1 Introduction

Sweet potato (Ipomoea batatas (L.) Lam.) is a versatile and globally significant crop, ranking as the sixth most important food crop worldwide (Escobar-Puentes et al., 2022). Its adaptability to various environmental conditions and its rich nutritional profile make it a valuable agricultural commodity. In particular, sweet potato has shown potential in suppressing invasive plant species, which is crucial for maintaining agricultural sustainability and ecosystem health (Shen et al., 2015). The crop's competitive growth characteristics and ability to thrive in diverse soil conditions have been highlighted in several studies, demonstrating its utility in integrated weed management strategies (Shen et al., 2019; Shen et al., 2023).

Despite the recognized benefits of sweet potato cultivation, there are significant challenges associated with its agronomy and mechanization, especially in hilly regions. These areas often present unique obstacles such as soil erosion, limited mechanization options, and varying microclimates. Despite these challenges, sweet potato remains a crucial crop due to its adaptability and nutritional value, making it an essential component of agricultural systems in these areas (Sapakhova et al., 2023). The cultivation of sweet potatoes in such regions requires innovative approaches to overcome the inherent difficulties and optimize production (Da Silva et al., 2023).

This study reviews the latest advances in agricultural and mechanized cultivation of sweet potatoes, with a focus on hilly areas, seeking innovative practices and technologies that can overcome specific challenges in these fields, providing actionable insights for farmers, agronomists, and policy makers, and ultimately contributing to a more sustainable and efficient sweet potato planting system. The aim is to provide information for broader agricultural and ecological management practices by understanding the competitive advantages of sweet potatoes in suppressing invasive species.

2 The Challenges of Sweet Potato Cultivation in Hilly Areas

2.1 Limitations of terrain and climate factors

Sweet potato cultivation in hilly regions faces significant challenges due to the complex terrain and climate conditions. The steep slopes and uneven land make mechanization difficult, leading to labor-intensive farming practices (Hu et al., 2012). Additionally, these areas are prone to hydrogeological instability, such as soil erosion and landslides, exacerbated by heavy rainfall and climate change (Tarolli and Straffelini, 2020). The lack of flat, arable land further complicates the use of machinery and efficient farming techniques, making it challenging to maintain consistent crop yields (Chapagain and Raizada, 2017). For example, Longquan Sheyuan Agricultural Comprehensive Development Co., Ltd. has over 800 mu (approximately 1 000 hectares) of planting bases. However, due to the terrain conditions in the area, terraced farming has become a major feature of local agricultural production (Figure 1).

Figure 1 Sweet potato planting plots in Longquan City (Photo by Xiaowei Wang)

2.2 Soil conditions and fertility management

Soil conditions in hilly regions often present another set of challenges. The soils are typically less fertile and more prone to erosion, which can lead to nutrient depletion. Managing soil fertility is crucial for sweet potato cultivation, as the crop has high nutrient demands, particularly for potassium (Navarro et al., 2020). Innovative fertilization methods, such as the use of anaerobic digestion residues (ADRs), have shown promise in improving soil fertility and crop yields. ADRs can partially or completely substitute mineral fertilizers, enhancing nitrogen agronomic efficiency and promoting better growth (Nicoletto et al., 2017). Additionally, the use of compost and biochar has been found to stimulate soil biological activities and improve nutrient cycling, which is essential for maintaining soil health in these challenging environments.

2.3 Constraints on labor resources and mechanization level

Labor resources in hilly regions are often limited, and the physical demands of farming on steep slopes can be prohibitive. Mechanization offers a potential solution to these labor constraints, but the adoption of mechanized farming practices is hindered by the difficult terrain (Hu et al., 2011). The development of specialized machinery, such as self-propelled crawlers and potato harvesters designed for hilly areas, can help mitigate these challenges by improving efficiency and reducing labor intensity (Zhou et al., 2021). However, the high cost of such machinery and the need for technical expertise to operate and maintain it remain significant barriers (Hamid et al., 2010). Additionally, the small and fragmented land plots typical of hilly regions further complicate the implementation of large-scale mechanization.

