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Low-tunnel non-woven covers for vegetables

Low-tunnel non-woven covers are short hoop-supported tunnels of UV-treated polypropylene fabric stretched over vegetable beds to create a low-cost protective microclimate. They occupy the middle ground between open-field cultivation and full polyhouse protected cultivation, costing a fraction of either shade-net or polyhouse construction.

Principle

The non-woven polypropylene fabric is air-permeable, so no manual ventilation is required even on warm days. The cover moderates temperature within the canopy, raising ground temperature by 2-3 degrees C, blocks heavy raindrop impact, deflects flying pests, and provides partial frost and sunburn protection. Because the fabric breathes, condensation does not accumulate as it does under impermeable polyethylene tunnels.

Implementation

Standard fabric specification is 17-23 GSM UV-stabilised non-woven polypropylene, stretched over 1-2 m galvanised iron hoops on 1-1.5 m spacing. Edges are anchored with soil or sandbags. The cover is typically installed at sowing or transplanting and removed for harvest; in some crops the fabric remains in place through harvest. Sheets are reusable for 2-3 successive crops and the total system cost runs 10-15 percent of an equivalent shade-net or polyhouse area.

Adoption context

The system is widely used for off-season vegetable nursery raising, leafy greens, capsicum and tomato establishment in cool-season vegetable belts of Himachal Pradesh, Uttarakhand, Punjab, Haryana and the higher elevations of southern India. It also extends to nursery raising under hot conditions where partial shade and pest exclusion are valued.

Limitations

The fabric provides only modest temperature buffering compared to full polyhouse; it does not enable the year-round capsicum or cucumber production possible under naturally-ventilated polyhouses. UV degradation limits effective life to 2-3 seasons. Hoop frames must be replaced periodically. The system offers no protection against severe hailstorms or sustained heavy rain.

See also Polyhouse Shadenet Vegetable, Mulching Vegetables and Mulching Drip Floriculture.

References

  1. Agriculture Non-woven Fabric UV Treated Low Tunnel Fabric. Industry technical literature.