This article was prepared and written by Jorge Luis Alonso G.
Researchers at the UK National Robotarium, School of Engineering and Physical Sciences, Heriot-Watt University in Edinburgh conducted a study to review global developments in potato harvesting, with a focus on mechatronics, the use of intelligent systems, and the opportunities presented by Internet of Things (IoT) applications. Fernando Auat Cheein and Ciaran Miceal Johnson report on their study in a scientific paper published in the journal Frontiers in Plant Science. The article below is a summary of the paper.
Introduction
Agriculture around the world is facing increasing challenges. These include a shrinking pool of skilled labor, the effects of climate change, and a growing population. Against this backdrop, the importance of potatoes cannot be overstated. As the world’s fourth most cultivated crop, they are essential to feeding a growing population. Significantly, the harvesting stage is particularly vulnerable, with potatoes often damaged or overlooked.
Interestingly, there’s no one-size-fits-all solution for potato harvesting. Factors such as farm size, regional conditions and soil type greatly influence the choice of harvesting method. In addition, the mechanical design will vary depending on environmental conditions. It’s worth noting that the harvesting method can dictate production results. For example, regions in the northern and central parts of the world have seen increased yields with mechanical harvesting.
When it comes to harvesting equipment, there’s a spectrum of complexity. At one end, there’s the rudimentary manual method using simple tools such as hoes or spading forks. Despite its labor-intensive nature, it is still widely used in some regions. At the same time, concerns have arisen about the welfare of animals used in traditional harvesting. The next step is mechanical harvesting. These advanced machines, especially the fully mechanized versions, offer distinct advantages such as reduced costs and minimized losses. An intriguing prospect on the horizon is the idea of automated harvesters, although it remains in the realm of theory for now.
This review aims to provide a comprehensive understanding of global potato crop trends. It highlights geographical differences and the reasons for them, examines the challenges associated with soil and potato types, and looks at current technologies and future developments. To ensure accuracy, the review is based on scientific journals from 2017 to 2022, as well as data from government sources, with a focus on machinery used in potato harvesting.
Potato harvest: An international assessment
Potato harvesting practices vary widely around the world, influenced by factors such as geographic location, which in turn affects terrain, climate and soil composition. As a result, each region requires its own tailored harvesting solutions. In regions such as Asia, Africa and South America, smallholder farmers largely view potatoes as a staple food rather than a lucrative cash crop. Recognizing this, there’s a burgeoning movement to encourage these farmers to adopt modern farming techniques designed specifically for their unique conditions.
In recent years, the dynamics of global potato production have shifted. In particular, Asia, led by countries such as China and India, has overtaken Europe in terms of production volume. Although Europe once held the mantle as the world’s leading producer, there has been a decline, particularly in countries such as Germany and the UK. China has prioritized semi-mechanized harvesting and is also venturing into post-harvest automation. Meanwhile, India is on a steady path to fully mechanized harvesting.
Before the significant political event of Brexit, five countries in Western Europe — Germany, Belgium, France, the Netherlands and the UK — were at the forefront of potato production. These countries rely heavily on mechanization and view potatoes from a dual perspective: as a staple food and as a cash crop. However, a decline in European production is noticeable, with Germany’s declining figures being a case in point. At the same time, the UK has reduced its potato production, albeit in a smaller area.
In Eastern Europe, Ukraine stands out as the third largest producer in the world. Their harvesting practices are predominantly mechanized, using equipment sourced mainly from Russia, Belarus and Germany. A significant hurdle they face is the removal of post-harvest clods, a byproduct of their dense clay soil composition.
In North America, potatoes are primarily a cash crop. Impressively, the U.S. has been able to maintain high yields even as its acreage has shrunk. In contrast, some South American countries, including Argentina, Brazil and Peru, tend to use semi-mechanized harvesting. Argentina, for example, often experiences losses due to prolonged exposure of harvested potatoes in the field.
Africa offers promising opportunities for increasing potato production, especially as its growing population requires higher yields without a corresponding increase in arable land. A case in point is Egypt, which has shown remarkable growth in production, population, and harvested areas from 2017 to 2021.
Finally, focusing on Oceania, Australia emerges as a key player in potato production. Although its contribution to global production is relatively modest, potatoes are of considerable economic importance to the country. Notable research in Australia revolves around the potential for highly automated harvesting. However, the transition to this advanced method is still in its infancy. In parallel with Egypt, both India and Peru join Australia in showing an upward trajectory in production, harvested area, and population over the 2017–2021 period.
