CULTIVATION AND TECHNOLOGY Proper ridging important weapon against green discolouration Do not forget the soil loosening factor If you want to avoid green discolouration, the most important thing is to prepare the ridges with care. What follows are, in general, the well-known measures during planting and ridging. The seed potatoes must be planted sufficiently deeply, depending on variety and purpose. Coarse-growing chip potatoes can be planted as far as 2 centimetres below ground level. When checking the planting depth, a grower needs to consider the soil loosening factor because loosened soil subsides by 2 centimetres after preparing ridges. This means that, in recently cultivated and therefore loosened soil, a seed potato can be planted to a depth of up to 4 centimetres. If not planted deeply enough, the tubers grow too high in the ridge and if the potatoes are big they will suffer from green discolouration. Keep planting distance exactly the same There are a few more measures that you can take to prevent green discolouration of potatoes. It is, for example, important to keep the planting distance always the same. When potatoes are planted too closely, the tubers won’t have space to grow and will want to grow upwards. In such cases, you will find cracks high in the ridge and tubers can be affected by green discolouration. Furthermore, it is important that each potato ends up right in the middle of the planting furrow. A good quality potato planter has technical provisions fitted. Don’t make the soil too fine when ridging Only at the very last moment does the quality of the ridges become important. Very imporCultivator causes limited puddling. tant when using the inter-row rotary cultivator are the construction, form and material of the ridger. For light and for dry, heavy soils, you need a long ridger which holds the soil for a length of time. It is handy to have a hydraulic ridge pressure regulator. From the moving tractor, it is then possible to adjust the soil pressure if the composition of the soil varies a great deal. In light and intermediate soils it is important to make the soil not too fine and the sides should not be pressed too much. That also encourages cracking. Soil that is a little bit loose with clods on the sides is not too serious, because loose soil does not crack. When cultivating light and muddy soils, Den Boer advises to use subsoilers, so that in steady rain the water between the ridges can run off. Furthermore, it is also important that the potato is planted in the middle of the ridge, also to prevent green discolouration. If you plant in a straight line, it is not difficult to use the cultivator. More important, however, is that the inter-row rotary cultivator takes exactly the same route as the planting machines. If you use an all-inone combination, that is not a problem. But there are now plenty of aids on the market for separate ridge building that helps you plant the potatoes exactly in the middle of the ridge. Automatic steering equipment and RTK GPS steering are some examples. ● Keep the planting distance the same. Leo Hanse Ridge width Ground level Bottom of the ridge Cultivation depth Sub- soil platform Exterior ridge height Interior ridge height Subsided topsoil Pootdiepte: rasafhankelijk, constant! Moderately fine crumbled soil without clods > 40 mm Potato in the middle of the ridge Smooth , somewhat pressed sides Ridge width : 18 – 23 cm Interior height : >18 cm, constant! Plant sufficiently deeply. Don’t press the sides too much. Potato World 2010 • number 1 25 Pagina 24
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