. Previous studies advocate for Agroecological intensification (AEI) practices aimed at conserving soil moisture, efficient input use, and increasing production without increasing land area under cultivation in the region (Gambart et al., 2020; Naazie et al., 2023; Wezel et al., 2015). An understanding of what drivers encourage adoption of these practices among farmers is important in achieving this ambition (Mujeyi et al., 2021; Ngoma & Mulenga, 2016; Thierfelder et al., 2016; Zulu-Mbata et al., 2016).

Agroecological intensification (AEI) gained increasing use in literature in the last two decades due to the growing importance of maintaining quality of the environment (Milder et al., 2019; Wezel & Soldat, 2009). Agroecological intensification is defined by Wezel et al. (2015) as improving agricultural performance by reducing use of external inputs while minimizing impact on the environment through integration of ecological principles into farm system management. AEI practices encompass the traditional farming methods employed with agroecological techniques such as minimal tillage, cover cropping, use of organic matter and agroforestry (Gambart et al., 2020; Naazie et al., 2023; Wezel et al., 2015). In light of the aforementioned definitions of the different intensification concepts, we focused on AEI because it is aimed at maximizing productivity by recycling of nutrients on farm while preventing depletion of natural resources and preserving soil structure (Gambart et al., 2020). Thus, AEI integrates social and cultural perspectives which distinguish the concept from the concept of sustainable intensification (SI) (Wezel et al., 2015). It involves an integrated approach to increasing productivity while maintaining the quality of natural resources by emphasizing on the ability of smallholder farmers to use integrated practices for high productivity while maintaining farm size. It is deemed useful for preserving soil structure, mitigating land degradation, and enabling the cultivation of food crops with limited resources (Harvey et al., 2014; Jhariya et al., 2021; Naazie et al., 2023; Wezel et al., 2015, 2020). Furthermore, the core principles of AEI are optimizing use of water, nutrients and energy, maintaining and enhancing soil health, recycling of nutrients, increasing biological diversity, and reducing greenhouse gas emissions (Naazie et al., 2023; Wezel et al., 2015).

Another increasingly evolving concept almost similar in terms of meaning, principles and implications is sustainable intensification (SI). As defined by, Pretty and Bharucha (2014), Sustainable intensification (SI) is a system in which crop yields are increased without converting additional land and causing negative environmental impact. This study focused on AEI because it accentuates the system approach and integrates social and cultural perspectives which distinguish the concept from sustainable intensification (Wezel et al., 2015). Agroecological intensification determines the extent to which climate smart agriculture (CSA) objectives are achieved. It is important to note that the terms “agroecological intensification”, “sustainable intensification” and “climate smart agriculture” are frequently used interchangeably in literature. Lipper and Zilberman (2018) defined CSA as innovations that increase productivity and household resilience to achieve the United Nations (UN) sustainable development goal number 1 (no poverty) and number 2 (zero hunger). To date, CSA technologies which have been receiving more attention from literature are crop rotation, minimum tillage, intercropping, mulching, use of organic material and drought tolerant maize varieties (Mujeyi et al., 2021). Conservation Agriculture (CA) is a strong pathway to climate smart agriculture and it is the most widely practiced CSA activity in Southern Africa (Michler et al., 2019; Pedzisa et al., 2015b; Thierfelder et al., 2017). Building on the above background, technologies or practices aimed at maximizing soil water use efficiency through recycling of nutrients and maintaining the quality of environment are reviewed under the banner of AEI strategies (Jhariya et al., 2021; Naazie et al., 2023; Wezel et al., 2020) Adoption rates of AEI practices are low, especially when considering full package principles (Brown et al., 2019; Mhlanga et al., 2021; Rodenburg et al., 2021). To improve the adoption rates, it requires an understanding of farmer constraints and prevailing conditions. A rise in adoption rates improves agricultural productivity and this is expected to translate into food and nutrition secure households and increased income (Lipper et al., 2014; Makate et al., 2016). This can also happen through crop diversification and livestock integration resulting in enhanced resilience and greater cereal and legume productivity (Makate et al., 2016). Crop diversification works as a strategy for climate wise agriculture, raising crop output thereby building resilience in rural smallholder farming systems.

