Cultivation on top of the soil reduces leaching

No longer growing crops in the soil but on top of it. This is the essence of revolutionary new cropping systems for a number of vegetable crops. Researchers at Applied Plant Research (PPO) are developing such systems, together with the Zwaagdijk experimental garden, growers and advisors.

Outdoor cultivation of crops on top of the soil seems to be a solution for a number of vegetable crops. Of the crops investigated until now, such as leek, cabbage, leafy crops and strawberry, yield and quality increase whereas nutrient losses show a considerable decrease. This means that the researchers have found a way to tackle a problem that has existed for a longer period of time. Field vegetable cultivation often, certainly on sandy soils, involves too large losses of nutrients to surface water. And this means that the criteria laid down in European legislation are occasionally strongly exceeded. Earlier research showed that it is not possible to adapt the conventional cultivation systems in such a way that the criteria could always be met. This means that the government may in the future impose restrictions on crop cultivation.

Meeting market demands

Cultivation on top of the soil does not only reduce nutrient leaching. It also helps growers to meet the strict requirements of their clients: uniform and high quality products throughout the season. These requirements are difficult to meet with current cultivation systems.

And cultivation on top of the soil also prevents soil-borne diseases and improves labour conditions.

Cultivation on top of the soil

In the new systems the crops are growing on top of the soil in a recirculating system. The precise set-up depends on the crop. Leek is, e.g., grown in a small tube on large plates in a floating system while strawberries can best be grown in gutters.

It has meanwhile been shown that it is quite well possible to grow crops loose from the soil. The next step is to make the system ready for application in practice. In doing so the researchers are taking three aspects into account:
1.    Cultivation technique. Questions to be answered: how long can the water in the system be used before quality loss is too high? And when the grower has to discharge water, how can this best be done without polluting the environment.
2.    Cost-effectiveness of the system. Important questions are: how high can yields be and how much labour can be saved with these systems?
3.    Application by farmers and growers. Questions to be considered: what about the marketing of the products, are the systems in line with legislation and regulations, and how does the general public rate the new systems?

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Experimental Garden Zwaagdijk (Dutch)

Website Cultivation on top of soil (Dutch)