Choosing the Right Greenhouse Irrigation System

7 Greenhouse Irrigation Systems

By Guillermo Maldonado, Grower Advisor

Irrigation is one of the most important controllable aspects of growing and could have a major impact on the quality of the crops. How then to decide which irrigation system is the best suited to our needs? The answer isn’t always simple and will depend on several factors: type of crop, climate, labor, initial investment, growing media and type of soil, container size… Here are some pros and cons of some of the most common irrigation systems to help you to make the right choice.

Irrigation System n^o1

Manual Irrigation

PROS	CONS
Low initial investment (inexpensive equipment) Catered irrigation (only the crops that need water get water)        – Good opportunity to inspect the crops.	Can be inefficient and uneven;        – Requires training and experience; Time-consuming task (more labor); Hard to keep crop’s canopy dry; Can have an impact on the soil structure If the flow isn’t adjusted properly; Can be wasteful and hard to apply fertilizer evenly; Can’t be automated.

Don’t Forget to…

• Inspect plants before irrigation; feel the weight. Remove the container and touch the media. Don’t only base your decisions on a quick visual inspection;
• Avoid overflowing the container or using high pressure nozzles as it disrupts the soil structure; certain aggregates will migrate to the top while the fines will settle at the bottom of the container, reducing overall drainage and affecting the dry down cycles;
• Flush lines before irrigating to ensure the appropriate water or fertilizer solution is applied on all crops;
• Make sure equipment and nozzles are adjusted to get the right flow and droplet size for the type of crop and container size.

Irrigation System n^o2

Sprinkler/Micro Spray Systems

PROS	CONS
Can be timed and automated; Can be used for a specific crop where low air humidity is an issue; Can be used to impact micro-climate around the plant and canopy; Medium to low initial investment.	Less efficient and wasteful if not managed properly; Uniformity can be a challenge; Low efficiency on dense canopies (may result in excessive runoff).

Irrigation System n^o3

Drip Irrigation

PROS	CONS
Can be automated and programmed based on many different inputs; Crop canopy remains dry (reduces incidence of foliar diseases); All the water is applied to the media:        – Can apply precise amounts of water which can reduce water usage;        – Water has a better distribution through the media; Water can be collected, treated and reused.	Medium to high investment; Water distribution can be problematic if growing media becomes too dry or drippers aren’t positioned properly; Cleaning and maintaining the system can be challenging; Further investments are required to collect, treat and reuse water (Gutters, collection reservoir, filtration system, UV system, …); If leachate is not collected, a lot of water can be wasted.

Irrigation System n^o4

Water Booms

PROS	CONS
Major reduction in labor costs; Can be programmed and automated; Can be used as a sprayer; Can be used to apply different types of products; Even coverage of the canopy; Excellent choice for large-scale monocrop productions.	High initial investment; Only possible for certain types of greenhouses; For better results, a trained operator is required to adjust equipment and carry out preventative maintenance; Difficult to manage with smaller batches of different crops at different growth stages. Easier to manage and better results with a uniform, high-quality growing media

Irrigation System n^o5

Sub-Irrigation- Ebb & Flow (for hydroponics systems)

Irrigation System n^o6

NFT – Nutrient Film Technique (for hydroponics systems)

Irrigation System n^o7

Mist Fogging

PROS	CONS
Ability to apply high volumes of water though very fine droplets; Most suitable option for germinating chambers/rooting stations; Effective impact on air humidity and climate in the greenhouse/growing area.	Medium to high initial investment;        – Higher when we include the costs of a germination chamber Requires an extremely efficient filtering system; Must install a high pressure line.

Whichever irrigation systems you choose, preventative maintenance is always recommended.  Make the proper adjustments when cycling through different seasons, crops and growth cycles.  Be pro-active and implement the best practices to ensure the healthy growth of your crops.