The agricultural sector performance in Southern Africa remains low, leading to low national aggregate production, import dependence, food insecurity, and widespread poverty in rural areas (Michler et al., 2019). In response, governments and non-governmental organizations have been promoting agroecological intensification practices for more than two decades now. Thus, the goal of this paper is to review the literature on AEI practices adoption, and impact on livelihoods in Southern Africa. Little attention has been given to reviewing the literature on the impact of agroecological intensification practices on smallholder farmers’ food and nutrition security, income, and agricultural productivity. To map the evidence, 45 most recently published journals were systematically reviewed with the themes of agroecological intensification, sustainable intensification and climate-smart agriculture. This study takes the initiative to understand how literature in southern Africa has framed the drivers of AEI adoption and consolidate evidence on the relationship between agroecological intensification adoption, and crop yield, food and nutrition security, household income and poverty in Southern Africa. The paper contributes to the evolving debates on AEI in a challenging food crop production setting such as Africa. As such, evidence gathered in the paper illuminates the causal relationship between AEI adoption and smallholder farmer’s ability to get adequate food and reduce poverty.

2. Materials and methods

This section presents a concise, retrievable and a clear articulation of the literature review process. In-depth systematic literature review was conducted to address the research objectives and bring to light what needs to be done to strengthen adoption of AEI practices in southern Africa. The method is described as systematic because evidence is synthesized using a systematic search strategy (using a search string, predefined inclusion, and exclusion criteria) to inform practice and policy (Thompson et al., 2023). The evaluation of literature included a review of the most recent literature on the effects of agroecological intensification practices on crop yields, food and nutrition security, household income, and poverty. The Preferred Standards for Systematic Reviews and Meta-Analysis (PRISMA) served as the systematic review’s guiding principles. As a result, the authors created a protocol described below, outlining the key justification and procedures followed during the systematic review process. The Southern Africa region has relatively better rainfall compared to other regions, but it is extremely exposed to climate change making the agricultural sector more sensitive hence agroecological intensification is more appropriate for this region (Lipper et al., 2014). Majority of farmers in the region rely on agriculture and it is central to reducing poverty and improving food security.

2.1. Eligibility criteria

To guarantee that current evidence was compiled, the authors restricted literature searches to only recent articles (from 2015 to 2022). Peer-reviewed journals and only studies carried out in Southern Africa were included. As the researchers are proficient in English language, only articles published in English language were included. Additionally, only papers that discuss the drivers and effects of agroecological intensification practices adoption (including SI, CSA and CA) were considered. In the end, 45 published journals were reviewed. The eligibility criteria was determined using the population, indicator, comparison, outcome, and study design (PICOS) technique (Taguta et al., 2022). The search and screening procedure was further modified by the tactics discussed below.

2.2. Search strategy

From open access web databases including SCOPUS and Ageconsearch (https://ageconsearch.umn.edu/), among others, a search strategy command was created to choose relevant articles for review. These databases were chosen based on their track record for providing comprehensive coverage of publications in agricultural development and economics. By connecting two or more phrases or related concepts to one another, a Boolean logic operator was built that enables one to get more exact and correct outcomes. In this situation, the search procedure used logical connectors, primarily “AND” and “OR,” where “AND” narrows a search and “OR” broadens it. The following key terms were used to identify relevant articles for the study specifically for only Southern Africa countries:

Title/Abstract = (Agroecological intensification* OR Sustainable intensification* OR Climate smart agriculture* OR Conservation agriculture*) AND (household livelihood outcomes*OR food security*OR crop yield*OR household income*OR poverty*) AND(SA*OR Southern Africa)

2.3. Screening and selection of studies

The exclusion and inclusion criteria used was based on abstract, title, and a common procedure used in other review studies (Dukuzumuremyi et al., 2020; Thompson et al., 2023). Only articles clearly articulating issues on drivers and impact of adoption in Southern Africa were retained during the selection process. The research employed a double review process whereby a single reviewer assesses the studies for inclusion eligibility based on the abstract and title. After that the other team member (author) repeats the process independently to reinforce consistency. Additionally, other articles were identified through snowballing; this is whereby the authors identified articles from reference lists of selected articles. Where disagreements arose, exclusion or inclusion eligibility was resolved through consensus among team members (Salehi et al., 2021). The details of the document inclusion and exclusion criteria are presented in Table 1.

