Agricultural production faces complex challenges and demands at the nexus of climate change, ecosystem resilience and environmental sustainability, with increasing risks for productivity and food security (Vigani et al. 2024). Agroforestry systems are recognised in several EU and national and sub-national laws and regulations as a sustainable land-use option for achieving climate neutrality, meeting biodiversity targets and increasing resilience through their adaptive and mitigating effects (Montero-de-Oliveira et al. 2025). Agroforestry systems exist in many variants as an agricultural practice and combine woody species, non-woody crops or forage and/or livestock. Adding woody species (e.g. trees, shrubs) to agricultural fields increases the multifunctionality of landscapes with improved ecosystem functions (Veldkamp et al. 2023) and a high potential of climate change mitigation by storing carbon (Terasaki Hart et al. 2023), with potential impacts on crop yield in some cases, such as regions where strong wind limits productivity, mainly through reduced wind erosion and improved microclimate (Kort 1988). Alley-cropping (AC) (arable and perennial crops in strips of broad widths) in temperate regions could enhance the resilience of cropping systems by modifying microclimates and water balances (Jacobs et al. 2022). Despite the many advantages, various challenges remain in managing agroforestry systems, including high costs for implementation and maintenance, complexity of management, a lack of management information and knowledge and the need to increase product quality, as well as labour-intensive pest and disease control (Sollen-Norrlin et al. 2020). Digital technologies in agriculture, such as automated systems, sensor technology, Decision Support Systems and artificial intelligence, can increase productivity, improve management efficiency and support more sustainable farming systems (Gallardo and Sauer 2018, Finger et al. 2019, Finger 2023). In agroforestry systems, these technologies are increasingly recommended as sustainable solutions to address management challenges (Tranchina et al. 2024b, Pippi et al. 2025, Daniel 2025). Therefore, this conceptual study focuses on the role of UVS management in alley cropping systems, particularly with regard to system performance and management complexity. It further proposes that smart vegetation management using robotics can enable adaptive strategies to balance biodiversity conservation and agricultural productivity.

Despite the growing attention to agroforestry over the last few decades, the land area covered by agroforestry systems in many countries is still low. As an example, an analysis of the 2015 European Land Use and Land Cover Survey (LUCAS) data revealed that agroforestry was practised on only 1.6% of the agricultural land in Germany (den Herder et al. 2017).

The low adoption of agroforestry systems has been extensively analysed, with technical-agronomic barriers consistently identified as one of the key constraints. Studies highlight the lack of suitable technologies, limited mechanization options, insufficient knowledge and the absence of best practices as major obstacles (Kassie 2017, Tranchina et al. 2024a, Tranchina et al. 2024b). For example, Schaffer et al. (2024) found that the complexity of management and the lack of appropriate technologies significantly hinder adoption. Similarly, García de Jalón et al. (2017) emphasised mechanization and labour management challenges across Europe. These technical barriers, combined with high initial investments, bureaucratic hurdles and increased labour demands, contribute to the perceived risk and uncertainty of agroforestry implementation, particularly in monoculture-dominated and short-term production environments (Montero-de-Oliveira et al. 2025). Regarding the challenges of high initial investment costs and administrative barriers, it is important to note that, in recent years, the EU and its Member States have expanded funding support for agroforestry implementation (Augère-Granier 2020). Since 2023, the implementation of agroforestry systems has also gained greater legal certainty in Germany through the regulation governing CAP direct payments (GAPDZV 2022).

Within an AC, normally there is a variety of major subzones, such as trees, the (herbaceous) understory vegetation strips (UVS) near and between the trees within a row and the arable crops (Battie-Laclau et al. 2020). In addition, the crop area can be divided into two further components, including field margin, which extends directly adjacent to the UVS up to a few metres into the field and field core (Cordeau et al. 2012, Boinot et al. 2019), see Fig. 1.

The UVS is a semi-natural habitat typically dominated by perennial species and can either be sown during the establishment of a new AC (e.g. using flowering or grass mixtures) or develop spontaneously. The management of this UVS is of crucial importance, as it can lead to diverse competitive and complementary interactions above- and belowground with all other components (trees, field margin and field core) and fauna within the AC (Jose et al. 2004). Vegetation within the UVS is usually controlled by cutting, mowing or herbicides. The frequency of these practices depends on the age of the system and varies from several times a year (to limit competition with young trees) to once every few years. In addition, more attention is often paid to controlling vegetation adjacent to trees than to vegetation between trees within a row.

