Growing sweet potatoes

Unless you obtain clean planting material from time to time, there is a risk of virus lowering yield and quality in your sweet potatoes.

Many old varieties have virtually disappeared due to gradual declining yield caused by viruses. Today, however, the technology exists to rejuvenate such varieties.

By buying cuttings from a registered grower, you are assured of getting clean planting material. This is especially important when starting out. Do not be tempted to get cheap cuttings from a commercial farmer; his crop may be infected and the symptoms may not be obvious.

If you are farming in a cold area, get an early start by purchasing cuttings from a registered grower in a warm area. These cuttings will be significantly longer than those grown in a cold area, you therefore won’t have to wait for your own plantings to become big enough.

Growing your own cuttings

To produce your own planting material, set aside an area on the farm, preferably isolated, for the purpose. This area should be carefully monitored for insect pests such as aphids and whiteflies. You can also consider using frost covering in late winter to stimulate growth for an earlier start.

As noted last week, the ARC has conducted research on the best material to be used for planting in Mbombela. It determined that tip cuttings are marginally better than those taken from further down the runner. Using other varieties, researchers in other countries have found an even greater difference. Whatever the case, cuttings should be about 30cm long and preferably taken from the tip.

Ensuring clean cuttings

If you produce your own planting material, make sure the cuttings are pest-free. Pests that are introduced at this stage may become a significant problem later on. When farming on the Mpumalanga Lowveld, we would always dip the cuttings in an insecticide solution. Several safe, effective solutions are available today.

Planting

There are a number of ways to plant this crop. The usual procedure is to draw ridges about 1m apart, but the exact distance can be adjusted slightly to accommodate the tractor’s wheels. The spacing in the row is about 30cm.

Fresh cuttings may be rather brittle, especially if they have been growing rapidly in a nursery. Allow them to wilt slightly so that they become more flexible for planting. Don’t wilt them to the point where the leaves dry up, though. The stems will still sustain the new growth, although it does slow down initial growth slightly.

The easiest way to plant is to have someone place the cuttings across the ridge, then a planter can follow and push them into the top of the ridge. For this, use a smooth, sturdy stick with a notch cut into the tip. Position the planting stick over the middle of the cutting and push down so that both ends of the cutting protrude from ground.The soil should be loose and moist, and planting must be followed by a light irrigation. The roots will start to grow within a few days of planting.

Position the planting stick over the middle of the cutting and push down so that both ends of the cutting protrude from ground.The soil should be loose and moist, and planting must be followed by a light irrigation. The roots will start to grow within a few days of planting.

High resistance

This is a tough crop that is resistant to several herbicides. This is not surprising, as sweet potato (Ipomoea batatas) is closely related to morning glory (Ipomoea convolvulus), one of the hardest weeds to control.

You can therefore use a number of herbicides, depending on the weed spectrum of the land. Regardless of what you use, you can apply Paraquat at 500ml/ ha with no adjuvants when the weeds are at the two-leaf stage; it will not harm the crop.