Table 1. Screening and selection of studies criteria

Document inclusion criteria	Document exclusion criteria
Full text available in English	Full text not available or not available in English
Addresses the goals of agroecological intensification, climate smart agriculture and conservation agriculture	Does not address any of the goals of agroecological intensification, climate smart agriculture and conservation agriculture
Emphasis on agriculture	Emphasis not on agriculture
Peer reviewed papers, technical papers, books, book chapters and policy analysis	Grey literature (e.g bulletins and newsletters)
Focus on the link between agroecological intensification practices and smallholder farmer livelihoods (i.e food security, crop yield, household income and poverty)	Does not focus on the link between agroecological intensification practices and smallholder farmer livelihoods (i.e food security, crop yield, household income and poverty)

The screening and selection process, and flow summarizing the approach used in selecting relevant literature is presented in Figure 1. In the initial stage, a total of 170 studies were reviewed from google scholar (i.e 95 from Scopus and 75 from ageconsearch). After removing duplicates, a total of 130 studies were retained. A total of 45 peer reviewed publications were finally identified and used in the systematic review. It is important to note that all the identified studies were peer reviewed.

Figure 1. Flow diagram summarising the approach used in selecting literature.

2.4. Article management, data extraction and presentation

All reviewed articles were added to the Zotero referencing style using the Zotero extension in google chrome. Zotero is a referencing management style that allows for easy and efficient reference management as well as removal of duplicate articles. All the details of selected studies (i.e. author name, year of publication, title, country of study, research objectives, theories adapted, study design, methods used, findings and key recommendations) were exported to a data extraction Excel sheet developed. Key findings were summarized and presented mostly in tables for clear visualization and interpretation. With regards to analysis, the abstract, conclusion and recommendation sections were thoroughly reviewed, key themes and emerging issues were picked and concisely summarized per each article. Again, a double data extraction process was employed where the process was independently repeated by another team member for 50% of the reviewed articles. A full article review was conducted when it deemed necessary.

2.5. Sample of reviewed studies

Following the detailed scanning and screening of peer reviewed studies presented earlier in this section. A total of 45 articles were reviewed and these studies were published between 2015 and 2022. Majority of the reviewed articles were conducted in Zimbabwe (29%),Zambia (27%) and Malawi (20%) (Figure 2). The distribution of reviewed articles helped to provide comprehensive insights on the factors affecting agroecological intensification practices in Southern Africa.

Figure 2. Number of reviewed studies by country.

3. Results and discussion

3.1. Drivers of agroecological intensification adoption

3.1.1. Farm and farmer household characteristics influencing adoption of AEI practices

In this paper, drivers of AEI practices adoption from the reviewed literature in Southern Africa are presented in Table 2. Household age, gender, education of household head, farmer experience, household labor, loan access, off farm income, livestock ownership and distance to agricultural service providers are key determinants of adoption of AEI practices (Guo et al., 2020; Murendo et al., 2016; Sakala et al., 2021). Older farmers tend to be more risk averse, which makes them less likely to adopt new innovations, in contrast to younger farmers who are more inclined to experiment with and adopt new or improved farming methods (Murendo et al., 2016). Experience matters in adoption as experienced farmers have knowledge of soil fertility enhancing practices leading to a higher probability of technology adoption (Murendo et al., 2016). However, other school of thoughts argued that experienced farmers with a higher number of cultivated plots are likely to discontinue using new practices due to shortage of labor (Pedzisa et al., 2015a). Thus, households facing labor shortages are more likely not to adopt or dis-adopt labor intensive technology such as minimum tillage and mulching (Grabowski et al., 2016). Availability of labor affects wealth position of a household and has a positive effect on household’s decision to adopt the strategies. Wealth increases farmers risk tolerance and enables investing in productive equipment. Family size, off-farm income, distance to market, and access to agricultural credit influence adoption of AEI practices (Guo et al., 2020). Grabowski et al. (2016) argued that all technologies are viewed differently by farmers due to differences in the available resources and livelihood strategies in Zambia. This is evidenced by past input programs which drove adoption and non-adoption of new interventions (Grabowski et al., 2016). As such, poor farmers under extreme risk aversion with full opportunity cost of labor are likely to benefit from AEI (Lalani et al., 2016). Thus, smallholder farmers produce different maize quantities due to differences in availability of resources, such as manure, fertilizers and pesticides (Vanlauwe et al., 2013).