Ecological succession

During the implementation of the AC on a former monocropped arable field, post-agricultural vegetation development within the UVS takes place due to vegetation dynamics in natural ecosystems (ecological succession) (Niering 1987). If ecological succession is allowed to proceed without active management, spontaneous woody vegetation may establish within the UVS, which can reduce the efficiency of subsequent management (e.g. mowing) (Zaplata 2025).

Biodiversity

Agroforestry and its UVS have a positive effect on biodiversity by increasing the abundance and diversity of several taxonomic groups. This effect is largely driven by greater habitat complexity, which creates a wider range of food resources, living spaces and microclimatic conditions for organisms (Kletty et al. 2023). Without management, UVS can turn into uniform grass areas with decreasing flowering species richness, coupled with lower abundance of wild bees, honeybees and hoverflies (Albrecht et al. 2021). Some pests or pathogens have broad host ranges. Thus, higher plant diversity can maintain them as reservoirs and make their control harder (Ratnadass et al. 2011).

Reservoirs for weeds

Farmers fear that their perennial grass strips might be a source of weed infestations, which would then disperse into the crop area and could decrease the crop yield (Cordeau et al. 2011). Indeed, weeds from UVS can colonise the field margin and field core by plant spillover through different dispersal strategies (Boinot et al. 2019). However, plant spillover is mainly restricted by dominant and competitive perennial and annual species to the field margin (first 10 m distance from grass strips) with a significant effect on weed assemblage (Cordeau et al. 2011, Cordeau et al. 2012). Compared to conventional arable systems, AC systems tend to suppress annual disturbance-tolerant weeds, while favouring weeds characterised by perenniality, a creeping growth habit and late as well as short flowering periods (Staton et al. 2021), which could cause problems in no-tillage or reduced tillage systems (Boinot et al. 2020).

Habitat for pests, pathogens and natural enemies of pests

Increasing habitat complexity can lead to increased pest abundance (e.g. herbivore species) and plant damage in AC (Pumariño et al. 2015). Due to their structural elements, AC form optimal habitats with a rich dietary composition for rodent pests (e.g. common vole), whereby damage can occur on a large scale through feeding on plants and tree roots, their network of runs and girdling of trees (Jacob et al. 2014). At the same time, UVS can promote the abundance of natural enemies of pests, including predatory birds and predatory arthropods, such as spiders and carabid beetles (Boinot et al. 2020, Edo et al. 2023). Compared with simplified arable systems, UVS have higher predation rates, which can have beneficial effects for the crops (Kletty et al. 2023). The life span and fecundity of many beneficial insects, especially pollinators, are increased within a nectar and pollen-rich plant community (Norris and Kogan 2000). AC and the UVS provide overwintering habitats for beneficial insects and lead to higher spider diversity and pest control potential (Matevski et al. 2024).

Belowground competition

Trees, plants from UVS and crops compete in complex inter- and intraspecific interactions for the natural resources water and nutrients. In sandy soils and regions with low yearly precipitation (e.g. north-east German regions), crop production of cereals, potatoes and vegetables (as potential crops in AC) is limited by competition for water (Jose et al. 2004, Drastig et al. 2016). There are large zones of root competition between UVS plants, trees and arable crops up to several metres within the field margin (Battie-Laclau et al. 2020). Root competition between tree roots and crop roots within the field margin can reduce crop yield (Swieter et al. 2021), relative growth (Fernández et al. 2008), soil moisture (Inurreta-Aguirre et al. 2022) and increase tree root dominance (Sutterlütti et al. 2023) and can result in high variation of root properties of the crop root system (Siegwart et al. 2023). The rooting systems are highly variable in both horizontal and vertical gradients and are influenced by tree species and soil properties (Mulia and Dupraz 2006) and sand content, soil layer, stand age, tillage frequency and distance from the tree row (O'Connor et al. 2023), with higher root densities in light soils (Plante et al. 2014).

Physical and geomorphological challenges for UVS management

The environment of UVS poses special challenges and is not comparable to the conditions of flower strips or field edges. The UVS is characterised by various physical structures, such as stones, branch cuttings from pruning, molehills, dead vegetation (sometimes with plant heights of > 100 cm), standing and fallen wooden poles for fastenings, holes created by field mice, plough furrows and tree guards, like plastic or organic mulching (Fig. 2).

