Achievements of Banana (Musa sp.)-Based Intercropping Systems in Improving Crop Sustainability

Abstract

Sustainable agricultural practices need to be continuously sought after so that a greater number of producers can adopt them, taking into account, above all, the food security scenario, land use efficiency, and climate change. Intercropping—a cultivation system in which two or more species are grown in close proximity in the same field—is one strategy to increase diversity in the agroecosystem. However, for intercropping systems to be adopted, their productive and economic advantages over monoculture must be clearly demonstrated. Banana (Musa sp.) growers are interested in crop diversification as a potential strategy to increase production yields and, consequently, economic income. The management of banana crops can be facilitated by intercropping, as this system plays an important role in increasing biodiversity and reducing the need for weed control in the crop rows, promoting better land use efficiency. However, this system should be evaluated alongside other indicators. Banana intercropping has significant potential and many benefits, but success depends on the interaction between the component species, appropriate management practices, and favorable environmental conditions. This review aims to provide an overview of recent studies on banana intercropping systems, focusing on the contextualization of land use, monoculture and intercropping, and evaluating intercropping indicators, as well as the benefits, risks, and disadvantages discussed in the literature, and the main outcomes of banana-based intercropping systems. The main findings relate to the possibility of using intercrops with aromatic species and the preliminary reports on the contributions of intercrops to the suppression of Fusarium wilt disease.

1. Introduction

The banana (Musa sp.) is a tropical fruit with a high economic and nutritional value. The crop occupies a prominent position in world agricultural production, as it is the most widely produced fruit globally and is grown in more than 125 countries [1], predominantly in Asia, Latin America, and Africa. India is the world’s largest banana producer, representing 26.4% of total production. China is the second largest producer, representing 9.3%, followed by Indonesia with 7.0%, and Brazil with about 5.4% of world banana production [2]. Bananas are an important food crop and trade product for many developing countries, where their role in food security and income generation has been widely recognized [3]. As one of the most popular and commonly consumed fruits in the world, bananas are appreciated for their sweet taste and soft texture. In addition, the fruit is rich in carbohydrates, vitamins, and minerals—such as potassium and magnesium, vitamin C, bioactive compounds, and resistant starch—making it highly nutritious [4,5]. Bananas are also economically and socioeconomically important, as they have a continuous production cycle and relatively rapid economic returns [6] and their cultivation provides an excellent source of income for small, medium, and large-scale producers [7].

The expansion of banana plantations can help to increase food production and, consequently, reduce food insecurity and hunger around the world [5], as well as generate employment and income throughout the production chain. Currently, there is a growing concern regarding the ecological and social implications of horticultural crops. The preservation of biodiversity and the promotion of agricultural practices that respect the environment are essential to ensuring the continuity of food production in the long term [1]. Adverse climatic environments are leading to a decline in soil fertility and an increase in the incidence of pests and diseases in banana fields, reducing crop yields [8].

Intercropping—i.e., planting two or more crops on the same land over a full or partial harvest—makes it possible to obtain a higher yield from the same or a smaller area. It is also considered a sustainable management strategy [9]. Intercropping can reduce management factors and result in sustainable systems that more effectively utilize and even potentially replenish the natural resources used during crop production in the context of the long-term management of agricultural land. Some of the benefits of intercropping for the farmer are risk minimization, effective use of available resources, efficient use of labor, increased production per unit area, erosion control, and food security [9].

The banana is a perennial crop that grows for long periods in the same fields and is predominantly grown as a monoculture [6]. In view of the vulnerability of banana monoculture to the combined effects of climate change, pests, and diseases, the diversification of cropping systems should be a recognized priority. Bananas can be intercropped with other species, both as a main and a secondary crop [10]. As the main crop, bananas can be grown in consortium with annual food crops, such as beans (Phaseolus vulgaris), maize (Zea mays), rice (Oryza sativa), and cassava (Manihot esculenta), among others, or with cover crops, which provide benefits to the soil and to the plant. As a secondary crop, bananas can be combined with perennial trees, such as coffee (Coffea arabica), the oil palm (Elaeis gineensis), cupuaçu (Theobroma grandiflorum), and cocoa (Cocos nucifera) [11]. It can also be used in diverse and sustainable agroforestry systems. Banana plants not only provide fruit of high nutritional and economic value, but also contribute to environmental benefits, such as soil conservation, microclimate regulation, and increased biodiversity [12].

This literature review aimed to provide a comprehensive discussion of recent studies discussed in the literature, focusing on the contextualization of land use, monoculture, and intercropping, as well as on evaluating intercropping in terms of metrics, benefits, risks, and disadvantages, and the main outcomes from the adoption of intercropping systems in banana plantations. The purpose is to demonstrate the application of a cultivation technology in banana plantations and provide its indicators for improving banana farming in a sustainable way.

2. Growing Bananas Sustainably Requires Changes in Land Use and Crop Management

Agriculture is one of the most important economic activities worldwide, and requires strategic planning to support social, political, and cultural development [13,14]. In addition, agriculture plays a prominent role in developing countries. However, due to population growth and the conversion of agricultural land through urbanization and industrial growth, productivity must be increased to meet the needs of a growing population [15].

Sustainable agriculture is a type of farming that uses resources more efficiently than conventional agriculture, benefits human beings, and is in balance with the environment [13]. The main approaches to implementing sustainable agriculture are the restoration of agricultural ecosystem diversity and effective management [16]. Sustainable agriculture must be ecologically sound, economically viable, and socially desirable [8].

Kaliz et al. [17] defined sustainable development as one that seeks to fulfill the needs and aspirations of the present without compromising the ability to satisfy those of the future. Sustainable development emphasizes, among other issues, the efficient use of the resources on Earth.

Changes in land use and occupation are associated with alterations to the world’s surface. Land use includes the ways in which land is utilized, including as pasture, arable land, and forest, among others. Land cover refers to the coverage of the land surface with a certain type of vegetation, bare soil, infrastructure, or water, but does not describe land use, which can differ for the same type of land cover [18]. Alterations in land use are considered fundamental to sustainable development. With rapid urbanization, rural transformation, and the development of modern agriculture, land is becoming fragmented and changes in land use threaten sustainable development [19]. The banana growing and trading system has been characterized by unequal positions of control between the international corporations that own plantations and supply the market and the farmers who grow and harvest the fruit [8].

Changes in land use must also be associated with the implementation of agricultural practices to mitigate the impact on biomes, mainly by reducing nitrogen and phosphorus loads to the environment and conserving biodiversity [20]. In view of the vulnerability of monocultures to the combined threats of climate change, pests, and diseases, the diversification of plantations must be a prioritized area. Biodiversity performance is very poor for banana producers due to its intensive monoculture production system. Climate change is increasingly threatening economic sustainability in several important producing regions, requiring responses in terms of management and cropping systems. Sustainability in banana plantations is a worldwide concern. Banana growers are interested in maintaining or increasing production gains and preserving environmental resources for the continuity of their plantations. In addition, there is a consensus that fruit produced in sustainable agricultural systems tends to have a higher market value. Similarly, banana consumers are interested in purchasing nutritious, high-quality fruit to support a healthy lifestyle.

