Introduction
Greenhouse irrigation supplies water (and commonly nutrients) in a controlled way to meet plant needs while limiting waste and disease pressure. Different systems are chosen based on crop type, growth stage, greenhouse design, water quality, labour and budget. Effective greenhouse irrigation improves water-use efficiency, crop uniformity and product quality.
Major Irrigation Systems
1. Drip Irrigation (Surface and Subsurface)
How it works: Water is delivered slowly and directly to the root zone through pressure-compensating emitters, driplines or micro-tubing. Subsurface drip places lines below the medium surface while surface drip sits on top of the substrate.
Advantages: high water-use efficiency, precise water and nutrient placement, easy integration with fertigation, lower foliage wetting (reduces foliar diseases), and good automation potential. :contentReference[oaicite:1]{index=1}
Limitations: higher initial cost, susceptibility to clogging (requires filtration), and complexity when using buried laterals.
2. Subirrigation / Ebb & Flow (Flood & Drain) Benches
How it works: Benches or trays are periodically flooded with nutrient solution which then drains back to a reservoir for reuse or disposal. The crop draws moisture from below, keeping foliage dry.
Advantages: water and nutrient recycling, uniform wetting of media, reduced foliage wetting (lower disease risk) and good suitability for many potted ornamentals and some vegetables. :contentReference[oaicite:2]{index=2}
Limitations: requires leak-proof benching, careful reservoir management (filtration and sanitation) and good drainage design to avoid stagnation or pathogen spread. :contentReference[oaicite:3]{index=3}
3. Overhead Sprinklers, Misting and Fogging Systems
How it works: Water is sprayed from above using sprinklers, booms, misters or foggers. Misting and fogging create fine droplets for propagation and microclimate control.
Advantages: useful for propagation, rapid coverage, and microclimate control (cooling and humidity increase). Helpful for seedlings and cuttings that need high humidity.
Limitations: wets foliage (increasing disease risk), lower water-use efficiency than drip/subirrigation, and requires good water quality and pressure for fine nozzles. :contentReference[oaicite:4]{index=4}
4. Capillary Mat Systems
How it works: Pots or trays sit on an absorbent mat that wicks water from a reservoir. Plants draw moisture upward through their media by capillary action.
Advantages: uniform moisture delivery for many small pots/seedlings, simple operation, lower labour and reduced evaporation and foliage wetting. :contentReference[oaicite:5]{index=5}
Limitations: risk of algae/pathogen build-up on mats if not cleaned, need consistent reservoir management, and limited suitability for large single plants or crops with very different water needs on the same mat.
5. Soilless Substrates & Grow Bags with Drip Stakes
How it works: Crops are grown in inert or soilless bags (cocopeat, perlite mixes, rockwool etc.) and irrigated with drippers or stakes inserted into the substrate for even wetting.
Advantages: excellent control over root environment and nutrition, cleaner product, reduced soil-borne pests and high suitability for high-value greenhouse vegetables and cut flowers. :contentReference[oaicite:6]{index=6}
Limitations: substrate cost, need for frequent monitoring of EC/pH and water, and disposal or reuse logistics for media.
6. Sand Culture and Capillary Pipes
How it works: Plants are grown in sand or similar inert media with water supplied by capillary pipes or troughs that maintain steady moisture through capillarity.
Advantages: stable moisture for some specialty crops and compatibility with automated nutrient delivery.
Limitations: infrastructure costs, management complexity and requirement for clean water to avoid pipe clogging. :contentReference[oaicite:7]{index=7}
Typical Applications by Crop and Stage
| Crop / Stage | Preferred System(s) | Why |
|---|---|---|
| Vegetables (tomato, pepper, cucumber) | Drip (surface or subsurface); substrate + drip stakes | Precise water/nutrient supply, reduced foliage wetting and high water efficiency. |
| Floriculture (roses, gerbera, carnations) | Subirrigation benches, drip, mat systems for propagation | Quality-sensitive crops need stable root moisture and low foliar wetness. |
| Propagation (seedlings, cuttings) | Misting/fogging, capillary mats, ebb & flow benches | High humidity and gentle, frequent moisture are needed for young plants. |
| Nursery pots and multi-size containers | Capillary mats, drip, subirrigation | Different pot sizes and water-holding capacities require a system that maintains uniform moisture without over-wetting foliage. |
| Cut flowers in soilless culture | Substrate + drip stakes, sand culture | Clean product and precise fertigation for high-value production. |
Design and Management Considerations
- Water quality and filtration: Essential for drip and fine spray systems to prevent nozzle/emitter clogging. Use appropriate filters and regular maintenance. :contentReference[oaicite:8]{index=8}
- Uniformity and pressure control: Ensure uniform emitter spacing, pressure-compensating devices or pressure regulation for even distribution across the greenhouse. :contentReference[oaicite:9]{index=9}
- Humidity and foliage wetness: Minimize regular foliage wetting to reduce fungal disease; use subirrigation or drip where possible. :contentReference[oaicite:10]{index=10}
- Automation and sensing: Soil/substrate moisture sensors, timers and fertigation injectors improve water- and nutrient-use efficiency and reduce labour. :contentReference[oaicite:11]{index=11}
- Drainage and recirculation: Systems that recirculate (ebb & flow, flood floors) need careful pathogen control, filtration and monitoring of EC and pH of nutrient solution. :contentReference[oaicite:12]{index=12}
- Economic & labour factors: Match system complexity to the scale and value of the crop; automation reduces labour but increases capital and maintenance needs.
Summary — Choosing the Right System
For most greenhouse vegetables and high-value crops, drip irrigation combined with good fertigation practice is the most water- and nutrient-efficient choice. Subirrigation (ebb & flow) and capillary mats are excellent where foliage wetting must be avoided (ornamentals, potted plants, propagation). Overhead misting and fogging remain indispensable for propagation and microclimate control but should be used with disease management in mind.
References & Further Reading
- Greenhouse Best Management Practices — Irrigation Systems, University of Massachusetts. :contentReference[oaicite:13]{index=13}
- Drip irrigation guidance and system components (Netafim — Drip Irrigation PDF). :contentReference[oaicite:14]{index=14}
- Ebb-and-Flow (flood & drain) system overviews and bench designs. :contentReference[oaicite:15]{index=15}
- Capillary mat and misting system summaries (Greenhouse Management, manufacturer and grower resources). :contentReference[oaicite:16]{index=16}
- Fertigation and drip integration overview. :contentReference[oaicite:17]{index=17}