Table 2. Drivers of AEI practices adoption from literature in Southern Africa

Factors	Details
Rainfall	Low seasonal rainfall Ngoma & Mulenga (2016), rainfall and temperature distribution Zulu-Mbata et al. (2016)
Off farm economic activities	Non-farm economic activities Guo et al. (2020)
Status of soil fertility	Soil fertility Mujeyi et al. (2021), status of soil fertility Brown et al. (2019)
Market access	Distance to input and product markets Mujeyi et al. (2021), access to markets Sakala et al. (2021),
Ownership of communication equipment	Ownership of communication infrastructure (Mujeyi et al., 2021)
Livestock ownership	Tropical livestock units Mujeyi et al. (2021), livestock availability Senyolo et al. (2018), livestock ownership Murendo et al. (2016), Rusinamhodzi, (2015) Ulukan et al. (2022)
Household head age	Household head age Guo et al. (2020), Sakala et al. (2021), age squared Murendo et al. (2016)
Gender of the household head	Household head gender Sakala et al. (2021)
Labour availability	Family size Grabowski et al. (2016), Guo et al. (2020), Murendo et al. (2016)
Factors of production	Labour availability Grabowski et al. (2016), Financial resources and production resources Mofya & Hichaambwa, (2018)
Group membership and social networks	Participating in farmer field school (Lalani et al. (2016), internal lending and savings group and specific farming association Lalani et al. (2016), membership in an agricultural association or group Abegunde et al. (2019), Guo et al. (2020),
Training	Training received Grabowski et al. (2016), Vuntade & Mzuza, (2022)
Wealth status	Wealth Guo et al. (2020)
Experience and experimentation with CA	Farming experience Abegunde & Obi, (2022), Murendo et al. (2016)
Access to information	Education and agricultural extension Abegunde et al. (2019), Brown et al., (2019), Guo et al. (2020), Marenya et al. (2017), Ntshangase et al. (2018), Rusere et al. (2020) access to information Taapopi et al. (2018), Thierfelder et al. (2016), access to mobile phone Murendo et al., (2016)
Farm size	Farm size Abegunde et al. (2019), Komarek et al. (2021), area cultivated Sakala et al. (2021), land fragmentation Murendo et al. (2016)
Number of CA techniques used	Number of CA practices Pedzisa et al. (2015a), Farming practices Vuntade & Mzuza, (2022)
Institutional factors	Institutional and technological factors Grabowski et al. (2016)
Drought	Drought exposure Katengeza et al. (2017)
Diseases and pests	Prevalence of pests and diseases Kassie et al. (2015)

Majority of smallholder farmers are financially constrained, limiting their capacity to adopt AEI and other good agricultural practices (Giller et al., 2021). These financial resources include cash for purchasing inputs and hiring labor. Lack of financial resources is a major impediment to using externally proposed practices despite all the perceived benefits. Full adoption of these practices requires access to financial resources through credit provision and loans for enabling access to specific technology. In South Africa, resource endowed farmers had more chances of adopting agroecological intensification practices compared to highly resource strapped households (Abegunde et al., 2019). Similar findings were revealed by Pedzisa et al. (2015b), in Zimbabwe where resource constrained farmers abandoned AEI practices when support from non-governmental organizations stopped. Moreso, under a changing climate environment typical sowing dates, organic fertilizer application rates for smallholder households vary due to resource endowment (Nezomba et al., 2018). Previous studies on the effect of livestock ownership on AEI adoption have yielded mixed results. Livestock is a form of wealth in Southern Africa, however, in Zimbabwe no difference exists regarding livestock ownership among adopters and non-adopters (Makate et al., 2019; Mango et al., 2017). Thus, livestock ownership only increases the probability of farmers to adopt AEI which elevates household income and food security status. Farmers with little or no cattle adopted minimum tillage and use of organic manure mainly from crop residue because they do not have draught animals and animal manure (Mujeyi et al., 2021). Therefore, the use of organic material is driven by cattle ownership (Murendo et al., 2016), as they have access to animal manure at the farm.

