Soil & fertility
Keep greenhouse soil healthy, balanced, and disease-free
Adopt a proactive soil program that supports vigorous growth, maximises nutrient efficiency, and resets disease pressure between crops.
Proven soil mix recipes
| Mix name | Ingredients | Notes |
|---|---|---|
| Universal vegetable mix | 40% coconut coir, 30% compost, 20% perlite, 10% worm castings | Lightweight and moisture-retentive with gentle nutrients. Ideal for raised beds and containers. |
| Fruiting crop blend | 35% peat or coir, 30% compost, 20% aged bark fines, 10% perlite, 5% biochar | Improves drainage and cation exchange capacity for tomatoes, peppers, and cucumbers. |
| Propagation mix | 50% coco coir, 30% perlite, 20% vermiculite | Sterile, low-nutrient medium encourages strong roots for transplants and cuttings. |
Nutrient management fundamentals
- • Test soil or media quarterly for pH and soluble salts; adjust fertiliser plans accordingly.
- • Use slow-release or organic sources such as compost tea, fish hydrolysate, or balanced granular fertilisers.
- • Maintain pH between 6.0–6.8 for most crops; use dolomitic lime to raise pH or elemental sulphur to lower it.
- • Flush containers every 4–6 weeks to prevent salt buildup, especially when using fertigation.
Prevent soil-borne pests and diseases
- • Sterilise containers with a 10% bleach solution or hydrogen peroxide before reuse.
- • Remove crop residue promptly and compost it outside the greenhouse to reduce pathogen reservoirs.
- • Encourage beneficial biology with compost teas or microbial inoculants while maintaining airflow.
- • Rotate crops or switch container locations to interrupt pest and disease cycles.
Rejuvenate and rotate between crops
- • Between crops, remove the top 2–3 inches of media and replace with fresh mix or well-aged compost.
- • Solarise or steam soil to 190°F (88°C) for 30 minutes to knock back pathogens before seed starting.
- • Plant cover crops such as buckwheat or clover in unused beds to add organic matter and support beneficials.
- • Record nutrient inputs and yields to fine-tune future amendments.
Implementation checklist
- Standardise your soil mix recipe and document amendments for each crop cycle.
- Establish a testing schedule for pH and EC; log results alongside fertigation events.
- Plan crop rotations or container moves to prevent repeated planting of the same family.
- Allocate time between crops for sanitation, steaming, or solarisation as needed.
Frequently Asked Questions
How often should I replace greenhouse soil?
Refresh the top layer between crops and fully replace container mixes every 2–3 crop cycles, or sooner if disease builds up. Raised beds benefit from annual additions of compost and mineral amendments.
What is the best way to sterilise soil?
Steam soil to 190–200°F (88–93°C) for 30–40 minutes or solarise beds by covering with clear plastic for 4–6 weeks in summer. Avoid chemical fumigants in hobby greenhouses.
How do I prevent nutrient burn in containers?
Use diluted liquid feeds, monitor electrical conductivity (EC), and flush pots with clean water periodically. Switch to slow-release fertilisers if salt buildup is common.