3. Monoculture and Intercropping Systems

Monoculture refers to the cultivation of a single crop in a given area [21]. It can also refer to the practices of large-scale agriculture in which a single crop is grown over a wide area. The practice of monoculture can have a significant impact on biodiversity, as it often involves the removal of natural vegetation and the planting of large expanses of the same crop [14]. This cropping system can deplete soil nutrients, increase susceptibility to pests and diseases, and lead to a reliance on chemical inputs [22].

This practice can have negative environmental and agricultural consequences [14]. For large-scale banana farmers, intensive monoculture is easier to implement as it enables the use of machinery. However, for small-scale farmers, it is more difficult, as they have limited access to the market and to marketing information, and often grow crops for their family’s subsistence [23].

In conventional agriculture and monoculture systems, the high yield per unit area may be enough to meet the nutritional needs of growing populations in some areas; however, these systems require investments of inputs and energy that come from fossil fuels [13]. In these systems—based on conventional assessments of agricultural productivity—growth can be achieved by improving production factors, provided that the increase in output is even greater [24].

Monocultures are prevalent in most tropical countries. Bybee-Filey and Ryan [25] reported that, in Australia, landowners have adopted the broadacre system [9,26], which refers to farms using large-scale crop production. The authors emphasized that farming systems in Australia are dominated by intensive monocultures managed through crop rotation and the integration of livestock, when possible, as mixed farming enterprises. These practices are based on the economic view of specialization and economies of scale, which occur when a farmer increases the scale of production, thus distributing fixed costs over many production units and reducing the cost of production per unit [9].

Bananas are perennial crops that grow for long periods in the same fields and are predominantly grown as monocultures [6,27]. Banana monoculture is widely used in intensive agriculture [28]. The system of growing a single crop, such as bananas, repeatedly on the same piece of land was invented to increase food supply and to fight hunger. Unfortunately, its unintended consequences threaten greater global insecurity and exacerbate climate change [14].

Intercropping is an ancient farming practice [29]. Mousavi and Eskandari [13] pointed out that there is evidence that planting crops in consortium has a long history. This agricultural system consists of growing two or more crops simultaneously in the same field for all or part of the growing season [30]. It is important to note that in intercropping systems, the plants do not have to be planted at the same time; the aim is for two or more crops to grow together in one area during part of or the entire crop cycle [13,31].

Crop diversification through intercropping can improve the results and stability of agricultural production in the face of seasonal variability and climate change. Different species react differently to environmental conditions, so if one species is negatively affected by adverse weather conditions, another intercropped species can still produce a feasible yield.

Intercropping is a cultural practice in which two or more crops are grown on the same field in a year with different cropping patterns. In this multiple cropping system, biodiversity and pest suppression are enhanced. Biodiversity can restore the natural elements of the agricultural ecosystem because almost all elements favorable to the natural enemies of pests are available in a diversified agricultural ecosystem. Modern energy-intensive technology used in agriculture is one of the vital causes of biodiversity loss. With the intercropping system, enhanced biological pest control can be ensured with a higher level of crop diversity, as opposed to energy-intensive farming [30,31].

One of the biggest challenges of intercropping with two or more crops is maintaining the productivity of each crop [32]. Yet, intercropping can help achieve a higher yield than planting just one crop at a time [22]. Therefore, it is important to choose a combination of crops that grow well together in order to use environmental resources more efficiently—such as solar energy and regarding water per unit area per unit time—and to maintain soil health while improving yield [33]. Intercropping is widely practiced by small-scale farmers, as it supports their livelihood by producing a diverse range of food crops [34].

The economic logic of intercropping is based on the theory of economies of scope, which arises when a farmer can use the same inputs to produce two or more products, thus reducing the cost of producing them separately [9]. Table 1 summarizes the main characteristics of monoculture and intercropping systems.

Table 1. Summarized contextualization of monoculture and intercropping systems in banana plantations.

Monoculture	Reference	Intercropping	Reference
Single crop	[6,21,27]	Two or more crops simultaneously	[13,29]
Large scale	[23]	Small scale	[34]
Impact on biodiversity	[14]	Increased biodiversity	[30,31]
Deplete soil nutrients	[22]	Stability environmental resources	[14]
Increase susceptibility to pest and diseases	[22]	Increased pests and diseases suppression	[22]
Reliance on chemical inputs	[14]	Less reliance on chemical inputs	[14]
Negative environmental and agriculture consequences with greater impact from climate change	[14]	Stability agricultural production due to seasonal variability with less impact on climate change	[14,30,31]
Higher yield per unit area	[13]	Can achieve higher yield per unit area with two or more component crops	[22]
Specialization of economies of scale when increasing the scale of production leads to a reduction in production costs per unit	[9]	Economies of scope when the same inputs are used to produce two or more products	[9]

Table 1. Summarized contextualization of monoculture and intercropping systems in banana plantations.

Monoculture	Reference	Intercropping	Reference
Single crop	[6,21,27]	Two or more crops simultaneously	[13,29]
Large scale	[23]	Small scale	[34]
Impact on biodiversity	[14]	Increased biodiversity	[30,31]
Deplete soil nutrients	[22]	Stability environmental resources	[14]
Increase susceptibility to pest and diseases	[22]	Increased pests and diseases suppression	[22]
Reliance on chemical inputs	[14]	Less reliance on chemical inputs	[14]
Negative environmental and agriculture consequences with greater impact from climate change	[14]	Stability agricultural production due to seasonal variability with less impact on climate change	[14,30,31]
Higher yield per unit area	[13]	Can achieve higher yield per unit area with two or more component crops	[22]
Specialization of economies of scale when increasing the scale of production leads to a reduction in production costs per unit	[9]	Economies of scope when the same inputs are used to produce two or more products	[9]

4. Evaluating Intercropping Indicators

There are several indicators used to compare intercropping and monocropping systems. In most research projects, all intercropped species are also tested as monocultures, so the advantages and disadvantages of intercropping can be compared to the practice of monoculture [9].

The agronomic viability of intercropping can be evaluated using productivity and competitive indices (Table 2), including land use efficiency (LUE), the land equivalent ratio (LER), the area-time equivalent ratio (ATER), the land equivalent coefficient (LEC), the relative density coefficient (RDC), aggressivity (A), the competitive ratio (C), the system productivity index (SPI), the intercropping advantage (IA), gross income (GI), net income (NI), rate of return (RR), profit margin (PM), and actual yield loss (YL), among others (Table 2) [9,35,36]. These indices are used to not only estimate the effects of competition among different crops, but also to assess which system is most effective in managing environmental resources to provide greater productivity and sustainability [22,33].