3.1.2. Farm biophysical characteristics

Agroecological setting plays a key role in the adoption of AEI systems as a coping strategy (Thierfelder et al., 2016). The biophysical factors affecting adoption of AEI are presented in Table 2. Smallholder farmers adopt AEI practices that optimize water when rainfall amount is lower. As such, drought exposure in the previous years increases the likelihood of adopting agroecological intensification practices in Southern Africa (Makate et al., 2019). Farmers with large arable land sizes adopt AEI practices mainly because they have enough land to rotate and diversify crops leaving them with residues for mulching (Abegunde et al., 2019; Komarek et al., 2021; Sakala et al., 2021). Intercropping and mulching are mainly practiced by farmers with larger land sizes which can be subdivided into smaller plots. Farmers with smaller pieces of land are risk averse hence unwilling to have experimental plots. Thus, larger farm sizes are more convenient to farmers carrying out their day to day operations (Abegunde et al., 2019; Taapopi et al., 2018). Farmers are typically engaged in AEI activities on smaller pieces of land due to land availability as shown in Table 2. In Zambia and Tanzania, land scarcity decreases the likelihood of farmers to adopt AEI technologies (Mofya & Hichaambwa, 2018; Ngoma et al., 2021; Ulukan et al., 2022). As such, land ownership enables households to adopt AEI easily as they do not have costs of land rentals (Manda et al., 2016). Additionally, land fragmentation affects the probability that a farmer will adopt AEI due to the complexity in management and other AEI practices are more implementable on continuous plots rather than fragmented plots (Murendo et al., 2016). In Zambia, the most widely used agroecological intensification practices included soil fertility management, conservation agriculture, use of organic manure, and integration of crop and livestock (Manda et al., 2016). Furthermore, adoption of AEI is stimulated by input subsidy programs both directly through subsidy and indirectly through farmers’ experiences with the performance of AEI practices under drought conditions (Katengeza et al., 2019).

3.1.3. Institutional, social, attitudes and informational factors

Other factors affecting AEI adoption are media exposure and perception of the impact of climate change (Abegunde et al., 2019). Access to mobile phone increases the likelihood of farmers adopting drought tolerant varieties in Zimbabwe (Murendo et al., 2016). As expected, institutional, social, environmental, and informational factors are the main predictors of agricultural technology adoption (Guo et al., 2020; Rusere et al., 2020). Thus, institutional environment within which AEI is promoted can strengthen or constrain the capacity of adoption among the intended beneficiaries. Moreso, farmers perceptions of AEI practices have an impact on the rate of adoption in Southern Africa. Majority of smallholder farmers rely on rain-fed agriculture hence, availability of meteorological data specifically temperature and rainfall distribution affect the likelihood of smallholders to adopt new technologies in the preceding season as they become risk averse (Rusere et al., 2020). AEI can be adopted as a coping mechanism to weather variability where risk of crop failure would have been perceived (Zulu-Mbata et al., 2016). Risk-averse farmers preferred AEI practices linked to agroecological factors and farmer resource endowments. As such, farmers with positive perceptions are likely to adopt AEI leading to an increase in crop yield in Mozambique and Swaziland (Mango et al., 2020; Ntshangase et al., 2018). Furthermore, farmers’ positive perceptions are positively correlated with higher maize yields. Provision of extension service also played a major role in the promotion of no-till CA and mulching (Ntshangase et al., 2018). Therefore, reviewed studies almost agreed on the need for a concerted effort by all stakeholders aimed at tailoring current and future AEI programs to the needs of households.

Farmers participating in farmer field schools or agricultural associations, (e.g internal lending and savings group and specific farming associations) have positive attitude towards agroecological intensification practices (Lalani et al., 2016). This happens through sharing lessons and experiences with different AEI practices. Social capital and networks, quality of extension services, government assistance during crop failure and tenure security affect adoption of AEI practices in Southern Africa (Kassie et al., 2015; Senyolo et al., 2018). However, there are mixed findings on the direction of effect. In Malawi, social networks have a positive effect on the adoption of AEI (Marenya et al., 2017). Other authors argued that social networks negatively affect the adoption of AEI practices (Vuntade & Mzuza, 2022). In Tanzania and Malawi, market access and social capital predicted AEI adoption (Kassie et al., 2015). Additionally, social capital ensures collective action which is important in achieving widespread impact. In Zimbabwe, farmer associations such as village savings and lending groups play a key role in formation of social capital through networking and mutual engagement among farmers. Some families adopted AEI practices and later abandoned them due to loss of a family member who received training, highlighting the importance of training in adoption (Grabowski et al., 2016). Lastly, the adoption of AEI continues to face micro and macro level barriers which are continuously faced across majority of these practices (Kassie et al., 2015).

