Onion Yield and Storage Program: Global Grower Guide

By Ihumate

Harvested onion bulbs ready for grading

Table of Contents

Crop Background and Variety Selection

  • Match short-, intermediate- or long-day varieties to local latitude and the bulbing season. A poor daylength match causes premature or failed bulbing.
  • Choose locally proven, low-bolting varieties with resistance to downy mildew, purple blotch and pink root; align skin color and dry matter with fresh, dehydration or storage markets.

Soil Preparation and Planting

  • Use full sun and fine, well-drained soil near pH 6.0-7.0. Test before planting and incorporate fully composted organic matter plus required phosphorus and potassium.
  • Sow about 0.6-1.3 cm deep, with rows roughly 30-45 cm apart, then thin to 7.5-10 cm. Avoid deep planting so bulbs can expand.

Nutrient Management

  • Base P, K and sulfur on tests. Split nitrogen during leaf growth, then reduce it as bulbs enlarge; late excess N produces thick necks, delayed maturity and poor storage.
  • Use humic acid root-zone conditioning in low-organic-matter or compacted soil. Amino acid nutrition and seaweed extract can support recovery after transplant, cold or heat stress but do not replace NPK.

When planning stage-specific nutrition, evaluate Potassium Sulfate SOP 0-0-52, Disodium Octaborate Tetrahydrate 20.5% B, Agricultural Amino Acid Liquid against soil and tissue tests, then set formulation and rate according to crop demand, local registration and field trials.

Irrigation Recommendations

  • Because roots are shallow, maintain even moisture, often near 25 mm per week after rainfall and evapotranspiration adjustments. Prefer drip irrigation and limit prolonged leaf wetness.
  • Stop irrigation when bulbs reach target size and about half the tops fall, allowing skins and necks to dry before harvest.

Pest and Disease Management

  • Monitor thrips with blue or yellow traps and leaf-sheath checks. Control weeds and excess N, conserve beneficials, and use locally registered neem or entomopathogenic fungi at low pressure.
  • Rotate for 3-4 years, plant clean material, improve airflow and drainage, and remove residues. Manage downy mildew, purple blotch, soft rot and root diseases from scouting data.

For preventive disease and rhizosphere IPM programs, evaluate BioShield Microbial Biocontrol Powder alongside rotation, field sanitation, pest monitoring and locally registered measures.

Harvest and Post-Harvest Handling

  • Harvest when about 50% of tops have fallen and begun drying. Avoid wet harvest and neck damage; remove injured, thick-necked and diseased bulbs.
  • Cure for 2-4 weeks in warm, dry, well-ventilated conditions. Grade only after necks and skins are dry, then store cool, dry and ventilated without freezing or condensation.

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