Advice For New Potato Producers
Potatoes can be produced with success in most areas of South Africa. In fact, in some regions you can produce two crops a year.
Climate
This is a cool weather crop that realizes its highest yields and best quality in regions that have a temperate climate and a long average day length during the growing season. Diseases, pests and water stress at any time while the potatoes are growing are major constraints to production. Consult your local co-operative for assistance and guidelines on cultivars. Potatoes are easily killed by frost, so do not plant a cultivar that has a long growing period if there are only three months from the date of planting to the first frost.
Guidelines Winter Vegetables
Soil preparation is to break up compacted soil, incorporate crop residues, control weeds and seedbed preparation. Pre-planting tillage: The soil should be slightly moist when tillage takes place to prevent deterioration of the soil structure. Cross-rip the field to a depth of at least 50cm. Deep ripping is important as the plant has a relatively weak root system and is sensitive to compacted soil layers.
After ripping, the field must be ploughed to a depth of at least 30cm. This should incorporate all crop residues to ensure complete decomposition of any plant material before the potatoes are planted. A disc may be used to break any clods and level the field. Seedbed preparation directly before planting: Irrigate lightly before preparing the final seedbed to ensure the soil is moist at planting and that any remaining clods break up during tilling.
A well-prepared seedbed consists of a 15cm deep layer of loose and finely crumbled moist soil. This can be obtained by tilling with either a spring-tined cultivator with a roller, a rotavator or a disc.
Cultivar choice
For Short grow Vanderplank is advised. Short-medium grower: Buffelspoort. Medium grower: BP1. Long grower: Mandi (Natal, Eastern Cape). Pre-plant soil testing is necessary to determine the chemical status. Potatoes are adapted to a wide soil pH range, but it may be necessary to modify the pH to optimize production. This can affect nutrient availability and the activity of soil pathogens. Potatoes require a high level of soil fertility, so soil that has low inherent fertility must be given high inputs of nutrients from organic or inorganic sources.
Planting
Plant the seed slightly to the side of the furrow or cover the fertilizer with a thin soil layer. Where top dressing is recommended, apply it on both sides of the plant just before ridging, then ridge and irrigate. A central pivot irrigation system in a potato field. Planting Potatoes should be planted when the soil is still moist (irrigate before planting), but not wet. Plant the tubers about 20cm deep in a furrow to which fertilizer has been applied.
Close the furrow with the soil removed during the opening of the furrow and irrigate the dry soil lightly. The spacing between rows for potatoes grown under irrigation may vary between 75cm and 100cm, depending on the size of the tractor and the setting of the implements used. Without irrigation (rainfed) the spacing between rows is usually at least 1,25m.
The space between seed tubers in the furrow (row), depends on the size of the tubers. Small seed or “chats” are usually spaced 15cm apart, while medium-sized seed (80 — 100g) may be spaced 30cm apart. Potato plants are ridged after they are well established (plants 20 — 25cm high), to ensure the developing tubers will be covered with enough soil to avoid sun damage. Also, it protects them from attacks by pests and diseases. Ridging when the soil temperature is high can damage the plant stems and cause lower yields. Avoid this by irrigating lightly before ridging or immediately afterwards.
Potato Harvesting
Potatoes can be harvested as soon as the tubers have matured sufficiently to resist mechanical damage. In most cases, the skin of the tubers will be properly set (or matured) about two weeks after the plants have died. Readiness to harvest may be checked by digging up several plants from different areas of the field and rubbing the tubers with your fingers. If the skin rubs off, the tubers should be left in the soil for another 7 — 10 days to ensure that the skins have matured properly. The soil must be slightly moist when the potatoes are harvested. JS (with assistance from ARC-VOP)