Unearthing Underground Crops

Back to the Roots

Unearthing Underground Crops - Back to the Roots
Unearthing Underground Crops - Back to the Roots
Yields for underground crops remain a mystery until harvest, along with the pests and diseases that could lurk just under the surface. The challenge of caring for these crops is tremendous – and much is at stake in cultivating these prized plants that mean nutrition and sustenance for millions.

Craig MacFarlane became a farmer unexpectedly. At age 20, he inherited Loch Buighe, the family farm in Ixopo, South Africa. Established in 1868, Loch Buighe sits on a misty landscape about 200 meters above sea level, an hour west of South Africa’s southeastern shore. Among the farm’s holdings is a 70-hectare stretch for potato crops.

Over the last three decades, MacFarlane has grown in confidence and farming knowledge. By 2015, he was named South Africa’s Seed Potato Grower of the Year. Walking between long green rows of burgeoning potato plants at Loch Buighe, he explains key signs to watch: “Yellowing leaves and lack of vegetative growth in the early growing stages,” MacFarlane says, “and wilting plants. These are important markers.” Recognizing these markers – and knowing what’s behind them – is crucial.

Loch Buighe is located in the south eastern part of South Africa.
Loch Buighe is located in the south eastern part of South Africa.
Loch Buighe is located in the south-eastern part of South Africa.

To be a successful potato farmer, like MacFarlane, is a tremendous challenge. Underground plants (roots, tubers, bulbs and stems) are actually plant organs, with a complex anatomy. These crops require special care: since their yields are underground, their condition may not be fully known until harvest. Worldwide, underground crops – including potatoes and ginger – are leading agricultural products. The potato, for example, is a major crop in about 130 countries. According to the FAO, root and tuber crops like potatoes are second only to cereals as the leading worldwide source of dietary carbohydrates. And ginger, once a regional product, is now grown, sold and desired globally. But despite how prevalent these crops are, growing them is tricky work, requiring the ability to observe tiny, almost imperceptible changes in anatomy and the ability to foretell what may be happening underground.

Keeping the Potatoes Coming

On his farm in Ixopo, South Africa, Craig MacFarlane values staple crops like potatoes: “Root vegetables produce nutritious food, packed with energy and minerals.” During South Africa’s double sowing seasons – a first season in May through June, and a second season in November – potato farmers begin planting. Four to eight weeks later, the crops are ready to harvest, even in South Africa’s semi-arid conditions. “Potatoes have a unique ability to grow in harsh conditions, and are hardy due to something special – a fibrous root system.”

Yellowing leaves and lack of vegetative growth in the early growing stages and wilting plants. These are important markers. Recognizing these markers – and knowing what’s behind them – is crucial.

Craig McFarlane, farmer in Ixopo, South Africa

South African potato production was more than two million tonnes in 2014. This is an increase of almost 400,000 tonnes since 2009.
Source: FAOSTAT, crop data

But this is where problems may start: While potato roots may be strong, they are typically not more than 60 centimeters long. MacFarlane explains: “Potatoes are shallow rooted compared to cereals, for example, which can root to at least 100 centimeters in depth.” As a result, potato roots are often unable to take up the nutrients and soil moisture at the depths where they are most available within soil. Potato crops also have specific soil preferences. “Potatoes will grow in just about any well-drained soil,” MacFarlane adds, “but they dislike soggy soil. Because they grow underground, they can expand more easily in loose, loamy soil than in heavy, compacted, clay soil that keeps plant roots from getting the air and water they need.”

Potatoes: Underground Plant Anatomy

Potato Plants
The visible part of potato plants – stems and leaves – can grow to more than one meter in height. The plant itself produces white or blue flowers and yellow-green berries – these are signs that, below the ground, the yellow, red or even purple tubers are forming. But they are not so far below: the tubers generally form in uppermost level of soil, roughly 25 centimeters (one foot) deep. Anywhere from two to four months after sowing, an edible tuber can be pulled out of the ground.

Water Management is Crucial

And there’s another challenge, warns South Africa’s Department of Agriculture: “Water management is among the most important factors determining yield and quality of potatoes.” Potato crops in South Africa require at least 460 mm of water – which is almost the average amount of rainfall in South Africa, but half the average of the rest of the world. An even slightly drier season, which happens more frequently with climate change, leaves soil, and potato roots, parched.