LUE considers crop yields in intercropping and monoculture systems and relates them to land use equivalence; it is one of the most widely used indices to evaluate intercropping [31]. LER provides a rough estimate of the area of land needed to obtain the same yields as an intercropping system. ATER is an alternative index to LUE because the latter does not consider time. As such, LUE can overestimate the advantage of intercropping, especially when the crops differ significantly in crop cycle duration [22,33].

A systematic assessment of LUE needs to support decision-making in land use management and to promote its use in a better and more efficient way [37]. Lin and Hülsbergen [38] presented a new method for calculating LUE, starting with an overview of the different approaches to assessing agricultural LUE. This method takes into account the quality and function of agricultural products and the relationship between the yield of the farm assessed and the average yield of the reference region with comparable soils, climate, and socio-economic conditions. The main conclusion is that LUE should be used in combination with agri-environmental indicators to ensure efficient and sustainable land use. The methods used to quantify the effects of changes in land use are still the subject of intense research, stimulating much scientific discussion [17]. This study presents research on land use indicators in the context of land use efficiency. The overall aim is to fill the knowledge gap on responsible and sustainable land use management.

According to Ferreira and Féres [39], the relationship between property size and land use efficiency in the Brazilian Amazon was negative; the authors concluded that the current process of land concentration observed in this region would result in an increase in land use inefficiency.

The LEC is obtained from the product of the LER of each individual crop in the intercropping system, and must be at least 25% for intercropping to have a productive advantage [35].

The RDC index represents a measure of the dominance of one crop over another. The A index indicates the extent to which the relative increase in the yield of one crop is greater than that of the other crop in an intercropping system. This index measures the dominance among the intercropped species [15]. The C index represents the number of times one crop is more competitive than the other [22]. C offers an alternative to assess competition between different crops and provides a more accurate measure of the competitive capacity of the crops [40]. C represents the proportions of individual LUEs of the two component crops and considers the proportion in which they are initially planted [22].

Table 2. Competitive and productivity indicators used to assess the efficiency of intercropping in relation to monoculture.

Indicator	Formula	Criteria for Decisions	Reference
LUE	LUE = (Yai)/(Ybm) + (Ybi)/Yam)	LUE > 1 indicates a productive advantage of intercropping; LUE = 1 no productive advantage; LUE < 1 productive disadvantage	[9,22,33,35,40]
LER	LER = Yam/Ybm + Yai/Ybi	LER > 1 intercropping is most effective; LER < 1 intercropping has a negative effect on the yield	[22]
ATER	ATER = [(LUEa × ta) + (LUEb × tb)]/Tbi	ATER > 1 productive advantage; ATER = 1 no productive advantage; ATER < 1 productive disadvantage	[40]
RDC	RDC = {(Yai × Zb)/[(Yam − Yai × Za)]} × {(Ybi × Za)/[(Ybm − Ybi) × Za]}	RDC > 1 productive advantage; RDC = 1 no productive advantage; RDC < 1 productive disadvantage; RDCai > RDCbi indicates that the main crop presents strong interspecific competition	[35,40]
A	$\mathrm{A}\mathrm{a}=[\mathrm{Y}\mathrm{b}\mathrm{i}/(\mathrm{Y}\mathrm{a}\mathrm{m}\times \mathrm{Z}\mathrm{a}\left)\right]-\left[\mathrm{Y}\mathrm{b}\mathrm{i}/\left(\mathrm{Y}\mathrm{b}\mathrm{i}\times \mathrm{Z}\mathrm{b}\right)\right] \mathrm{a}\mathrm{n}\mathrm{d}$ $\mathrm{A}\mathrm{b}=[\mathrm{Y}\mathrm{b}\mathrm{i}/(\mathrm{Y}\mathrm{b}\mathrm{m}\times \mathrm{Z}\mathrm{b}\left)\right]-[\mathrm{Y}\mathrm{b}\mathrm{i}/(\mathrm{Y}\mathrm{b}\mathrm{m}\times \mathrm{Z}\mathrm{b}]$	Both crops are equally competitive when A = 0. When A is +, the culture with a + sign is dominant and the culture with a—sign is dominated	[35,40]
C	C = Cb + Cl Cb = (LUEa/LUEb) × (Za/Zb) Cb = (LUEb/LUEa) × (Zb/Za)		[22]
SPI	SPI = [(Yam/Ybm) × Ybai] + Yabi		[40]
IA	IA = AYat × Pat + AYbc × Pbt	IA > 0 intercropping advantage; IA ≤ 0 intercropping disadvantage	[36,40]
GI	CPa × Pa; CPb × Pb		[40]
NI	NI = GI − TC		[40]
RR	RR = GI/TC		[40]
PM	PM = (NI/GI) × 100%		[40]
YL	YL = (WL/WI) × 100%		[40]

LUE = land use efficiency; ATER = area-time equivalent ratio; RDC = relative density coefficient; A = aggressivity; C = competitive ratio; SPI = system productivity index; IA = intercropping advantage; GI = gross income; NI = net income; RR = rate of return; PM = profit margin; Y_ai = yield of main crop in the intercropping; Y_bi = yield of second crop in the intercropping; Y_am = yield of main crop in the monocropping; Y_bm = yield of second crop in the monocropping; t_a = duration of main crop cycle; t_b = duration of second crop cycle; t_ab = duration of the total time of intercropping system; Z_a = proportion of main crop intercropping with second crop; Z_b = proportion of the second crop intercropping with main crop; A_a = aggressivity of main crop; A_b = aggressivity of second crop; C = ratio for intercropping; C_a = ratio for intercropping main crop; C_b = ratio for intercropping second crop; AY_a = yield losses of main crop; AY_b = yield losses of second crop; P_a = price of main crop; P_b = price of second crop; WL = weight loss; WI = weight inputs.

Table 2. Competitive and productivity indicators used to assess the efficiency of intercropping in relation to monoculture.

