Barfoot Guide To Sweet Potatoes

Background:- The sweet potato (Ipomoea batatas) is a member of the Convolvulaceae family, is a perennial but is treated as an annual in cropping. Barfoots require orange fleshed varieties, with the recommended one being Beauregard.

The tuberous root is one of the, if not the most nutritious vegetable, being high in food value, fibre and energy. It is rich in sugar and Vitamin C, and also contains good quantities of vitamin A, Vitamin B, calcium and iron. They can be steamed, baked, boiled, microwaved, roasted or fried.

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 ideally 6 to 7 in saline free soils. Cultivate the soil to provide 20 to 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 humidities 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. Overwatering 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.