3 Progress in Agronomy of Sweet Potato Planting

3.1 Variety improvement and optimization

Variety improvement and optimization are crucial for enhancing sweet potato yields, especially in hilly regions where environmental conditions can be challenging. Breeding programs have focused on developing drought-tolerant varieties that can withstand osmotic stress, which negatively impacts productivity by inducing several morphological, physiological, and biochemical changes in the plants. These programs aim to select and improve genotypes that combine drought tolerance with high yields, utilizing physiological, metabolic, and genetic modifications as indicators for choosing suitable varieties (Sapakhova et al., 2023; Hong and Huang, 2024). Additionally, participatory research has shown that using high-yield varieties combined with proper training on planting techniques can significantly increase sweet potato yields, as demonstrated in the Philippines where yields doubled with the implementation of these strategies (Mustacisa-Lacaba et al., 2023).

3.2 Integrated management of water and fertilizer

Effective water and fertilizer management is essential for optimizing sweet potato production. Integrated nutrient management practices, such as combining synthetic fertilizers with organic sources like farmyard manure (FYM), have shown significant improvements in growth and yield attributes. For instance, applying 75% of the recommended dose of synthetic fertilizers along with 25% of nitrogen from FYM resulted in the highest productivity and net returns in rainfed potato cultivation in the northeastern hill region of India (Yadav et al., 2017). Similarly, the use of soil amendments like compost and biochar has been found to enhance soil biological activities and nutrient cycling, which are critical for maintaining soil health and supporting sweet potato growth in subtropical semiarid regions (Navarro et al., 2020). Moreover, the development of machinery that integrates fertilizing with other field operations, such as the 3-in-1 disc ridger, can improve efficiency and reduce labor costs while ensuring optimal fertilizer application (Abdullah et al., 2020).

3.3 Soil improvement and protection measures

Soil improvement and protection measures are vital for sustaining sweet potato cultivation in hilly regions. The use of organic fertilizers, such as commercial organic fertilizer, sheep manure, and mushroom residue, has been shown to significantly increase soil organic matter content, which is a key indicator of soil quality. These amendments also enhance the availability of essential nutrients like phosphate, nitrogen, and potassium, thereby improving the overall fertility of newly reclaimed lands (Li et al., 2022). Additionally, soil amendments can positively influence the microbial community, promoting a healthier rhizosphere environment for sweet potato growth. In regions with poor soil conditions, such as the hills of China, adopting appropriate soil management practices, including the use of organic fertilizers and soil amendments, can mitigate the adverse effects of complex terrain and poor soil quality on sweet potato production (Hu et al., 2012).

4 Progress in Mechanization of Sweet Potato Planting

4.1 Mechanized planting and harvesting

Mechanized planting and harvesting of sweet potatoes have seen significant advancements, particularly in regions with challenging terrains such as hilly areas. The development of specialized machinery, such as the disc ridger, has been pivotal. This implement not only forms planting ridges but also serves as an inter-row cultivator for weeding and fertilizing, significantly reducing labor costs and increasing efficiency (Abdullah et al., 2020). Additionally, the introduction of combined harvesters and segment harvesters has improved the efficiency of sweet potato harvesting, especially in hilly regions where traditional methods are less effective (Hu et al., 2012). Longquan Sheyuan Agricultural Comprehensive Development Co., Ltd. is equipped with a complete set of mechanized sweet potato planting equipment. This type of equipment is widely used in hilly areas and significantly reduces the manpower input in the sweet potato planting process (Figure 2).

Figure 2 Mechanized sweet potato planting equipment. A: Trencher; B: Fertilizer spreader; C: Vine cutter; D: Sweet potato harvester (Photod by Renxiang Cai)

4.2 Mechanization of tillage and fertilization

Mechanization of tillage and fertilization has also progressed, with innovations aimed at improving soil conditions and crop yields. The use of combined tillage units that perform deep cultivation and harrowing in a single pass has been shown to enhance soil aeration and reduce compaction, which is crucial for sweet potato growth (Salimzyanov et al., 2020). Furthermore, the integration of granular fertilizer applicators with tillage equipment ensures precise and efficient fertilization, aligning with agronomic recommendations and improving crop yields. The use of anaerobic digestion residues (ADRs) as a fertilizer has also been explored, offering an environmentally friendly alternative to traditional mineral fertilizers and demonstrating significant agronomic benefits (Nicoletto et al., 2017).