Indicator	Formula	Criteria for Decisions	Reference
LUE	LUE = (Yai)/(Ybm) + (Ybi)/Yam)	LUE > 1 indicates a productive advantage of intercropping; LUE = 1 no productive advantage; LUE < 1 productive disadvantage	[9,22,33,35,40]
LER	LER = Yam/Ybm + Yai/Ybi	LER > 1 intercropping is most effective; LER < 1 intercropping has a negative effect on the yield	[22]
ATER	ATER = [(LUEa × ta) + (LUEb × tb)]/Tbi	ATER > 1 productive advantage; ATER = 1 no productive advantage; ATER < 1 productive disadvantage	[40]
RDC	RDC = {(Yai × Zb)/[(Yam − Yai × Za)]} × {(Ybi × Za)/[(Ybm − Ybi) × Za]}	RDC > 1 productive advantage; RDC = 1 no productive advantage; RDC < 1 productive disadvantage; RDCai > RDCbi indicates that the main crop presents strong interspecific competition	[35,40]
A	$\mathrm{A}\mathrm{a}=[\mathrm{Y}\mathrm{b}\mathrm{i}/(\mathrm{Y}\mathrm{a}\mathrm{m}\times \mathrm{Z}\mathrm{a}\left)\right]-\left[\mathrm{Y}\mathrm{b}\mathrm{i}/\left(\mathrm{Y}\mathrm{b}\mathrm{i}\times \mathrm{Z}\mathrm{b}\right)\right] \mathrm{a}\mathrm{n}\mathrm{d}$ $\mathrm{A}\mathrm{b}=[\mathrm{Y}\mathrm{b}\mathrm{i}/(\mathrm{Y}\mathrm{b}\mathrm{m}\times \mathrm{Z}\mathrm{b}\left)\right]-[\mathrm{Y}\mathrm{b}\mathrm{i}/(\mathrm{Y}\mathrm{b}\mathrm{m}\times \mathrm{Z}\mathrm{b}]$	Both crops are equally competitive when A = 0. When A is +, the culture with a + sign is dominant and the culture with a—sign is dominated	[35,40]
C	C = Cb + Cl Cb = (LUEa/LUEb) × (Za/Zb) Cb = (LUEb/LUEa) × (Zb/Za)		[22]
SPI	SPI = [(Yam/Ybm) × Ybai] + Yabi		[40]
IA	IA = AYat × Pat + AYbc × Pbt	IA > 0 intercropping advantage; IA ≤ 0 intercropping disadvantage	[36,40]
GI	CPa × Pa; CPb × Pb		[40]
NI	NI = GI − TC		[40]
RR	RR = GI/TC		[40]
PM	PM = (NI/GI) × 100%		[40]
YL	YL = (WL/WI) × 100%		[40]

LUE = land use efficiency; ATER = area-time equivalent ratio; RDC = relative density coefficient; A = aggressivity; C = competitive ratio; SPI = system productivity index; IA = intercropping advantage; GI = gross income; NI = net income; RR = rate of return; PM = profit margin; Y_ai = yield of main crop in the intercropping; Y_bi = yield of second crop in the intercropping; Y_am = yield of main crop in the monocropping; Y_bm = yield of second crop in the monocropping; t_a = duration of main crop cycle; t_b = duration of second crop cycle; t_ab = duration of the total time of intercropping system; Z_a = proportion of main crop intercropping with second crop; Z_b = proportion of the second crop intercropping with main crop; A_a = aggressivity of main crop; A_b = aggressivity of second crop; C = ratio for intercropping; C_a = ratio for intercropping main crop; C_b = ratio for intercropping second crop; AY_a = yield losses of main crop; AY_b = yield losses of second crop; P_a = price of main crop; P_b = price of second crop; WL = weight loss; WI = weight inputs.

The SPI normalizes the yield of the secondary crop in relation to the main crop [35]. IA represents the real income losses related to the prices of the intercropped species [40].

The GI is obtained by multiplying the crop yield of each component species of the intercrop by the price (P) paid to the producer in the regional market. Net income (NI) is calculated by subtracting the total costs (TC) of production for inputs and services from the GI. The RR is the ratio between the GI and the TC, which corresponds to the amount of revenue obtained in relation to that invested. The PM is obtained from the ratio between NI and GI, expressed as a percentage [40].

Khanal et al. [9] proposed the use of total economic value (TEV) generated by the cropping system (intercropping or monoculture). TEV can be classified into use values, i.e., values that people obtain from the use of services, and non-use values, i.e., values that people place on the existence of resources and the opportunity to pass them on intact to the next generation. However, the authors reinforced the idea that the main challenge is quantifying the non-use value of the benefits generated by intercropping systems.

Appropriate profitability and risk metrics need to be used when evaluating intercropping. The metrics consider all possible differences in costs and benefits between intercropping and monoculture systems [9].

Ditzler et al. [41] suggested a FarmDESIGN model to quantify the profitability, sustainability, and nutritional yield of current banana-based intercropping systems. The farms’ levels of agroecological intensification were grouped according to variables such as farm size, number of crops, cover, agroforestry, shade- and drought-tolerant species, and production constraints and orientations. The authors noted the disparities in agroecological practices and socioeconomic constraints among farmers, and that the FarmDESIGN model was a valuable tool for assessing farm performance and could help reduce costs and time-consuming trials.

An evaluation of the metrics of the banana and bean intercropping system [42] concluded that bananas appeared to be more competitive than beans in the intercropping system [42]. The yield of beans in the intercropping system was 52 percent of the yield of beans in the monocropping system, due to shading and nutritional effects. The LER of the banana and bean intercrop during the three seasons was 1.60. The results obtained by [43] showed that vigorous intercropping with climbing beans (Phaseolus coccineus) and soya (Glycine max) often reduced banana growth and yield. The greater economic efficiency in banana monocrop plots suggests that reliance on the LER alone may be insufficient to inform intercropping decisions.

The evaluation of the agronomic and economic benefits of coffee-banana intercropping has shown that this system is advantageous for NI when compared to banana or coffee monocultures [44]. Sonavane et al. [45] evaluated several scenarios related to the percentage of area allocated for banana–onion (Allium cepa) intercropping. The highest net revenue was recorded with 58% of the area allocated along the row and 60% the area allocated between the rows for intercropping.

According to Almeida et al. [6], the intercropping of banana plants with other crops is a common practice in agroforestry systems, with the aim of optimizing LUE, diversifying production, and increasing GI. The intercropping of sweet gourd (Momordica cochinchinensis), bitter gourd (Momordica charantia), red amaranth (Amaranthus cruentus), and radish (Raphanus sativus) with banana showed a lower yield when compared to banana monocropping [46]. However, their economic analysis indicated that banana intercropped with the evaluated species showed the maximum cost-benefit ratio compared to banana as a monocrop.

Siqueira et al. [47] conducted an economic analysis of ‘Conilon’ coffee intercropping with perennial forest species in Brazil and found that intercropping with banana plants was economically viable. The authors also emphasized that this type of intercropping is more efficient in terms of LUE than monoculture coffee. In addition, banana–coffee intercropping can provide food security, an important factor for family coffee growers, who can consume or sell the fruit. The intercropping of banana plants with coffee is beneficial and can increase the revenue of an area by more than 50% [48].

Intercropping banana and yacon (Smallanthus sonchifolius), considered a functional food, optimizes the use of the area and is profitable for the farmer [49]. The study’s economic analysis found that this system had a higher GI than banana monoculture due to the market value of yacon.

Dissanayake and Palihakkara [50] reported a yield percentage of a banana intercrop of 60.64% compared to monoculture, and their results can help inform sustainable LUE on oil palm plantations.

5. Intercropping Benefits

Intercropping is positioned as a potential cropping system that is environmentally friendly and can help address the challenge of increasing production with less or equivalent amounts of land, thereby improving food security [26].