3.2. Drivers of agroecological intensification adoption intensity

In the last section, authors dwelled much on adoption as a binary measure of technology use. In this section, focus is given to adoption intensity because some farmers apply technology to only part of their fields or they pick certain components within a packaged technology. As such, the idea of adoption intensity is captured due to low levels of full adoption (partial adoption) caused by the nature of technologies, physical, socio-economic, institutional and package constraints. Results in Table 2 demonstrate a positive correlation between the number of techniques utilized by farmers and productivity in Zimbabwe (Pedzisa et al., 2015b). Furthermore, productive farmers used all of the principles and produced an estimated 2.50 tons/ha of maize, as opposed to less than 1 ton/ha for those who used three or fewer strategies (Pedzisa et al., 2015b). Following the utility maximization theory, factors such as low seasonal rainfall and being exposed to AEI for more than ten years increased the adoption intensity of agroecological intensification practices (Ngoma & Mulenga, 2016). Farm level policies aimed at increasing access to agricultural extension services, credit facilities, and farmer group facilitation are critical for increasing the adoption intensity of farm innovations (Ngoma & Mulenga, 2016; Pedzisa et al., 2015b). Non-farm economic activities which supplement farm income have a positive impact on adoption intensity of agroecological intensification practices (Guo et al., 2020).

3.3. Impacts of agroecological intensification technologies on crop yield

There are conflicting findings on the impact of AEI on crop yields. The generality relates to a decrease in crop yields in the early years of adoption and an increase in crop yields overtime as shown in Table 3 (Komarek et al., 2021; Manda et al., 2018; Snapp & Fisher, 2015; Thierfelder et al., 2017, 2018). In the long run, yield increases and agroecological intensification have a profitable food output on a smaller space compared to large pieces of land, and it is a crucial issue for farmers who are land-constrained (Manda et al., 2018; Ngoma & Mulenga, 2016; Ngoma et al., 2021). This is because smallholder farmers tend to thinly spread minimum resources over large pieces of land as a way of spreading risk, however, this compromises the yields obtained from these practices. As such, intensification ensures resources are concentrated on smaller pieces of land thereby increasing yield. Adoption of drought tolerant maize varieties, in conjunction with practices such as maize-legume rotation, residue retention, and manuring increases yields and reduces risk of crop failure particularly for resource-poor farmers who cannot afford inorganic fertilizers (Manda et al., 2018).

Table 3. Studies from Southern Africa on the impact of adoption on smallholder livelihoods

Dependent variables	Positive effect	Negative effect	No effect
Food security	Mujeyi et al. (2021), Manda et al. (2018 & 2020), Mango et al. (2020), Ngoma et al. (2023), Mhlanga et al. (2021), Mofya and Hichaambwa (2018), Ulukan et al. (2022).		Mango et al. (2017)
Crop yield	Ntshangase et al. (2018), Muoni et al. (2019), Manda et al. (2018), Westengen et al. (2018), Thierfelder et al. (2017), Snapp and Fisher (2015), Komarek et al. (2021),Rusinamhodzi (2015), Ranaivoson et al. (2022), Taapopi et al. (2018), Mupangwa et al. (2017)	Mafongoya et al. (2016), Nezomba et al. (2018), Pittelkow et al. (2015)
Income and poverty	(Ward et al., 2018), Ntshangase et al. (2018), Ng’ombe et al. (2017), Thierfelder et al. (2016), Rusinamhodzi (2015)	Redeny (2018), Snapp and Fisher (2015)

An increase in the use of manure is likely to increase the yield of AEI adopters leaving these farmers with more crop residue for feeding livestock and mulching in the following season (Westengen et al., 2018). The use of organic resources, nitrogen-fixing green manure, and grain legumes reduces climate risk among smallholder farmers in rain-fed crop production systems leading to higher crop yields (Nezomba et al., 2018; Ranaivoson et al., 2022). Moreso, residue cover and seeding maize with basins produce higher (per hectare) yields than conventional tillage practices (Senyolo et al., 2018; Taapopi et al., 2018). AEI practices significantly impact farm-level maize yield and maize production costs, with the greatest effect appearing to be generated when different technologies are combined (Kassie et al., 2015). Thus, uptake of AEI practices helps in mitigating the effect of climate change among rural households. AEI adoption improved yield compared with conventional farming methods during the experimental period in Zimbabwe (Rusinamhodzi, 2015). The effect of AEI practices on yield is mediated by soil type, rainfall amount and distribution, and selected management practices which include application rates of manure and mulching. Like Lalani et al. (2016), AEI positively affects overall productivity which in turn influences household welfare outcomes. However, the magnitude of the impact is higher for mulching adopters than for drought-tolerant maize seed adopters. Awareness of the importance of AEI practices is a key component of climate-smart agriculture. Asset accumulation is a form of investment in rural areas which enables and enhances the adoption of yield improving technologies. As such, productive assets play an important role in mitigating risks of climate change and improving food security among smallholder farmers (Guo et al., 2020; Komarek et al., 2021).

