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March/April 2024 | Muedanyi Ramantswana

Precision irrigation in forest nurseries using the SUPA SCALE ® system

Forest Nurseries


Irrigation in the forest nursery is important because it ensures that plants receive water to facilitate growth. However, containerised forest nurseries traditionally rely on visual observations or intermittent time-based watering schedules which can lead to overwatering and water wastage. The process of overwatering can lead to anaerobic environments which are prone to poor root growth, root rot and other diseases. On the other hand, underwatering can impede seedling growth and in extreme cases lead to high plant mortality. The overall irrigation objective is to ensure that the plants receive the adequate water at the right time, all the time!

What is the SUPA SCALE ® system?
The SUPA SCALE ® system is an innovative patented technology which measures the tray weight to determine moisture levels, then wirelessly communicates real-time data from the nursery back to the pump station to ensure optimal hydration is supplied to the plants. What is unique about the system is its ability to group multiple scales for precise plant hydration, while considering important characteristics and variables such as:
• Tray type
• Substrate characteristics
• Seedling development stage
• Specific nursery area conditions

How the SUPA SCALE ® system works?
Each scale measures the moisture content based on its designated group of trays. By averaging out these readings, the system provides an accurate representation of the moisture levels across different areas (groups) in the entire nursery.

Basically, the SUPA SCALE ® system has the ability convert weight into moisture levels, considering crucial determining metrics. Therefore, through experimentation, growers can determine the optimal dry and wet weights for their plants. These values are then used as benchmarks, allowing the system to interpret the weight of a tray and deduce its moisture content.

This eliminates the guesswork from irrigation, ensuring that plants receive the optimal amount of water.

How the SUPA SCALE ® system enables proportional irrigation and automation
The SUPA SCALE ® system can control irrigation needs precisely based on the moisture levels determined from the weight. The benefits of this system are two-fold, firstly proportional irrigation is possible, if for example a group of trays are determined to be 60% saturated, the system can release enough water to bring that level up to the optimal 100% by proportionally controlling the flow of water. Secondly, switching the irrigation on or off can be automated because the system can also be set to turn on the water when the moisture level drops below a certain threshold and turn it off once the optimal saturation level is reached.

Other important information about the SUPA SCALE ® system
The SUPA SCALE ® system is an innovative system for forest nurseries and holds several other benefits such as:
• Easily adaptable e.g., compatible with T-rail systems, roller bench system, tabled and potted applications,
• Robust weight handling ability e.g., each scale can support up to 30kgs,
• Improve space optimisation and resource utilisation,
• Precise watering leading to a more conducive environment for healthier plants and higher yields.

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