Intercropping is especially advantageous when the associated crops exhibit some complementarity, which can depend on the management of the system. However, the bio-agro-economic efficiency of such systems is directly linked to crop species, production factors, spatial arrangement, and growing seasons [40]. It is therefore important to choose a combination of crops that grow well together in order to efficiently use environmental resources, as noted above, and support soil health, while also improving yield [33].

There are several benefits to adopting intercropping systems, especially for perennial crops [51] such as bananas. The main advantages include increasing or maintaining productivity and profitability, minimized losses in productivity and profitability, effective use of natural resources, weed control, pest and disease reduction, nutrients cycling, and improving nutritional management and crop resilience (Figure 1).

5.1. Increasing or Maintaining Productivity and Profitability

Banana and other fruit farmers implement crop diversification strategies for a variety of reasons, including maximizing yields [51] and supporting the establishment of a permanent intercropping system. In this case, both crops are cultivated over several years and a temporary intercrop is used to improve the economic viability of implementing a banana plantation [11]. The main reason for intercropping bananas/plantains is to obtain both additional food and a cash return, as well as to reduce the cost of establishing the plantation [27,52].

Intercropping can help achieve a higher yield than planting just one crop at a time [22,34,53]. Increased yield is important, especially for small-scale farmers and in areas where the growing season is short [13,34]. A higher yield in intercropping can be due to more effective use of resources—such as nutrients, solar radiation, and water [24]—and more effective and complementary interaction between the component species [32]. An increase in productivity can lead to greater profitability. However, extra labor, material, and financial resources were not considered in the profitability metrics.

Yogendra et al. [15] emphasized that intercropping offers a viable solution to achieve greater productivity within the constraints of limited available land and provides an increase in yield. Intercropping can reduce production costs and diversify and stabilize farm income [31].

Field research conducted at scale in Costa Rica indicated that the conventional coffee–banana intercropping system could be scaled up to achieve a productive and profitable system that produces high-quality bananas [54].

The use of aromatic species in intercropping can provide farmers with additional income, contribute to the qualitative and quantitative diagnosis of plant formations and entomofauna balance of crops, and reduce costs and environmental damage caused by the excessive use of pesticides [55]. Income generated from aromatic species can be more profitable from an economic point of view than subsistence crops often used in association with banana plantations [56]. Lemongrass (Cymbopogon citratus), which has various medicinal properties, is widely grown for commercial essential oil extraction [57]. It is commonly consumed as a tea, but also has uses in the pharmaceutical, food, cosmetics, and perfume industries [58]. Furthermore, intercropping can facilitate entry into consumer markets for crops like lemongrass, taking advantage of the demand for other, better-known crops such as bananas [30].

Oil palm is the main edible, oil-producing plant in the world, and in tropical countries it is well established as a perennial plantation crop. However, during the oil palm juvenile phase, there is almost no income for the producer, so intercropping could provide an opportunity to obtain revenue before the oil palm’s first harvest [50].

Aromatic plants are a source of essential oils, cosmetics, and biocides, and in intercropping systems they play a positive role in increasing farmers’ additional income due to the greater added commercial value of their essential oils [59].

Maintaining productivity can be considered as an advantage of the intercropping system, as it can lead to maintaining or increasing profitability. Almeida et al. [6] reported that no difference was found in banana productivity when intercropped with acai (Euterpe oleracea). Rodrigues de Jesus et al. [60] concluded that the growth and yield of banana cultivars exhibited similar performance in both monoculture and intercropping with lemongrass.

Intercropping can minimize the risk of losses for producers [30]. This is related to the fact that different component species respond differently to seasonal variations in the climate [61,62]. Consequently, if losses occur for one component, they may be compensated by the other. Minimizing productivity losses can mitigate profitability losses [63]. Production failure risk in intercropping systems is lower than in monoculture and monocropping systems [40].

5.2. Promoting the Effective Use of Natural Resources

Intercropping can help control erosion due to providing increased soil cover that reduces surface runoff [23]. In addition, intercropping can improve the physical, chemical, and biological properties of the soil [64], as well as increase the circulation and efficiency of nutrient use and the recovery of degraded areas [16]. Intercropping is proposed as a potential cropping system that is environmentally sound in the current climate change scenario, due to its ability to enhance radiation and water use efficiency [60]. Other reported benefits are an increase in organic matter, earthworm and soil microbial activity, and improvement in soil structure [59].

The components of intercrops do not compete for the same ecological niche due to morphological and physiological differences, and competition between species is less prominent than competition within species [13].

5.3. Weed Control

Intercropping, when well-managed, offers advantages over monocultures, including in weed control [31]. Intercropping is more effective than monocropping in suppressing weeds, but its effectiveness varies widely [21]. Banana–bean intercropping systems common in East Africa are characterized by low banana productivity. In these systems, the soil is manually ploughed twice a year before the beans are planted, with potentially detrimental effects on the banana plant’s shallow root system [65].

The advantages of weed control are twofold: usurping weed resources and suppressing weed growth through allelopathy [13]. Controlling weeds is one of the main reasons for establishing a banana-based intercropping system [27,52]. According to Concenço et al. [66], the shade provided by banana plants proved to be an efficient management strategy for weed suppression in the coffee–banana intercrop.

Intercropping can facilitate banana crop management by reducing the need to control weeds in the crop rows due to the cultivation of another component species in the rows [67]. Rodrigues de Jesus et al. [60] reported that the banana–lemongrass intercropping system facilitated banana crop management by reducing weed control in the crop rows.

5.4. Pest and Disease Reduction

Pests and diseases are a major risk to the sustainability of banana production, through the direct impact of agrochemicals on the environment, the loss of income that increases the area needed for production, and the associated health risks for workers in the sector. Intercropping can reduce damage from pests and disease [31]. A greater diversity of species in agricultural ecosystems can help to mitigate the spread of plant pathogens [6,13,68]. Intercropped systems provide different benefits in pest management according to two hypotheses. One is the concentration of resources hypothesis, and the other is the natural enemies hypothesis. Intercropping directly and indirectly influences the increase in biodiversity, which results in a reduction in the density of pests in crop fields. Consequently, less expenditure on the use of pesticides is required and, ultimately, a higher yield also brings some financial benefits. The intercropping system uses the plant’s inherent ability to protect against pests. Therefore, more knowledge is needed about crop genotypic diversity, plant diversity, and the plant’s ability to protect itself from pests [6,31].

Improving the microecological environment of soil for banana roots is crucial to promote the stable and sustainable development of banana farming. Intercropping banana and sweet potato (Ipomoea batatas) had a significant effect on regulating the structure and composition of the soil microbial population and improving the abundance and diversity of the microbial population [69].

