Feeding & Fertilizing Potatoes for Big Yields

Potatoes are hungry plants, and the right feeding regime can make all the difference between a disappointing yield and a bumper crop of delicious spuds. Here’s how to give your potatoes the nutrients they crave at every stage.

Feeding At Planting

• Compost or Manure:
  Mix well-rotted compost or manure into the soil or the bottom of your trench/grow bag before planting. Avoid fresh manure, which can cause scab and burns.
• Balanced Fertilizer:
  Use a general-purpose fertilizer (like 10-10-10 NPK) sprinkled at planting—follow the package directions for quantities.

Ongoing Fertilization

• Starter Feed:
  When shoots appear, apply a balanced granular or slow-release potato fertilizer along the rows or around containers.
• During Early Growth:
  Once plants are 15–20cm (6–8 in) tall, feed with a high-nitrogen fertilizer for leafy green growth.
• Tuber Formation:
  As potatoes begin to flower (signaling tubers are forming), switch to a feed with more potassium (K) and less nitrogen—this bulks up the potatoes.
  • Sulphate of potash or a tomato feed is ideal at this stage.

Feeding in Containers or Bags

• More Frequent Feeding:
  Potatoes in containers need extra feeding. Use half-strength liquid fertilizer every two weeks after shoots appear through flowering.

Organic Feeding Options

• Comfrey or Nettle Tea:
  Liquid feeds made from soaking comfrey or nettles are rich in potassium and other nutrients.
• Wood Ash:
  A handful worked into the soil supplies extra potassium but use sparingly and only on non-acid soils.

Signs of Nutrient Problems

• Pale/Yellow Leaves: Likely a nitrogen deficiency—give a nitrogen feed.
• Poor Tubers: Lack of flowers or small potatoes may signal potassium shortage—boost potash.

Tips for Success

• Don’t over-fertilize—especially with nitrogen late in the season, which causes lush leaves but small tubers.
• Water after feeding to get nutrients to the roots and avoid “burning” plants.