Agroscope, Institute for Plant Production Sciences IPS, 1260 Nyon, Switzerland

Experiences with the soil separation technique in potato cropping

“The question whether a new cultivation method is compatible with the soil fertility is twofold: Firstly, is there a way to handle the technique in order not to endanger the soil fertility? And if yes, secondly, is the application done in that way?<br>Soil separators were introduced in the German speaking part of Switzerland in 1995. Separators sift stones and clods out of the potato ridges and put them into laterally dug furrows. The potatoes are then planted into the screened soil””. This technique allows an efficient harvesting as next to the potatoes there are no hard parts with a similar size left. Related to this technique the questions posed above are of extraordinary importance. The separation technique enables the user not only to change durably the structure but also the composition of the soil, e.g. by shifting the stones out of the A horizon into the subsoil.<br>An inquiry of 25 farmers that recently used separators on part of their potato cropping showed that – using the technique for the first time – recommendations concerning soil protection were scarcely followed. 60 % dug the furrows into the sensitive subsoil, only 12 % regarded accompanying soil observations as necessary. 20 % of the separated soils were heavy and therefore hardly suited for potatoes. Nevertheless, 86 % of the farmers made positive experiences deciding to use the technique further on.<br>An additional telephonic inquiry in May 1998 with six private contractors in German speaking Switzerland drew a different picture: After four years of application, optimization processes of the technique to the given location lead to modifications in the use. Separation is concentrated on light soils with lots of stones, and soil moisture is increasingly taken into account. These processes are driven by economical considerations. if they result in positive tendencies for the soil, it is by mere chance! A concluding judgement of the technique cannot be drawn yet: Criterias to evaluate the compatibility of different separator machines with soil fertility are still lacking.”

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