Why do you cover potatoes at night?

Potatoes aren't typically covered specifically "at night" as a standard cultivation practice. Based on FAO, CIP and USDA sources, you may be thinking of several related potato protection methods:

Light Protection During Storage: Potatoes must be stored in dark conditions to prevent greening. When potatoes are exposed to light, they produce chlorophyll and accumulate solanine, a toxic compound that causes bitterness and can cause nausea, vomiting, and diarrhea. According to FAO and USDA data, proper storage requires keeping potatoes "in dark, cool conditions" to prevent this light-induced greening.

Cover Crops for Soil Protection: If you're referring to covering the soil around potatoes, cover crops are used extensively in potato production. The CIP (International Potato Center) and USDA research shows that cover crops like winter rye, oats, and hairy vetch are terminated 4-6 weeks before potato planting. These provide nitrogen fixation (60-120 kg N/ha from vetch), erosion control, and disease suppression. Maine studies found cover cropping increased potato yields by 10-15% while reducing nitrogen fertilizer needs by 30-50 kg N/ha.

Temperature Management: For processing potatoes, maintaining proper storage temperatures (7-10°C) prevents "cold sweetening" - the conversion of starch to sugar that darkens fries and chips during cooking.

If you're asking about a specific regional practice of covering potato plants at night, that is not documented in the FAO, CIP or USDA sources we hold.