Another challenge in managing the UVS is the width of the UVS itself and the boundary between the UVS and the alley. In narrow strips (e.g. strips only 1-2 m wide), the working width or equipment width must not be too large, otherwise it will not be able to pass the trees in the stand. Additionally, in ploughed alley cropping systems, there is a plough furrow at the boundary between the UVS and the alley, with sometimes considerable differences in height (often up to 30 cm height), which poses problems in management. Due to the increase in biomass during the growing season, the vegetation of the UVS overgrows these objects, which further complicates management (Fig. 3).

Management of the UVS comprises various tasks to regulate annual and perennial vegetation between and around trees through regular mechanical weeding, spraying, cutting or mulching. Depending on site-specific conditions, system layout and the farmer’s specific goals, there is a variety of possible management options for the UVS (Table 1 and Suppl. material 1). Regular mechanical or manual mowing of the UVS has been the most commonly used method of weed control. The type and intensity of management activities, such as mowing semi-natural meadows or flower strips, are linked to plant species richness and insect diversity, respectively. In cases where the farmer's objective is to maximise agricultural biodiversity, various management activities that differ spatially and temporally can be implemented. For example, spatially differentiated mowing frequencies, delayed mowing, removal of mowed material, variable mowing heights or even curved mowing could maximise biodiversity in the UVS (Parr and Way 1988, Tälle et al. 2018, Inagaki et al. 2020, Parmentier 2023) (Table 1).

The use of automated robotic mowers could significantly reduce labour requirements by replacing time-intensive, manual and repetitive tasks. Automated robotic mowers have gained importance in recent years, especially in predictable environments (Chui et al. 2016), which has been scaled through large machinery and extensive areas (e.g. golf courses, sports fields and airfields), with commercial solutions widely available (McElroy et al. 2025). However, automation and the use of robotics for non-routine and non-standardised tasks in agriculture can also be achieved at economically feasible costs (Marinoudi et al. 2019).

In the context of an alley cropping system, we define 'smart' field robotics as systems capable of autonomously navigating within and between UVS and performing physical management and monitoring tasks. Sensor systems are needed for environment perception to detect trees and obstacles and localisation and positioning to follow a specific path (between several UVS) or perform a proper coverage of the UVS (Polanía et al. 2026) (see Figs 4, 5).

Processing sensor data using computer vision or object detection models enables detected trees to be used not only for navigation: for example, detection of areas around trees or areas with specific weed pressure would allow applying more intensive management of these areas, in a precision agriculture framework. Another advantage would be the monitoring of trees and, for example, the early detection of diseases, the determination of the optimal harvest time of fruit trees or the optimal placement of pruning cuts for higher fruit quality in fruit trees or for knot-free wood for high-value timber (Ma et al. 2021). These applications are particularly well-suited for decision-support systems, as they not only optimise management practices, such as harvest timing and pruning, but also enable the early detection of potential problems, supporting data-driven tree management (Fig. 6).

In addition, the robot’s repeated traversal of UVS enables terrestrial biodiversity monitoring. Equipped with sensors capable of detecting target organisms, experts see great potential for tracking species abundance and community composition in the future (Pringle et al. 2025).

Challenges in the development and deployment of agricultural robots in AC systems arise from the highly variable spatial-temporal conditions within systems (see 'Physical and geomorphological challenges for UVS management') as well as between different alley cropping sites, which vary widely in tree species and varieties, age, spacing and management history. This environmental heterogeneity limits the applicability of universal software and hardware solutions and, instead, requires system-specific calibration and the generation of tailored training datasets. In addition, reliable operation (e.g. hoeing around tree bases) requires high spatial precision to avoid mechanical damage to young trees, which increases technical complexity and associated costs. At the same time, this raises questions about economic feasibility, as UVS typically occupy only a small proportion within the arable field (often 2–40%). Consequently, the development and deployment of robotic systems within AC systems must balance accuracy, adaptability and cost-effectiveness, especially when considering whether dedicated machines for UVS management are viable within whole-farm operations.

UVS is a central, but often underestimated component of AC. It strongly influences performance, ecological processes and management complexity through its impacts on biodiversity, weed dynamics, pest and pathogen interactions, as well as above- and belowground competition for resources. Despite its benefits, the UVS can amplify management challenges. In addition, labour intensity and mechanization constraints are the key barriers to wider adoption of this system. These conditions highlight the need for novel and adaptive management strategies. As a new option, smart management methods, based on digital technologies and field robotics, may provide new opportunities for addressing those challenges. For example, a management strategy using automated monitoring could help to optimise mowing regimes, improve the monitoring of tree health and pest dynamics and manage vegetation within the strips. In addition, the suggested strategy could reduce labour requirements and improve the efficiency of management operations.