The Barfoot Guide to Sweet Potatoes
Background
The sweet potato (Ipomea batatas) is a member of the Convolvulaceae family and is not actually a true potato at all - being closer to the tuberous root Yam and does not have the starch content of white potatoes. Sweet potato is comparatively a nutritional heavy weight: rich in complex carbohydrates, Vitamin C, Vitamin E and also containing good quantities of vitamin A, Vitamin B, calcium and iron. They can be steamed, baked, boiled, microwaved, roasted or fried. Perfect for the kitchen adventurer!
Due to climatic inappropriateness, sweet potato cannot be grown commercially in the UK and largely comes from sub tropical regions along the 34 parallel (where the sun shines for most of the year).
Of all the varieties available, Barfoots of Botley have sourced and marketed the orange fleshed varieties Beauregard and Jewel to the UK since 1999 on the basis of their exceptional sweetness and health properties. Sales growth for this exotic newcomer to the supermarkets has been outstanding and in 2004 Barfoots have extended the range of available varieties to include the New Zealand Kumara.
Orange Fleshed Varieties: Beauregarde & Jewel
History: - American Indians were growing sweet potatoes in the present day southern states of the USA when Columbus discovered America in 1492. Research by the Louisiana State University (LSU) Agricultural Department suggests that sweet potatoes are one of the oldest foodstuffs in the world existing since prehistoric times; with some scientists speculating that dinosaurs might even have eaten them. It therefore made sense to Barfoots to research supply of sweet potato from the World's most established source, the USA , where sweet potato is part of the staple diet.
Innovation in varieties: Jewel V's Beauregarde: Barfoots source Beauregarde variety sweet potatoes from American Farms January through to August; switching to Jewel variety from Israeli sources August through to January to complete the year round supply chain.
This decision is based in the historical battle between the leading two varieties. Until 1970, Louisiana led the USA in sweet potato production before a pivotal event occurred: North Carolina developed a new variety called Jewel, which was high-yielding, attractive-looking, great-tasting and well-adapted for the sandy soils of that state. Jewel soon took over as the most popular sweet potato variety in the USA and North Carolina became the market leader for sweet potatoes. At that time, sweet potato cropping in Louisiana dropped from more than 100,000 acres in the 1940's to fewer than 20,000 acres by 1980 and was nearly bankrupted. However, in 1987 Dr. Larry Ralston, an entomologist with the LSU Agricultural Centre's research team, founded a new variety. In his effort to find a more pest and rot resistant sweet potato, Ralston created the Beauregard - named after General Pierre Beauregard who fired the first shot of the American Civil War in 1861.
In its 17th year of production, Beauregard has helped Louisiana reclaim its lost market share and with it's disease resistant properties, richer texture and nuttier flavour the Beauregard has performed well in the export market and is now the leading variety sold by Barfoots into UK supermarkets. Although possessing a better skin finish, the Jewel variety has a shorter shelf life. For this treason it is solely imported from Israel, where it has adapted well to growing conditions and can be exported quickly to the UK, reducing quality issues such as rots.
Kumara
History: - The kumara has a long history of cultivation in New Zealand . Brought by the early Maori settlers in about the 10th century from its Pacific Island source (Hawaiki) , it was widely grown especially in the semi-tropical regions of the North Island . Archaeological diggings at the Waipoua Forest near Kaipara have revealed kumara cultivation from very early Pre-European Maori times.
The Maori managed kumara growing with great horticultural skill, making use of the ideal growing climate and controlling kumara caterpillar with the use of tamed black-backed seagulls. Kumara caterpillar could devastate a crop almost overnight, hatching in their thousands. Pre-European Maori grew several different varieties of 'bush' kumara, but compared to modern hybrids, were very small in size, being similar to the modern Anya potato variety.
Modern day kumara has evolved from cross breeding with a larger American hybrid imported in the 1850's. A dark red variety was developed which grows on a creeping vine and was named Owairaka Red. The majority of kumara are grown in Northland in the Northern Wairoa region where soil type and climatic conditions suit kumara perfectly. Kumara is the 3rd most popular vegetable in New Zealand and is revered by Maori as a cultural culinary emblem. Barfoots of Botley are the first company in the UK to import Kumara from New Zealand and market it to the British consumer.
Agronomics Of Sweet Potato
Climate:-The sweet potato is a semi tropical plant that grows best between 20 and 30C requiring a minimum of 5 months of frost free growing conditions. Plant growth is restricted below 10C and plants physically damaged at 1C. Optimum growth occurs between 20C and 30C, and optimum "tuber" growth (they are not really tubers) occurs during shortening days.
Soils:-Sweet potatoes grow best on well drained sandy loams. Heavy soils should be avoided. The pH of the soil is ideally 6 to 7 in saline free soils. Cultivate the soil to provide 20-30 cm of well worked soil. Additional sub soiling will be needed if soil compaction is present to improve drainage and root shape. Ridged beds will aid harvesting.
Planting Material:-Sweet potatoes are propagated vegetatively from cuttings called slips. These slips should be well watered before planting and kept at high humidity's to encourage rooting. However long roots are not encouraged and avoid immersing otherwise the tip will rot. About 1000 tip cuttings will come from 20kg of roots in total.
Cuttings are planted by hand, with 5 to 7cm of tip exposed. It is best to plant the cuttings half horizontally to the ground rather than vertical. Row sizes vary depending on climate and potential yield, but in good cropping areas rows should be 100cm apart and plants 30 cm apart. However if mechanical harvesting is planned bed spaces will vary- ridges 1.2m apart can be formed, with double rows 30 cm apart and 50cm apart within the row.
Irrigation:-Sweet potatoes do not like too wet conditions, however at planting it is important the soil is kept moist to ensure good establishment. Yields and quality are seriously affected if the crop is stressed when the harvest roots develop. Over watering though will cause rotting and skin cracking.
Fertiliser:-Sweet potatoes require less fertiliser than other vegetables. Individual recommendations will vary depending on previous cropping and soil analysis before planting.
Weed Control:- Sweet potatoes are ideal suited for mechanical weeding. During early crop growth, shallow cultivation between rows and hand weeding will control weeds. Once plants cover the ground, the crop tends to smother further weed growth.
Pests and Diseases: - The sweet potato crop is relatively free of pest and disease problems. Following a good rotation and hand weeding will minimise the need for pesticides. However Fusarium is the main cause of root rot, which increases in cold wet soils. It can progress rapidly within the root, so early harvest in warm condition should be encouraged.
Harvesting: -See Specification for optimum harvest size. Remove vines before digging the potatoes. The sweet potato is very sensitive to bruising. As such all harvesting and handling must take place with extreme care.
Storing Roots:-Do not wash roots intended for storage. Sweet potatoes must be cured by holding them at high temperatures (plus 25C) with a high relative humidity (90%) for upto 2 weeks. This cures the roots by healing the wounds, keeps shrinkage and weight loss at a minimum and improves the culinary qualities of the tuber by converting starches to sugars. |