3.4. Impacts of agroecological intensification practices on food and nutrition security

The reviewed literature found mixed findings on the link between adoption of agroecological practices and food and nutrition security Table 3. Adoption of AEI improved household food and nutrition security if complemented with timely access to weather-related information in Zimbabwe (Mujeyi et al., 2021). In Zimbabwe and Malawi AEI adoption did not affect food consumption scores of farmers but, in Mozambique, farmers exposed to the technologies had increased food consumption scores compared to their counterparts not exposed to those techniques (Mango et al., 2020; Manda et al., 2018) Generally, there is evidence of a pro-rich distribution of disparities in the adoption of conservation agriculture and use of organic manure, which is mostly explained by variations in household wealth, access to agricultural advisory and extension services, and area of farmland (Mango et al., 2020). In Zambia, conservation agriculture has a positive impact on food security across the different approaches applied (Manda et al., 2018). These findings were supported by Mango et al. (2020), in Mozambique, Malawi, and Zambia using the Propensity Score Matching (PSM) technique. The use of AEI practices increased cereal consumption per year from 222.18 kg to 320.95 kg (Mango et al., 2020). This clearly shows a positive impact of adoption on the consumption of a staple crop. Furthermore, adoption of AEI practices translates to increased production which in turn increases the average dietary diversity (Ngoma et al., 2023).

The main coping mechanism against food insecurity is adoption of new or improved farming methods which lead to higher adoption rates among smallholders translating to higher yields and an increase in food availability. Thus, when used in good combinations, AEI practices have the potential to alleviate food insecurity among smallholder farmers, and to a greater extent reduce poverty (Ulukan et al., 2022). Reviewed studies highlighted the need for adoption of AEI practices as a package that includes all AEI principles in order to achieve the greatest impact on food security and nutrition (Manda et al., 2018; Mujeyi et al., 2021; Thierfelder et al., 2017). Tobit model results revealed that factors affecting adoption such as the age of the household head, family size, and off-farm income had a positive effect also on the extent of households’ food insecurity in rain-fed areas (Mujeyi et al., 2021). Thus, adoption of AEI is also believed to play an intermediary role between food security and other endogenous factors.

3.5. Impacts of agroecological intensification practices on household income and poverty

In the realm of AEI, there is a consensus among reviewed studies that when used alone or in combination, all AEI practices increase crop revenue per hectare leading to an increase in household income and a reduction in poverty as shown in Table 3 (Ng’ombe et al., 2017; Ntshangase et al., 2018). The possible combinations of AEI practices with highest crop revenue per hectare are crop residue retention, minimal soil disturbance, and use of organic manure (Ntshangase et al., 2018). Promotion of AEI practices in consideration of favorable plot level and agroecological factors led to the greatest returns among rural households in Zambia (Manda et al., 2018). Similar results were established using a doubly robust treatment effect estimator which showed that increasing the intensity of adoption improved per capita consumption expenditure, reduced poverty and narrowed the poverty gap among farm households (Ng’ombe et al., 2017; Rusinamhodzi, 2015; Thierfelder et al., 2016). However, the average treatment effect of increasing adoption levels from low to high intensity differed across quantiles of per capita consumption. These findings are similar to those of other school of thoughts that believed the adoption of AEI is stimulated by input subsidies which in turn increase productivity and reduce poverty among rural households (Manda et al., 2016).

Farmers who used complementary maize varieties and crop and livestock integration together or separately saw an increase in maize productivity and farm income per hectare (Senyolo et al., 2018). Reviewed literature also show that use of multiple stress-tolerant crops increases household income and household asset accumulation. Thus, in rural areas, households invest in livestock as a form of wealth that can be liquidated easily in the event of shocks (Mujeyi et al., 2022). Other researchers confirmed the positive impact of AEI on poverty reduction in different study sites (Abegunde et al., 2019; Rusinamhodzi, 2015). Thus, a joint adoption of crop residue retention, minimum soil disturbance and use of organic fertilizers yield the highest crop revenue per hectare among all the possible combinations of AEI practices (Ng’ombe et al., 2017; Ngoma et al., 2023; Ntshangase et al., 2018). Therefore, AEI practices significantly increased total household income and income per adult in Southern African countries.