With a potential lack of nutrients due to naturally short roots and a lack of oxygen if the soil quality is poor and declining levels of water, potato crops can be vulnerable. Yellowing leaves, stunted development and wilted plants above the ground may be markers of starving roots, or even of potential disease and pests. While early and late blight – the later of which was the pathogen that led to the infamous 19th century Irish Potato Famine – are not a problem due to use of crop protection products, MacFarlane finds that his major challenges are soil-borne diseases and pests, including nematodes and aphids.

Dirk Uys, an agricultural manager at Bayer, agrees: “In South Africa, our challenges are aggravated by availability of water for irrigation.” Potato growers have difficulty finding suitable fields to grow potatoes, which puts tremendous pressure on rotation practices. “As a result, fungus-based tuber diseases, such as powdery scab and silver scurf, are increasing. Nematodes remain a major issue as well.” For many growers, crop protection products, when used as directed, are vital for prevention of these diseases. “Tuber health is an area of research focus,” says Uys. “We hope to introduce scientifically-based products, including biologics, in the near future.” At the same time, aphids are a problem since they can carry potato plant viruses. Uys describes an environmentally sustainable approach: “Farmers use an integrated program which includes both product rotation as well as physical inspection of the fields,” in order to identify and remove infested plants.

As a grower, MacFarlane understands the importance of starting with a quality product: “All aspects of growing potatoes have gotten so expensive that farmers can’t afford for anything to go wrong.” His strategies continue even after the crops have been harvested: “Green manuring of your lands will have a positive impact on your next rotation,” he adds. “Getting microbial activity in the soil helps in aerating the soil and improves drainage.” When growing root vegetables, MacFarlane notes, farmers have to focus on what’s happening beneath their feet. “Any extra nutrients we can work into the soil will assist in higher yields.”

Farmers use an integrated program which includes both product rotation as well as physical inspection of the fields in order to identify and remove infested plants.

Dirk Uys, agricultural manager at Bayer

Interview: Good Science – Good Potatoes

Joel Lipsitch is a Senior Horticulture Fungicide Product Manager at Bayer, based in Raleigh-Durham, North Carolina, USA. With a background in marketing and sales in crop protection, irrigation, and agricultural equipment, Lipsitch speaks to “Farming’s Future” about the special challenges of root crops and how science can assist.

What is special about the root anatomy of a potato?
Joel Lipsitch: It’s about growing the plant in order to enable that plant to put the sugar back into the tuber itself, and we consume that tuber. I think that’s quite different than if you’re growing lettuce. If you grow lettuce, you grow it to eat the leaves. So protecting the roots delivers different benefits.

Over the last decades, there is increased concern about changes in climate and demands on agricultural production levels. How would you say that the potato farmers are affected you work with?
Joel Lipsitch: Farmers have always taken a serious role in caring for the land they farm and that they plan to pass on to the next generation. That said, every day there is greater awareness of society’s desire to understand how food is grown and what measures were taken to sustain the environment. There is an understanding of better ways to manage water, better ways to steward the soil, so you have less runoff. There are much more sophisticated products that precisely target. These products have better overall safety profiles, including better environmental safety profiles. Over the last 100 years society has become more interested in stewardship. Since farmers also care deeply about this, it is great that they now have more and better tools to support their efforts.

More than ever, consumers are concerned about how their food is produced. Since you have an inside view of food production, including product usage, what would you say about their concerns?
Joel Lipsitch: First, I do all I can to understand these perspectives by listening. Every time we get a chance to have a conversation with someone, we learn something, and I enjoy that dialogue. I trust in science, and the more we talk about science, the more we can address the questions people may have. The real opportunity is to talk about that science in a way that makes sense to people, so we can create a common understanding of how we are helping farmers grow a safe and abundant food supply for a growing world.

Joel Lipsitch
Joel Lipsitch
Joel Lipsitch, Senior Horticulture Fungicide Product Manager at Bayer

Ginger – Waiting for Hidden Jewels

Nestled between Beijing, to the north, and Shanghai, to the south, Changyi County in China’s Shandong Province holds thousands of hectares of ginger farms. In fact, Shandong Province is one of China’s – and the world’s – largest producers of ginger.

Since antiquity, whether in China, Greece, Italy or India, ginger – a root plant – has been prized for both cooking as well as health benefits. While this sharp-yet-sweet spice adds flavor to beverages, desserts and meals, ginger can also treat a range of disorders, including arthritis, indigestion, and nausea. The plant itself is also attractive: The above-ground section of a ginger plant has delicate flowers; however, its subterranean stem – known as a rhizome – is the great prize for consumers. And in many countries, ginger is a highly valuable crop, providing an important means for farmers – particularly smallholders – to support their families.

