Sweet Potatoes

9 400 tonnes of sweet potatoes per year, all proudly grown in South Africa, with great tastes and different colours supplied to retail markets.

South Africa’s climate is perfect for the cultivation of sweet potatoes, but producing great produce is not all you need. A strong market and a reliable avenue to the retailers is what keeps you ahead of the game.

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Nutritional Benefits

Sweet potatoes are a rich source of fibre as well as containing an array of vitamins and minerals including iron, calcium, selenium, and they’re a good source of most of our B vitamins and vitamin C.

General Growing Conditions

The plant

Sweet potato (lpomoea batatas) is not related to the common potato. Sweet potato belongs to the morning glory family and produces edible storage roots. The crop plays an important role in food systems of Southern Africa countries, including South Africa. Sweet potato is an important food and poverty relief crop that can be used to combat widespread Vitamin A deficiency which compromises the immune system and eye health.

Soil type and pH

Sweet potatoes grow well in sandy-loam, loam or clayey-loam soil. The crop needs good drainage and is sensitive to waterlogging, salinity and alkalinity. Optimum pH (H20) is 5.6 – 6.5. Stony or clay soil is not good, as it does not allow the formation (development) of good storage roots.

Growth period

The storage roots are usually ready for harvesting 4 months (warm areas) to 5 months (moderate areas) after planting. Soil should be soft during harvest to prevent breakage and skin damage. Withhold watering from around 30 days prior to harvesting as a way of field curing. In warm areas cut vines 4-7 days before harvesting to cure.

Irrigation

Sweet potato is moderately drought tolerant. It means that the plant will still produce a yield under fairly dry conditions. But lack of water will reduce the yield. Water stress during the first few weeks after planting and the period of storage root formation (30-60 days after planting) will cause low yields. As a general guide, sweet potato requires between 450 and 600 mm of water well distributed throughout the growing season.

Special Sensitivities

Sweet potato weevil

Adult weevils feed on foliage. The larvae tunnel into the storage roots and stems.

Hawk moth larvae

Large green to brown larvae (caterpillars) with a tiny “horn” on the dorsal back of the body. They feed on leaves during the evenings.

Fusarium wilt

aused by Fusarium oxysporum, this disease can cause severe yield loss. When cutting through the stem of an infected plant, a reddish-brown discoloration of vascular tissues can be seen. The leaves turn yellow, blacken and die. Infected plants also infect the soil.

Storage Diseases

During storage, soft rot, surface rot and dry rot may occur.

Planting and Fertilizing

Fertilisation Timing

Soil samples should be taken few months before planting in order to rectify soil fertility problems. Different fertilizer products can be applied depending on the soil type. Ammonium sulphate will tend to reduce soil pH while LAN will increase soil pH.

Sowing and Planting Time

Areas with light mild frost: Beginning of November to mid December. Areas with heavy frost: Mid November to beginning of December. Frost-free areas: August to March. In cooler areas September to February. Winter rainfall areas: mid November to beginning of December; November is optimal.

Planting Method

Propagation is by stem cuttings. Pieces of stem of 20-30 cm long should be taken for cuttings. The leaves may be removed from stem cuttings before planting, but it is not necessary. Top cuttings are more vigorous than cuttings from the other parts of the vine. Sometimes cuttings are prepared from storage roots: Plant the storage roots just covered with soil. When sprouts are 25-30 cm long, break them off and use for planting.

Fresh from the Kitchen

using Sweet Potatoes

Sweet Potato Salad

We love this salad warm, straight from the oven. But it’s also very good at room temperature one (two or three) days later. Bulk it up with leafy greens or put it in a wrap if you want!

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