4. Conclusion and Recommendations

The paper reviewed literature on drivers of adoption and consolidated evidence on the relationship between agroecological intensification adoption and crop yield, food and nutrition security, household income, and poverty reduction in Southern Africa. Agroecological intensification is a promising sustainable agricultural system, as it mitigates the impact of climate change in Southern Africa, against the backdrop of the region expected (for several reasons) to be the most impacted by climate change. Smallholders in maize-based cropping systems place value on high yields and income, a component of the productivity domain of agroecological intensification practices. Based on the findings, rainfall distribution and temperature, non-farm economic activities, status of soil fertility, market access, ownership of communication equipment, livestock ownership, household head age, gender of the household head, household size and wealth status are major drivers of AEI adoption. Other drivers of adoption and intensity of adoption from literature include factors of production, group membership, training, experience and experimentation with AEI, access to information, number of AEI techniques used, and diseases and pests.

Reviewed publications have shown that agroecological intensification reduces the risk of crop failure thereby positively contributing to crop yields and food nutrition and security, which translates to higher income when sold. Greater household incomes are associated with an agroecological intensification package involving maize-legume rotation, residue retention, minimum tillage, and recycling of nutrients on the farm. Furthermore, a joint adoption of agroecological intensification practices yields the highest crop net revenue per hectare. The use of agroecological intensification such as manuring and mulching increases the consumption of staple crop grain yield compared to conventional farming methods. In rural areas, households invest increased income in livestock, allowing them to recycle nutrients on their farms entailing agroecological intensification principle. More so, reviewed studies agreed that promotion of AEI with the influence of household, seed and plot level could lead to the greatest returns among rural households. Based on this review, studies argued that performance of farming systems varies depending on the agroecological settings. To achieve the greatest impact, there is need for adoption of AEI practices as a package, encompassing recommended climate smart agriculture principles.

From the reviewed publications, the authors drew key recommendations to increase adoption. It is strongly recommended that agricultural interventions are designed in a way that farmers have a sense of ownership to ensure continuity of adoption, and practices are tailored to the needs of the target population, taking into account both the mix of technologies and existing farmer resource constraints. To reduce disparities in the adoption of agricultural technologies, policymakers need to enact measures that target the less affluent sections of the farming community. There is a consensus among authors of reviewed literature indicating the need of raising awareness of the importance of agroecological intensification in smallholder farming systems. Lastly, due to the importance of financial resources in adoption, financial inclusion is needed to ensure access to capital (financial resources) for purchasing inputs and hiring labor.

5. Limitations of the study

This review has the following limitations; Firstly, only English articles were considered leaving studies published in other languages. Secondly, majority of studies included in this review were cross-sectional in nature. Thirdly, the study is a qualitative study, thereby lacking support of quantitative data. Lastly, some countries may be underrepresented due to limited number of published studies on the research topic. Nonetheless, the authors believe that despite the weaknesses, this study is of greater significance in enhancing the body of knowledge on agroecological intensification.

Author contributions

All authors listed have made a substantial, direct, and intellectual contribution to the work and approved it for publication.

Acknowledgments

We gratefully acknowledge the anonymous reviewers for their valuable work which helped us to improve the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the European Union through the project RAIZ (Promoting agroecological intensification for resilience building in Zimbabwe), the IRD-ARTS and the African Economic Research Consortium (AERC). The views expressed in this article are those of the authors and do not reflect the views or policies of these institutions, while errors are the sole responsibility of the authors.

Notes on contributors

Mark Manyanga

Mark Manyanga is an Applied Economist and lecturer at the University of Zimbabwe. He is persuing a PhD in Agriculture Environment and Food Systems at the University of Zimbabwe in collaboration with UMR-SENS (Knowledge, Environment and Societies) research unit of Montpellier, France. He holds an MSc in Agricultural and Applied Economics from the University of Zimbabwe. The paper contributes to the evolving debates on agroecological intensification in an equally challenging food crops production setting such as Africa.

Tarisayi Pedzisa

Tarisai Pedzisa is an Agricultural Economist and Senior Lecturer at the University of Zimbabwe. She holds a PhD in Agricultural Economics from University of Pretoria in South Africa and an MSc in Agricultural Economics from the University of Zimbabwe.

Benjamine Hanyani-Mlambo

Benjamine Hanyani-Mlambo is an Agricultural Economist and Senior Lecturer at the University of Zimbabwe. He holds a PhD in Agricultural Economics from the University of Kwazulu-Natal in South Africa and an MSc in Agricultural Economics from the University of Zimbabwe.