Overview
ISO 5525:1986 - "Potatoes - Storage in the open (in clamps)" provides international guidance for storing potatoes in open-air clamps (prisms/silos). The standard covers harvesting and handling before storage, clamp construction and orientation, covering and insulation, ventilation and cooling, humidity and temperature control, inspection and end-of-storage procedures, plus complementary preservation methods. An annex illustrates common clamp types. Guidance is intended for temperate climates.
Key topics and technical requirements
- Scope and applicability: Methods apply to potatoes intended for consumption and to regions with temperate climate.
- Harvest and handling:
- Tubers must be fully mature, free from disease-damaged tubers and largely free of adhering soil; wet tubers should be dried and marketed quickly.
- Gentle handling is stressed (dull forks, bucket elevators with rounded edges, slow tipping trailers) to avoid damage that promotes storage losses.
- Clamp geometry and siting:
- Recommended maximum prism width: 200 cm, height: 100 cm.
- Prisms oriented preferably north–south, located on level, well-drained sites; leave 5–6 m between longitudinal faces and 3 m between ends.
- Covering and insulation:
- Autumn cover: loose dry straw 60–100 cm (≈12–20 cm when tamped) with an optional thin earth layer 5–10 cm; leave a narrow rain-protected ridge.
- Winter cover: earth layer ≥25 cm (thickness may vary with soil type); additional earth or straw may be needed if external temperatures fall very low or snow cover is absent.
- Temperature and humidity control:
- Target inside-clamp temperature: +1 to +5 °C.
- Measure temperatures every 10 m along both sides of the clamp; thermometer should reach the top layer of potatoes and be left 15–20 minutes to record stable reading.
- Optimal relative humidity: 80–95% (control is difficult in open-air clamps).
- Ventilation and cooling:
- If internal temperature rises above +6 °C, remove (part of) the earth cover and ventilate; openings 60–70 cm wide can be alternately opened every 3–5 m.
- Avoid cooling below +2 °C during daytime; if it falls below +2 °C, cover ventilation openings with straw or similar.
- Inspection, sorting and storage life:
- Inspect clamps regularly; repair cracks and seal holes. If rot is significant or temperatures remain high, sort and remove decayed tubers; storage typically up to 8 months.
- Complementary methods: Use of ventilation devices and chemical sprout inhibitors may be applied in accordance with national regulations.
Applications and users
ISO 5525 is practical for:
- Farmers and growers using open-air clamp storage
- Agronomists and post-harvest advisors developing storage protocols
- Storage contractors, co‑operatives and extension services
- Supply chain and quality managers in potato processing and fresh markets
Related standards
- ISO 2165 - Potatoes - Guide for storage (referenced in ISO 5525 for in‑store techniques)
- National regulations on use of chemical sprout inhibitors and phytosanitary measures
Keywords: ISO 5525:1986, potato storage, clamp storage, open-air storage, prism storage, temperature control, ventilation, potato handling, storage humidity.