4.3 Intelligent and unmanned operation technology

The adoption of intelligent and unmanned operation technologies is an emerging trend in the mechanization of sweet potato cultivation. These technologies include the use of GPS-guided tractors and automated planting and harvesting systems, which enhance precision and reduce the need for manual labor (Figure 3). The development of intelligent machinery that can adapt to varying field conditions and optimize operations in real-time is particularly beneficial in hilly regions where terrain variability poses significant challenges (Hu et al., 2011; Pryshlyak and Mizyuk, 2021). The integration of these technologies with existing mechanized systems promises to further improve the efficiency and sustainability of sweet potato cultivation.

Figure 3 Mechanized production of SP (Louisiana Sweet Potato Farmers, USA).  Machine-assisted planting (a) and production management (b) (Adopted from Peter and Michael, 2023)

5 Case Study: Sweet Potato Planting Model in the Southeast Coastal Hilly Region

5.1 Case analysis of sweet potato cultivation in southern Zhejiang Province

Southern Zhejiang Province, characterized by its hilly terrain and complex soil conditions, presents unique challenges for sweet potato cultivation. The mechanization of sweet potato production in such regions is hindered by small plots, poor soil conditions, and decentralized farming practices (Hu et al., 2012). Despite these challenges, innovative mechanization techniques have been explored to enhance productivity. For instance, the integration of agricultural machinery with agronomic practices, such as selecting and breeding new varieties suitable for mechanical operations, has shown promise (Hu et al., 2011). Additionally, the development of specialized equipment for ridge planting and harvesting has been crucial in adapting to the hilly landscape (Figure 4).

Figure 4 Three designed treatments in this experiment: (a) RB1, finger-clip compound transplanter working under mulched raised beds system; (b) RB2, finger-clip compound transplanter working under bare raised beds system; (c) RB3, clamping-plate compound transplanter working under bare raised beds system (Adopted from Li et al., 2023a)

5.2 Innovative sweet potato planting cooperation model

In response to the challenges faced by individual farmers, cooperative models have been established to pool resources and share knowledge. One successful example is the mechanized planting pattern of Xushu27 sweet potato in Jiangsu Province, which has been widely adopted in various regions, including Suqian, Jining, Zhoukou, and Bozhou (Wang et al., 2012). This model involves coordinated efforts in nursery management, planting, harvesting, and storage, leading to significant economic benefits. By adopting similar cooperative models, farmers in the hilly regions of southern Zhejiang can achieve higher yields and better economic returns. The integration of mechanized planting with innovative cropping patterns, such as the novel triple cropping system, has also been shown to improve economic efficiency and sustainability in hilly areas (Li et al., 2023b).

5.3 The role of government policies and technology promotion

Government policies and technology promotion play a pivotal role in advancing sweet potato cultivation in hilly regions. Policies that support research and development, as well as the dissemination of mechanization technologies, are essential. For instance, the promotion of plastic film mulching has been effective in improving yield and water use efficiency in potato cultivation in Northwest China, and similar techniques could be adapted for sweet potatoes in southern Zhejiang (Xu et al., 2023). Additionally, government subsidies and incentives for adopting innovative cropping systems, such as the novel triple cropping system, can enhance the economic viability and sustainability of sweet potato farming. The role of government in facilitating access to advanced machinery and providing training for farmers is also critical in overcoming the mechanization challenges in hilly terrains.

6 Comprehensive Discussion: Prospects and Strategies for the Integration of Agronomy and Mechanization in Sweet Potato Planting

6.1 The necessity of synergy between agronomy and mechanization

The integration of agronomy and mechanization is crucial for enhancing the efficiency and productivity of sweet potato cultivation, particularly in hilly regions. Mechanization addresses labor shortages and reduces the physical burden on farmers, while agronomic practices ensure optimal growth conditions and yield. For instance, the development of machinery such as the 3-in-1 disc ridger, which combines bed making, fertilizing, and mechanical weeding, exemplifies how mechanization can streamline multiple agronomic tasks, thereby improving overall efficiency and reducing costs (Abdullah et al., 2020). Additionally, the adaptation of mechanization to the specific needs of sweet potato cultivation, such as the development of ridge-forming equipment, is essential for maximizing yield and ensuring the sustainability of farming practices (Hu et al., 2011).