With regard to pest management in banana intercropping, it was reported that the number of banana weevils (Cosmopolites sordidus Germar), was lower in banana intercropped with millet (Panicum miliaceum) [52,70]. The probable reason for this is that the root exudates from the millet, which may inhibit the presence of the weevil. Leguminous crops such as Canavalia muzzina and Tephrosia vogelli have been reported to have repellent or insecticidal properties against the banana weevil [52].

Intercropping is a useful strategy for providing food and alternative habitats for arthropods, including generalist predators. In sustainable agriculture, ants are important predators and have complex and often strong effects on pests [71]. With the aim of optimizing control of the banana weevil, Cosmopolites sordidus, Dassou et al. [71] studied maize, taro (Xanthosoma sagittifolium), and gourd (Lagenaria siceraria) as intercrops in a banana field. The effects of the intercropping on the abundance of ants and the damage caused by C. sordidus larvae to the banana stalks were assessed. Intercropping had significant effects on ant abundance, which was negatively correlated with the damage caused by C. sordidus to the ants. Intercropping in banana plantations has the potential to alter the structure of the ant community, which contributes to the control of weevils, but the effect of the intercropped plant species remains unclear.

Banana production faces significant challenges due to Fusarium wilt, a destructive disease caused by the soil-borne fungus Fusarium oxysporum f.sp. cubense [72]. Fusarium wilt in bananas is managed by planting disease-resistant cultivars, using appropriate cultural practices, biological control agents, and intercropping [73,74].

Several studies have shown that intercropping can lead to the recruitment of beneficial indigenous soil microbial taxa via root exudates, leading to increased host protection against pathogens [75].

Intercropping contributes to the suppression of Fusarium wilt disease (Fusarium oxysporum f.sp. cubense) in bananas. In one study, intercropping with Chinese chives (Allium tuberosum Rottler) showed the potential to reduce the incidence of the disease in bananas [76]. Meanwhile, Yang et al. [77] developed an approach to reduce Fusarium wilt disease by rebuilding the soil microbiome through intercropping with green manure. Intercropping bananas and green manure demonstrated the biological basis of the disease-suppressing microbiome in terms of agricultural practices and soil management [78]. Trifolium repens effectively reduced the incidence of banana wilt disease by regulating soil microorganisms and enriching beneficial bacterial and fungal microorganisms. However, it remains to be determined whether protist communities, important soil microbial components, contribute to disease suppression in intercropping management systems [77].

Ren et al. [68] also explored intercropping as a strategy to manage Fusarium wilt disease by remodeling soil protist communities. Protists are particularly important predators that feed on microbes [79] and are important consumers of bacteria and fungi in the soil food system. Thus, they affect soil microbial composition and function. They can feed selectively on microbial prey, leading to differential impacts on soil microbial communities [80]. Through this selective predation and induction of activity, protists can promote some resistant bacteria to increase pathogen-suppressive secondary metabolites [81]. Predatory protists can potentially reduce the effect of Fusarium wilt on bananas by promoting the expression of disease-suppressive secondary metabolite synthesis genes, including, for example, the non-ribosomal peptide synthetase gene in pathogen-suppressive bacteria [82].

Ren et al. [68] assessed changes in the microbiome with a focus on protists in a banana–legume consortium using Trifolium repens. Their results highlighted that predatory protists are important agents underlying disease suppression in the consortium system, which may offer new avenues to promote plant health in sustainable agriculture. These effects have been associated with intercrop-induced changes in soil microbial composition and function, as well as modulation of the microbial community composition to increase the host plant’s functional resilience and stress tolerance [68]. They also propose that predatory protists could be the advantage controller of the soil microbiome, contributing to the suppression of soil-borne diseases.

5.5. Nutrient Cycling

Intercropping systems improve both soil nutrient cycling through the activity of the microbial community and, consequently, land productivity. However, the mechanism of interactions between the soil microbiome and nutrient cycling in the perennial orchard has yet to be identified [59]. The authors reported that, in orchards intercropped with aromatic plant species, the chemical diversity of the mixed aromatic plant species led to increased diversity, complexity, and stability of the soil microbial community and, consequently, to nutrient cycling. In addition, it has been assumed that the composition and quantity of exudates from intercrops play an important role in regulating the microbial community and nutrient availability. In general, the introduction of functional plants, such as aromatic plants, can increase primary production, alter the chemical characteristics of crop residues—e.g., N and P concentrations [83]—and alter the characteristics of roots, such as nitrogen-fixing bacteria and mycorrhizal fungi [84].

Soil microbes are associated with a variety of ecosystem processes, including the decomposition of plant residues, the degradation of organic matter, and the cycling of C and N, through their interactions with plants in the soil [85]. These processes are affected by local biotic and abiotic conditions, local vegetation patterns, and their intra-species and inter-species interactions, as well as by the introduction of new plant species, which destabilize microbial communities and their function in the rhizosphere and soil due to changes in vegetation composition and the composition and decomposition of plant residues. By decomposing the soil and mediating the biogeochemical cycles of C and N, soil microbes have the ability to adapt to the composition of different resources and can thus alter their nutrient utilization efficiencies [59].

Many of the practical benefits of nutrients cycling are related to the extensive root systems of the component species of the intercrop, which contribute to the cycling of nutrients from the deep layers of the soil and the storage of carbon in the soil, thus improving the fertility and quality of the soil [86].

According to Lin and Hülsberger [38], nitrogen-use efficiency is correlated with land degradation, which damages soil health. Nitrogen losses can be useful for analyzing the effects of various factors related to soil, climate, and cropping systems. Researchers [17] have proposed an environmental indicator to assess the sustainability of farming and cropping systems based on a simple model that simulates nitrate leaching and gaseous emissions of nitrogen, NH₃, and N₂O, in a quantitative way.

5.6. Improving Nutritional Management

The main purposes of research into banana intercropping have been to improve the use of land cultivated with bananas through more intensive cropping and to increase the nutritional base of banana plantations [27].

Bananas require a large amount of nutrients [28] and are highly efficient in phytomass production [87]. The obtaining of a high banana yield requires that nutrients are in adequate quantities and proportions in the plant [28]. Mazzafera et al. [8] emphasized the importance of adequate nitrogen requirements and the need for nitrogen fertilization to guarantee the yields and profitability of intercropping systems. Maia et al. [88] evaluated the initial growth of banana trees intercropped with green manure and concluded that the Cajanus cajan and Crotalaria juncea species provided greater banana growth. Grevillea (Grevillea robusta)–banana agroforestry systems were evaluated in central Kenya, Africa, by Musongora et al. [89], who found that low soil fertility continually restricts production and that emerging technologies are needed to address this challenge.

5.7. Crop Resilience

Due to global warming, high temperatures and resulting droughts are having a particularly damaging impact worldwide [61,90]. To combat climate change, farmers must innovate through ecological intensification to increase food production, increase resilience to extreme weather events, and reduce the carbon burden of agriculture. Intercropping can strengthen and stabilize agroecosystems in the context of climate change by improving resource use efficiency, increasing soil water retention capacity, and increasing the diversity and quality of habitats for beneficial insects that ensure pollination and natural pest control [91].