Potato harvesting constraints
The efficiency of potato harvesting is influenced by several factors, which can mainly be categorized into potato characteristics and soil characteristics.
Potato characteristics that affect harvesting:
- Understanding potato characteristics can lead to better harvester designs, optimizing yield and minimizing waste.
- The physical properties of potatoes, such as diameter, mass, and volume, affect sorting, packaging, and segregation during harvest.
- Mechanical properties such as modulus of elasticity and fracture strength, derived from uniaxial compression tests, help to design machines that reduce waste.
- Many of these properties are correlated with potato size. The relative density (specific gravity) of potatoes indicates their dry matter content and gives an indication of water content. Higher specific gravity is desirable because it allows for efficient harvesting and less damage to the potatoes.
- Specific gravity can be affected by factors such as harvest time and potato variety. Certain varieties, such as Clearwater Russet, have a higher specific gravity.
- Potatoes can be selectively bred for desired characteristics. Higher specific gravity not only benefits the harvesting process but is also financially beneficial to growers through incentive pricing.
Soil characteristics that affect harvesting:
- Appropriate agronomic practices tailored to a potato variety can improve the quality of potatoes produced. Nutrient requirements vary throughout the growing cycle, which can be addressed through practices such as intercropping.
- Intercropping aims for a Land Equivalent Ratio (LER) greater than 1, indicating cooperative resource sharing between crops. This method can reduce weeds and disease. Potato harvesters should be designed with the presence of other crops in mind.
- Crop rotation is another method that offers benefits similar to intercropping and reduces the challenges of managing multiple crops.
- Soil type and moisture content have a significant impact on potato damage during harvest. For example, heavy clay soils can lead to compaction, causing bruising and damage to the potatoes. Controlling soil moisture through irrigation can promote optimal potato growth, but it’s important to balance yield optimization with environmental impact.
In summary, both potato-specific traits and soil conditions play a key role in determining harvest efficiency. Adjusting practices and optimizing equipment designs to account for these factors can lead to improved yields and reduced waste.
Mechanical harvesters
When harvesting potatoes mechanically, several adjustable parameters can influence the efficiency of the machine. These parameters, in turn, are affected by both soil and potato characteristics. For example, the primary parameters to consider are the harvester’s forward and conveyor speeds, digging depth and angle. The forward speed determines the speed at which the harvester travels across the field, while the conveyor speed determines the speed at which the potatoes are removed from the ground.
To optimize these parameters, one must first understand the grower’s primary objectives. These objectives are primarily focused on minimizing potato damage and loss while maximizing harvest efficiency. It’s important to note that changing one parameter, such as forward speed, can have multiple results. For example, a faster forward speed may reduce tuber damage, but may also result in more tubers being left behind. Conflicting results from different studies further complicate these considerations.
Similarly, changes in digging angle and depth can affect tuber loss. Increasing the digging angle, while potentially reducing potato damage, may reduce efficiency due to increased soil resistance. Conveyor speed is another critical factor. Increasing this speed can increase the efficiency of separating potatoes from the soil, but there’s a potential downside: it could also increase the risk of potato damage, especially if potatoes are dropped at a higher speed. Unfortunately, there’s no clear research consensus on the optimal settings, with different studies reporting different results on the impact of conveyor speed on parameters such as tuber damage and lift percentage.
The world of harvester design offers a wide range of research. Designs range from those that emphasize basic specifications such as depth and speed to more sophisticated designs that incorporate features such as agitators and rotary components that help separate potatoes from clods of soil. A major challenge for designers is striking a balance: how to achieve maximum efficiency without causing undue damage to the potatoes.
There are several innovative strategies for improving harvesting efficiency. Some suggest using digging components equipped with cutting discs and soil compactors. Others advocate designs that can handle multiple rows of potatoes simultaneously, optimizing labor and machine use. A notable component in some designs is the spiral separator, which is designed to improve soil separation from the potatoes.
Therefore, the search for the perfect mechanical potato harvester is a complex one that requires careful consideration of many factors. The delicate balance between efficiency and minimizing damage is paramount. Ultimately, harvester design decisions should be based on rigorous research and tailored to the unique needs of each farming scenario.
Trends in potato harvesting
Electronic potatoes and their role in force analysis:
Remarkably, electronic potatoes have been developed to mimic real potatoes. Equipped with sensors, they document the forces to which they are subjected during the harvesting phase. These innovative tools play a critical role in deciphering the forces at play throughout the harvest, providing a basis for designing and selecting appropriate harvester specifications. However, their accuracy in reflecting real potatoes remains a challenge. While concerted efforts have been made to perfect their impact characteristics, a significant number of these simulated potatoes fail to capture the true essence of their real counterparts.