6.2 Cost benefit analysis

The cost-benefit analysis of integrating agronomy and mechanization in sweet potato cultivation reveals significant economic advantages. Mechanization reduces labor costs and increases productivity, which can lead to higher net incomes for farmers. For example, the use of advanced machinery for ridge formation and inter-row cultivation has been shown to enhance yield and reduce labor requirements, resulting in substantial cost savings. Furthermore, the implementation of mechanized systems tailored to the specific conditions of hilly regions can mitigate the challenges posed by small plots and complex terrain, thereby improving the economic viability of sweet potato farming in these areas (Hu et al., 2012). The economic benefits are further supported by studies demonstrating that improved agronomic practices, such as optimized planting densities and fertilization regimes, can significantly increase yields and profitability (Shaheenuzzamn et al., 2014; Markos and Loha, 2016).

6.3 Technological pathways for sustainable development

Technological advancements play a pivotal role in the sustainable development of sweet potato cultivation. The integration of mechanization with agronomic practices can lead to more sustainable farming systems by enhancing resource use efficiency and reducing environmental impacts. For instance, the use of anaerobic digestion residues (ADRs) as a fertilizer alternative to traditional mineral fertilizers not only improves soil health but also reduces the reliance on chemical inputs, promoting sustainable agriculture (Nicoletto et al., 2017). Additionally, the development of drought-tolerant sweet potato varieties through traditional and molecular breeding methods can enhance resilience to climate change, ensuring stable yields under adverse conditions (Sapakhova et al., 2023). The adoption of automated systems, such as vertical farming with controlled environmental conditions, further exemplifies how technology can optimize growth conditions and reduce the environmental footprint of sweet potato cultivation (Rumiantsev et al., 2023). These technological pathways, when combined with sound agronomic practices, can significantly contribute to the sustainable development of sweet potato farming in hilly regions.

7 Conclusion and Prospect

The advancements in agronomy and mechanization for sweet potato cultivation in hilly regions have shown significant progress, addressing various challenges and introducing innovative solutions. Mechanization has been identified as a crucial factor in improving the efficiency and productivity of sweet potato farming. The development of specialized machinery, such as the 3 In 1 Disc Ridger, has facilitated essential activities like ridge forming, fertilizing, and mechanical weeding, thereby reducing labor costs and increasing yields. Additionally, the integration of anaerobic digestion residues (ADRs) as a fertilization method has demonstrated potential in enhancing sweet potato growth and yield, offering an alternative to traditional mineral fertilizers.

Despite these advancements, several challenges remain, particularly in hilly regions with complex terrains and poor soil conditions. The mechanization of sweet potato production in these areas faces constraints due to small plot sizes, diverse cropping systems, and decentralized farming practices. However, the proposed development models and countermeasures tailored to specific community, economic, and natural conditions provide a roadmap for overcoming these obstacles.

Future research should focus on further refining and adapting mechanization technologies to suit the unique conditions of hilly regions. This includes the development of more versatile and efficient machinery that can operate on varied slopes and terrains. Additionally, breeding programs aimed at developing sweet potato varieties that are more compatible with mechanical operations and resilient to environmental stresses should be prioritized.

The use of ADRs as a sustainable fertilization method warrants further investigation to optimize its application and maximize its benefits. Research should explore the long-term effects of ADRs on soil health and crop productivity, as well as the economic feasibility of large-scale implementation. Moreover, the potential of integrating biotechnological methods to enhance drought tolerance and other stress resistance traits in sweet potato should be explored to ensure stable yields under changing climatic conditions.

Acknowledgments

The author sincerely thanks Professor Cai from Zhejiang Agronomist College for his in-depth review of the manuscript, constructive suggestions, and providing some relevant photos. The author also thanks the two anonymous peer reviewers for their valuable revision suggestions.

Conflict of Interest Disclosure

The author affirms that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

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