Intercropping is related to climate regulation through carbon balance. It is also receiving increased global attention as a sustainable agricultural practice, as farmers strive to improve sustainability and maintain soil health.

6. Intercropping Limitations and Risks

Intercrop systems are complex, with non-uniform competition between the component species during the growth cycle. It generally leads to unequal relative yields, making them difficult to evaluate. The direct benefits of intercropping, such as increased yields and reduced inputs, can be quantified using productivity indices. However, the environmental benefits have a long-term impact on the cropping system and cannot be measured directly by competitive indices [9].

Although intercropping has numerous benefits, it also has limitations and risks, including those detailed in Figure 1.

6.1. Size of the Growing Area

Banana plantations around the world are cultivated in two different land use contexts: in the first, by the largest and most specialized growers, they are cultivated on a large scale and are predominantly monocultures, with their production sold on different markets. In the second, crops are produced by small farms and are used almost exclusively for subsistence or, when commercialized, are sold in small markets [10,42,52]. Smallholders adopt banana-based intercropping systems in East and Central Africa, where fruit production is their livelihood and contributes to food and economic security [43,92].

Intercropping is an option to better utilize cultivated areas. However, these systems increase the complexity of management and require a steep learning curve for successful management, so they are not adopted in large areas of cultivation [91].

6.2. Decreased Crop Yield

Despite numerous benefits, intercropping has yet to be widely adopted on a large scale due to perceived risks and challenges, including decreased crop yield for both or for just one of the crop components of the systems. In addition, relatively few studies document ecosystem services conferred by intercrops alongside labor costs, which are key to economic sustainability for small, medium, and large-scale farmers [91].

6.3. Appropriate Choice of Component Crops

The use of appropriate cultivars for intercropping is one of the challenges for banana growers who adopt these systems. This is because intraspecific competition tends to be greater than competition between species [52]. Competition and dominance between species in the intercropping context must be continually assessed so that the system does not lead to losses for producers [10].

6.4. Proper Fertilization and Nutritional Status

Fertilization in the intercropping system still needs to be better evaluated and requires further study [53]. The fertilizer used for the banana plantation can serve as a residual fertilizer for the other component crop. Rodrigues de Jesus et al. [60] pointed out that in the banana–lemongrass intercropping system the inputs used for fertilization were directed towards the banana crop, without the need for the selection of specific fertilizers for lemongrass. As a result, with the amount of inputs directed exclusively to banana production, the intercropping produced more per unit area than monocropping banana. Authors also reported that the inputs used for fertilization can be directed to the banana crop without the need to select specific fertilizers for lemongrass. In addition, there were no differences in the average macronutrient contents in banana leaves, both in monocropping and in intercropping with lemongrass. These results show that lemongrass did not interfere with nutrient absorption by banana plants, which indicates that the nutritional management of the bananas did not need to be modified as a result of intercropping.

However, Rao and Edmunds [27] emphasized the need for more inputs in banana-based intercropping systems. Banana and beans were grown in monocropping and intercropping systems to evaluate the effects on the nutritional requirements. Nutrient concentration levels in the foliar tissues indicated that low potassium and high manganese availability constrained intercrop bean yield, while banana yields were associated with potassium levels in the soil [42]. Investments in external inputs are crucial for a sustainable banana intercrop system [43,93].

6.5. Use of Machinery

Banana growing is affected by numerous pests and pathogens. The yellow sigatoka (Mycosphaerella musicola) and Black leaf spot—Black Sigatoka (Pseudocercospora fijiensis)—diseases, caused by fungus, are the most important diseases of banana leaves [4,7]. These diseases are controlled through frequent application of fungicides or mineral oil sprays, which requires the use of machinery [6].

Intercropping can limit the use of machinery from planting through to harvest if a component crop is planted between the crop rows. However, in intercropping with banana plants, the other component crop can be grown in the crop rows. This is the main limitation and advantage for large-scale farmers in adopting an intercropping system, as the use of machinery over large areas is necessary during crop management [54].

Furthermore, the use of machinery in banana fields is less intensive compared to other fruit crops. This is due to the frequent spraying of pests and diseases by airplane or drone on large farms. For smallholders, the use of machinery is fairly low, due to the cost of purchasing machinery [30,54].

6.6. Shade Intensity

The main risk in adopting intercropping in orchards is related to the influence of shade intensity on the growth, biomass allocation, yield, and quality of fruit trees as the main crop in the system [16]. In their study, Kishore et al. [16] emphasized that the physiological functions of plants change with the level of irradiation; therefore, limiting light intensity is vital to guarantee production.

In the case of banana cultivation, the selection of suitable crops for intercropping depends on the relevant cultivation restrictions, namely the availability of light under the banana canopy. This acts as a limiting factor for growing annual crops, with the availability of light depending on the spatial distribution of the banana plants and the density of cultivation. As the fruit ripens, the canopy becomes larger, reducing the light in the area. Therefore, to correctly use intercropping in banana plantations, a succession of short-cycle annual crops and more shade-tolerant species is recommended at the ripening stage [10].

In East and Central Africa, Ntamwira et al. [10] noted that small-scale farmers’ banana fields are often intercropped with various annual crops to optimize land use, a practice limited by the availability of light under the banana canopy. The bananas produced by small-scale farmers in the African Great Lakes region are often pruned to provide more light to shorter intercrops, reducing the overall profitability of the farm [43]. Banana–legume intercropping is important in several countries in Africa’s Great Lakes region. This practice is widely used because of the high population pressure on the land. In this region, banana leaf pruning facilitates annual legume intercropping [94].

6.7. Disposed Waste

Growing bananas generates a large amount of waste that is discarded as a result of cultural practices. The thinning of the tillers, the removal of the male inflorescence and old leaves, and the removal of the pseudostem after harvesting result in organic material returned to the soil between the rows of banana trees, which can make intercropping more complex. Although nutrient cycling in banana plantations is very important, this means that this banana crop waste needs to be disposed of in another possible manner in order to make the banana-based intercropping system feasible [52].

7. Banana Planting Design

The spacing between banana plants in the planting rows varies according to the cultivar, the location, and the level of technology used. The most commonly used spacings are 3.0 × 2.0 m and 3.0 × 2.5 m in single rows and 4.0 × 2.0 × 2.0 m and 4.0 × 2.0 × 3.0 m in double rows, which allow for better use of the land [6].

Dense banana cultivation, an agronomic practice widely used by producers, makes better use of the land, labor, and inputs while increasing productivity. However, this strategy is only recommended for farms with favorable soil and climate conditions to support full development [7]. In general, a higher plant density can reduce the mass of the bunch and the length and diameter of the fruit. Nevertheless, productivity increases due to the greater number of plants per area [6]. The competitiveness of a crop is proportional to the increase in plant density [67].