Highlighting the need for accurate harvest waste reporting:
There is an increasing emphasis on refining protocols for reporting potato harvest waste. Unfortunately, current practices sometimes omit certain categories of waste, such as post-harvest disposal of undersized potatoes. Comparative studies, such as those between Austrian and German farms, focus on two primary loss classifications: potatoes left on the ground and potatoes eliminated due to quality or technical discrepancies. Such research underscores that these losses vary based on multiple determinants such as regional variations, climatic conditions, the type of crop, and the harvesting technique chosen. In particular, variables such as digging intensity and speed of operation have a significant impact on the extent of potato loss.
A paradigm shift to renewable energy in potato farming:
In line with the global shift to renewable energy and electric transportation, the potato harvesting sector is also undergoing transformative changes. Analyses, such as those from Scotland, are highlighting the economic viability of solar and wind energy, trumping conventional sources such as coal and gas. These studies underscore the paramount importance of a steady flow of energy for agricultural endeavors, suggesting that a combination of wind and solar power can meet year-round energy needs for harvesting. With the growing push for sustainable agricultural practices, there’s a plausible increase in demand for electronic farming equipment in the foreseeable future.
The conundrum of autonomous vehicles and soil density:
The advent of low-mass autonomous vehicles has sparked curiosity about their impact on soil bulk density, with a particular focus on the implications for potato production. On the surface, the integration of mid-sized autonomous machines with Controlled Traffic Farming (CTF) appears promising. However, CTF is insufficient for root and tuber crops because it requires machines to drive directly over vegetation. Alarmingly, even lightweight autonomous vehicles have been observed to exacerbate soil compaction, underscoring the need for inventive adaptations to harvesting equipment design.
Discussion
Understanding potato characteristics plays a key role in refining the design of both harvesting and post-harvest equipment. To build a solid foundation, it’s important to not only build on previous research to avoid duplication, but also to provide critical details. In particular, information on soil types and growing conditions is critical to improve the reproducibility of experiments.
Shifting the focus to the relationship between arable land and population, a general trend emerges: the larger the area harvested, the greater the potato production. Larger populations in countries naturally equate to more significant potato production. However, there’s an inverse dynamic at play: as the area under cultivation expands, the yield of potatoes tends to decline. The exact relationship between a country’s population and its potato yield remains somewhat unclear.
When discussing harvester specifications, they are largely determined by field conditions and the specific design of the potato harvester. Differences in research results are mostly due to differences in soil types and harvester design. For example, potatoes from dense clay soils suffer different tuber damage than those from sandy loam soils. The intricacies of the machine’s design also dictate the force exerted on both the soil and the potatoes, which in turn alters the harvest results.
There is a wide range of levels of automation in potato harvesting around the world. This spectrum ranges from the rudimentary Level 0, which indicates manual labor, to the sophisticated Level 5, which represents full farm automation. In particular, Level 2, with a fully mechanized harvester, stands out as the pinnacle in current automation reports. Different countries take different approaches. A handful go the fully mechanized route, while others, such as Egypt, lean toward semi-mechanized harvesters.
A country’s choice of automation is influenced by its research history and dominant farming methods. Trends also point to evolving practices. For example, although countries like China and India have been known for their semi-mechanized systems, recent studies indicate a pivot to a more mechanized approach. Similarly, in regions such as Ukraine, the prevalent manual methods may soon give way to a more mechanized system, according to recent findings.
Conclusion and future work
Potato harvesting is a complex process that requires customized solutions. This is because conditions and the unique characteristics of both potatoes and soils vary around the world. Much has been said recently about the potential for automation in this area. However, the prevailing method still relies heavily on fully mechanized harvesting. One of the main focuses of current harvester designs is the elimination of soil clods. With the rise in environmental awareness, it’s possible that future harvesters will move to electric operation.
Intelligent systems, such as those that mimic the characteristics of potatoes, have the potential to reduce damage to tubers. They do this by assessing the forces applied during the harvesting process. Despite their promise, there seems to be a noticeable gap in research exploring these innovative systems. Filling this research gap could be critical, especially given the dual challenges of a declining agricultural workforce and a growing global population.
Source: Johnson, C. M., & Auat Cheein, F. (2023). Machinery for potato harvesting: A state-of-the-art review. Frontiers in Plant Science, 14, 1156734. https://doi.org/10.3389/fpls.2023.1156734
Cover image: Credit Jorge Luis Alonso G
