The seed potato planting process

It is important to apply fertiliser within reach of each plant’s root system when planting seed potatoes, says Bill Kerr.

Potatoes have a compact root system and, because they produce a high yield, they need to be fertilised accordingly. Rows are spaced 70cm to 90cm apart, so it’s preferable to apply all the fertiliser within the reach of the root system at planting.

Most farmers use an implement which opens up a furrow, drops a seed potato into the furrow and then covers it, all in one operation. The spacing set is determined by the size of the seed potatoes; the smaller they are, the closer the spacing in the row. (A small spacing is 20cm, and a large spacing is 30cm to 35cm.)

Some farmers use double rows, which has the advantage of keeping the soil moist for longer. With single ridges, more soil is exposed to drying out. The downside of this approach is that a more powerful tractor is required for all tasks. It is common practice to plant the tubers when the eyes start to produce shoots. If they become too advanced, they may become damaged during planting. Ideally, the shoots should be 2mm long.

One advantage of planting in soil moist enough to start developing roots is that weeds are unable to develop, whereas the tubers are. This gives you a head start against weed development.

DRY SOIL

Sometimes, the potatoes may be ready to plant, but there is a risk of frost damage when they emerge. In this case, plant the tubers in dry soil and irrigate them later when it’s safe to get them going. Make sure, however, that the entire land is uniformly dry or the shoots may emerge too early in patches and be damaged by frost.

If the seed potatoes are far from being ready when the planting season approaches, you can buy products that speed up the stimulation of shoots.

Potatoes too fresh from harvest are in a dormant state for several months. Planting these speeds up the sprouting process, but often results in uneven emergence, which affects all the subsequent field operations. Rather avoid taking the chance.

If the site is warm, you can also spread out the potatoes and cover with moist compost to get them to sprout earlier.

Potatoes are highly favoured by cutworms, so ensure that you control this pest in good time. A pyrethroid spray well before emergence will take care of the threat.

PLANT DEEPER

The depth of planting also has a bearing on the time to emergence. If your seed potatoes have to be planted due to their stage of development, but there is a threat of frost, plant deeper to delay emergence. Some varieties also prefer to be planted deeper.

If you plant deeper in moist soil, you can delay the first irrigation even longer.

The roots grow below the mother tuber and the potatoes develop above it. So with any subsequent ridging, make sure enough soil is moved up against the stems to prevent the tubers from pushing through the soil and greening.

All mechanical operations should be carried out when the soil has the right moisture content. This simplifies operations and prevents deterioration of the soil’s condition.

Bill Kerr is a vegetable specialist and a breeder of a range of vegetables. Email him at farmersweekly@caxton.co.za. Subject line: Vegetable production.

SOMETIMES, THE POTATOES MAY BE READY TO PLANT, BUT THERE IS A RISK OF FROST

BILL KERR A newly ridged potato land. The ridged soil covers weeds and developing tubers.