How should I prepare soil for onion planting?
Written by
Tina Carter
Reviewed by
Prof. Charles Hartman, Ph.D.A successful onion planting begins below the surface, under the ground. I found that out after having a disappointing harvest from the unamended clay soil I had. I now give priority to achieving the loamy texture - a 3-part native soil and 1-part compost mixture. I also tested the pH level at 3 different locations in my bed plot - the variations surprised me in my 10x4ft (3x1.2 m) plot!
Soil Composition
- 2-3% organic matter - use decomposed leaves or manure
- Screen soil through 1/4-inch (6 mm) mesh to remove rocks
- Clay soils: Add 2 inches (5 cm) sharp sand per 12 inches (30 cm) depth
pH Balancing
- Target 6.0-6.8 pH - test with digital meter
- Add lime at 1 lb/100 sq ft (0.45 kg/9.3 m²) if below 6.0
- Lower pH with sulfur pellets if above 6.8 - 0.5 lb/100 sq ft (0.23 kg/9.3 m²)
Drainage Fixes
- Build 8-inch (20 cm) raised beds for wet areas
- Mix in 30% perlite for container soils
- Slope beds 2% grade - 1 inch drop per 4 ft (2.5 cm per 1.2 m)
Drainage determines the health of a root. One year, the worst rot we experienced, was in a level garden that received record amounts of rain. I now try to always plant on 8-inch (20 cm) mounds sustain 12-inch (30 cm) spacing. For containers, drill 5 more holes - you can still keep the soil from spilling out by lining them with coffee filters.
Preliminary soil tests should be performed weekly. A low-cost ($15), moderately accurate probe that measures moisture and pH works for the sake of prepping soil. Soil amendments should be allowed to settle for 10 days before planting is performed. Walking on beds compacts the soil; therefore, it is best that paths between rows be 2 feet (60 cm) wide. Your onions will thank you with crisp layers.
Read the full article: When to Plant Onions: Expert Guide for Perfect Bulbs
