Creating the perfect ridge

Since our first part about Royal ZAP Spunta, it's time for an update of what has happened in Mr. Geluk’s field since. Far from resting on his laurels, Mr. Geluk has been busy finalizing the ridges. The ridges that were formed by earthing up his potatoes at planting time were small. Under the cool conditions of the moderate Dutch climate Mr. Geluk prefers planting his tubers shallow, as there is no risk of the potatoes becoming overheated or the surface soil drying out.

The advantage of covering tubers with only a moderate layer of soil at planting time is that the plants will emerge more rapidly. Since planting time, the tubers have had nearlytwo weeks to start their initial development. To transform the small, roughly shaped ridges into neat, well-developed ones, Mr. Geluk is using an inter-row cultivator. Under the hotter Libyan climate conditions however, potatoes will benefit from sturdy ridges formed at or immediately after planting, to protect them from the heat and drought.

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The bigger, the better

In general, the higher and wider the ridges, the better. As an experienced farmer, Mr. Geluk knows that if you give the potato more space in which to develop itself, it will use this extra space to grow not only more, but also bigger tubers, since all tubers form in the ridge above the mother potato.

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Benefits of good ridging

As said, well-developed ridges are multi-beneficial. Not only do they promote the development of bigger and more tubers per plant, they also protect against tuber greening. In hot and sunny climates such as that of Libya they protect against sunburn which causes brown spots on the potatoes that can lead to rot. Potatoes that have been exposed to the elements are also more prone to diseases and plagues, as they form an easy target for tuber moths, and infection by Late Blight (Phytophthora).

Apart from protecting against exposure, sturdy ridges also provide better protection from the heat. At the end of the Libyan spring towards summer when the Gibli, the hot winds from the Sahara, blow over Libya the soil can get very hot. This puts the potatoes at risk of the condition known as 'black heart', where the potato actually suffocates. At very high temperatures all tubers underground are at risk, but those nearer or at the surface will get hotter sooner.

As mentioned earlier, one of Spunta’s main strong points is it's high heat resistance. By creating good ridges, farmers can thus top off Spunta’s innate protection against hot conditions.


As Mr. Geluk took grate care to level his soil prior to planting, the tubers can be seen emerging quite simultaneously and evenly. Uniform emergence makes it more likely that the potatoes will mature around the same time, meaning that characteristics such as shape, size, and dry matter content will be more regular at harvest time as well. This in turn maximizes the yield of the field as a whole. Finally, regular emergence enables Mr. Geluk to administer fertilizer more efficiently, as the plants go through each growth phase simultaneously.

On uneven soil no mechanized ridging, planting, or sorting can take place, as damage to the potatoes is nearly inevitable. By spending so much time on the preparation of his seed bed and ridging Mr. Geluk largely determines the later success of his crop.