Changyi County in China's Shadong Province is located between Beijing in the north and Shanghai in the south.
Changyi County in China's Shadong Province is located between Beijing in the north and Shanghai in the south.
Changyi County in China’s Shadong Province is located between Bejing in the north and Shanghai in the south.

Ginger Plant Anatomy

Ginger’s Family Tree
After ginger’s underground stem – the rhizome – begins to sprout, a ginger plant gradually develops a main stem. Then the main stem base gradually expands, forming a small rhizome called the ‘ginger mother’. The ginger mother will further sprout two to four buds and then develop a first ginger branch, called the ‘ginger son’. The process repeats, and the ginger son will grow a second branch to develop a ‘grandson,’ and then third, fourth, fifth, and so on until fully developed at harvest – which may take ten to twelve months, on average.

Sky Gao, a horticulture expert with Bayer in China, explains that ginger may seem easy to grow: “Ginger plants don’t require seed breeding, like potatoes, for example.” Instead, they develop via asexual reproduction. The ginger plant, says Gao, “has many visible qualities that reveal the health of the rhizome in the soil. Above the ground, healthy ginger plants will have a uniform shape and dark green, elastic leaves. The more branches above the ground, the more ginger tubers are likely to be growing beneath the surface. The thicker the stem, in general, the healthier the tuber.”

With so much visible evidence of ginger health, how challenging can it be to harvest this underground crop? Quite a challenge at times, as Changyi County farmer Yuhui Ma confirms. Nematodes and Pythium root rot (caused by a water-based, fungus-like organism) are ongoing problems. Yuhui Ma says that while nematodes can be controlled, ginger plants still sometimes show symptoms of attack. “And for Pythium root rot, once the plant is under attack, I don’t find a solution.” In some cases, root rot becomes worse with irrigation. “As a result, sometimes I have to find a new place to farm.”

Crop rotation reduces the rate of major ginger problems including Pythium root rot, ginger blast (a common bacterial disease) and nematode infestation.

Sky Gao, a horticulture expert with Bayer in China

Ginger Plants Under Tough Conditions

Like the potato tuber, the ginger rhizome is also a shallow root crop – which makes access to nutrients difficult. Ginger faces an additional, special challenge: It takes around seven months here to fully grow. Since ginger rhizomes need three to four times longer to cultivate than potato plants, the visible areas of ginger plant and the rhizomes below the surface face lengthy environmental exposure, including insects and disease. “In order to withstand them, quality soil, for optimal plant health, is particularly important for ginger,” says Gao.


From 2009 to 2014, the most recent year available, China increased its ginger production from 381,393 tonnes to 450,686 tonnes, an increase of just over 69,000 tonnes.
Source: FAOSTAT, crop data

In Shandong Province, Gao explains, ginger farmers improve soil quality with sustainable practices, particularly crop rotation: “Some farmers grow ginger for two years, then a non-root vegetable like corn for two to three years, then come back to ginger.” Crop rotation reduces the rate of major ginger problems including Pythium root rot, ginger blast (a common bacterial disease) and nematode infestation. Farmers like Yuhui Ma also emphasize soil preparation. This process includes the application of organic fertilizer, biological bacteria and humic acid – natural organic matter – for sustainable soil maintenance.

Challenges continue. In 2014 and 2015, drought and water shortages in Shandong restricted the scale of ginger planting. And while Pythium root rot cannot fully be controlled, farmers persevere. There is a good income to be made from ginger and growing it is gratifying. For Yuhui Ma and other farmers in the Shandong province, there is nothing more satisfying after a half a year of work than digging into the soil and finally holding their prized rhizomes in their hands.

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john peter
July 25, 2018 - 06:26 AM

Your good knowledge and kindness in playing with all the pieces were very useful.
I don’t know what I would have done if I had not encountered such a step like this.
virtual farming.

Current Readers´ rating (1)

Shiganga ligwa
May 13, 2017 - 11:56 AM

Thanks for your educative and encourageble facts ,, the big problem in Tanzania is how to protect the crops of the farmers especially on how to use buyer products,,, if possible seminar should be provided careful or product should be in kiswahili

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Bayer Crop Science
May 12, 2017 - 01:06 PM

Thank you for getting in touch with us. Could you please send us your e-mail address? Then we can get in contact with you and of course we won't publish your contact details here!

Best regards

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amaranath naidu
May 04, 2017 - 09:25 PM

Good basic information about potato and ginger. I would like to request to you i saw a video of green chilly crop growing in west sumatra and the height of plant is 2 to 3 meter high ,can i get the seeds of this variety ? can you help in this ?

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