What soil conditions optimize kale growth?
Written by
Paul Reynolds
Reviewed by
Prof. Martin Thorne, Ph.D.Kale does best in well-drained soil with a pH of around 6.0 to 7.5 for optimal nutrient uptake. This range will ensure that you don't suffer lockout of minerals such as nitrogen and phosphorus that kale is eager to extract from the soil. I test my soil every year in my garden and add lime where needed. Taking these steps ensures you won't have to deal with diseased and stunted plants.
Organic Matter Enrichment
- Compost: 2-3 inches per 100 sq ft (5-7 cm per m²)
- Timing: Work into top 8 inches (20 cm) before planting
- Frequency: Reapply each season
- Benefit: Improves water retention and microbial activity
Mineral Balancing
- Acidic Soil: Apply 5 lbs lime per 100 sq ft (2.3 kg per 9 m²)
- Alkaline Soil: Add sulfur per soil test results
- Nutrients: Incorporate 5-10-10 fertilizer at planting
- Monitoring: Test pH every 6 months
Drainage is critical for healthy roots. When kale is waterlogged, it tends to rot. I add perlite to heavy clay soils at a rate of 30% by volume. For containers, I use potting mix with added perlite. I also create raised beds in areas with poor drainage. Make sure to monitor, especially after a few days of heavy rain.
Test the soil pH with inexpensive kits or a meter. I take samples from different spots to a depth of 6". Adjust gradually over a few weeks, not days. Too much lime can make some micronutrients unavailable, so apply it when soil moisture conditions are uniform (expect it to rain occasionally).
Basic Mix
- Base: 50% quality potting soil
- Compost: 30% well-rotted organic matter
- Drainage: 20% perlite or vermiculite
- Fertilizer: 1 cup 5-10-10 per 5 gallons
Maintenance
- Top-dress: 1 inch compost monthly
- pH Check: Every 60 days
- Aeration: Loosen crusted surface weekly
- Refresh: Replace top third annually
Provide balanced nutrition to plants at all stages of growth. Compost tea should be applied every four weeks when plants are actively growing. I also side-dress with aged manure during the middle of the growing season. Avoid using fertilizers that are heavily high in nitrogen, as this can create lush, leafy growth but sacrifice flavor and hardiness.
Read the full article: When to Plant Kale: Expert Timing Guide