To achieve cropping system production, many farmers are increasingly using dense cultivation [6], while intercropping has been the subject of research with the aim of developing recommendations for producers. Leaf area index was linearly correlated to yield in the intercrop system, suggesting that a higher plant density may result in higher yields [42]. The relationship between planting density and the growth and development of component crops in rubber–banana intercropping systems was evaluated by Rodrigo et al. [95], who concluded that increasing the density of banana plants from one to three rows increased biomass productivity per unit area, with no adverse effect on the growth and yield of the rubber or banana component crops. The increase in the growth of intercropped rubber trees was attributed to better crop management, since farmers tend to pay more attention to intercropped crops than to single crops, due to the additional initial income they provide.

Intercropping, according to Yogendra et al. [15], allows for better utilization of the available space, since the slower initial spacing prevents competition between crops and weeds. Banana–yacon (Smallanthus sonchifolius) intercropping optimizes the use of the area, especially when yacon is planted in double rows alternating between the banana rows [49].

Bananas intercropped with coffee is common in the Democratic Republic of Congo, Africa, but it is predominantly implemented by large-scale farmers who use a wide spacing between banana plants [10]. Studies conducted at this location concluded that climbing beans, bush beans, and vegetable amaranth had reasonable yields when intercropped with new banana plantations, regardless of plant density. However, in the second annual harvest season, a decline in yield was observed with increased banana canopy formation [10].

Cocoa (Cocos nucifera) and coffee are the crops most intercropped with bananas. However, farmers who intercrop bananas and cocoa tend to reduce the density of the banana rows, eventually replacing bananas with cocoa trees [43].

8. Banana-Based Intercropping Outcomes

Diversifying banana production systems is an important strategy to improve food and nutritional security, improve ecosystem health, and strengthen the resilience of small-scale agricultural systems [10]. Banana producers are concerned about increasing the profitability and sustainability of their plantations. The main challenges identified by growers are related to adapting cropping systems to current needs to reduce losses in the production and marketing process and, above all, to improve the final product quality to increase consumption [96].

Intercropping is becoming increasingly important in areas of the world where land is increasingly scarce, such as East and Central Africa. Bananas are a staple food for millions of people in low and middle income countries. The banana export trade that supplies North America, Europe, and other wealthy nations has a history of exploitation and conflict. The price of cheap bananas has been environmental degradation, violence, and poverty. Only recently have efforts been made to address the power imbalances in this trade. Voluntary certification schemes, in addition to the implementation of different cropping systems and management, aim to address various sustainability issues, while research into biological control has accelerated plant breeding and efficient irrigation will help prepare the sector for pest, disease, and climate change risks [97].

The growing social and environmental concerns of producers and consumers has led to the establishment of changes in the banana production sector. These modifications establish a series of criteria around social, economic, and environmental sustainability, according to which producers are classified by registered certification agencies. Producers pay a fee for the certification process and receive higher prices and, potentially, market access as rewards for complying with sustainability standards [97].

Alongside clearer demonstrations of the economic viability of intercropping, banana farmers also need technical support during the adoption process to help them resolve the complexities and location-specific challenges of managing polycultures. The environmentally friendly intensification of banana plantations requires a strategic approach than simplifies production systems, which is not without its inherent risks and challenges. Banana plants can be intercropped with various species, with different aims and outcomes. The main intercropping systems with banana plants are summarized in

Table 3. Main outcomes reported in banana-based intercropping systems and a model to quantify the profitability and sustainability of current systems.

Component Crop	Outcomes	Reference
Green Manures: Cajanus cajans and Crotalaria juncea	Greater banana growth	[88]
Coffee (Coffea arabica)	Increase economic viability; advantageous for NI, better LUE efficiency, increase the revenue, high quality bananas and weed supression	[11,44,47,48,54,66]
Bean (Phaseolus vulgaris)	Bananas appeared more competitive, low banana productivity and the need for investment in external inputs	[42,43,65]
Climbing beans (Phaseolus coccineus) and soya (Glycine max)	Reduced banana growth and yield	[43]
Onion (Allium cepa)	Highest net revenue	[45]
Sweet goud (Momordica cochinchinensis), Bitter gourd (Momordica charantia), red amaranth (Amaranthus cruentus) and radish (Raphanus sativus)	Lower yield and economic analysis with maximum cost-benefit ratio	[46]
Yacon (Smallanthus sonchifolius)	Higher GI and optimizes the use of the area	[49]
Aromatic species	Additional income, reduce costs and environmental damage	[55,56,59]
Lemongrass (Cymbopogon citratus)	Entry into consumer markets, similar performance compared with monocropping, reduced weed control and without the need to select specific fertilizers for lemongrass	[30,60]
Sweet potato (Ipomoea batatas)	Regulating the structure and compositions and improving the abundance and diversity of soil microbial population	[69]
Millet (Panicum miliaceum)	Lower number of banana weevil	[52,70]
Leguminosae (Canavalia muzzina and Tephrosia vogelli)	Repellent or insecticidal properties	[52]
Maize (Zea mays), taro (Xanthosoma sagittifolium) and gourd (Lagenaria siceraria)	Alter the structure of ant community which contributes to the control of weevil (Cosmopolites sordidus)	[71]
Chinese chives (Allium tuberosum)	Potential to reduce Fusarium wilt disease	[76]
Leguminosae White clover (Trifolium repens)	Reduced the incidence of Fusarium wilt disease	[68,77,78]
Oil palm (Elaeis gineensis)	Sustainable LUE and revenue	[50]
Grevillea (Grevillea robusta)	Low soil fertility continually restricts production	[89]
Rubber (Hevea brasiliensis)	Increase in the growth of rubber	[95]
Cocoa (Cocos nucifera)	Necessity to reduce the density of banana plantation	[43]
Agroforestry systems	Optimizzing LUE, diversifying production and increasing GI	[6]
FARMdesign model	Disparity in agroecological practices and socioeconomic constraints	[41]

.

The use of intercropping in banana plantations has its benefits and drawbacks. However, there are still some questions that require further analysis, evaluation, and research results over more harvest seasons, so that the outcomes can be applied to a greater number of producers. Thus, research in this area should increase, especially considering efforts to achieve more efficient and sustainable banana plantations. The most significant results concern weed control and the potential use of intercropping with aromatic species, as well as the contribution of intercropping to suppressing the Fusarium wilt disease. Intercropping can also have an important impact on regulating the community and structure of soil bacteria and fungi and improve the diversity and abundance of soil microbes, which can act as an insect repellent or have insecticidal properties. The central element of intercropping is the use of natural resources. However, there is a long way to go before intercropping systems are more widely adopted in the predominant monoculture system due to their productive and economic advantages over banana monoculture. These indicators need to be proven in order to convince a large number of farmers.