NFT Sliding Bench Systems (Moving Gully System)

An NFT (Nutrient Film Technique) Sliding Bench System (A.k.a Moving Gully System or Mobile Gully System (MGS)) is the most efficient user of greenhouse space for any type of NFT system.

They require a minimum of two workers to operate the systems and it is very easy for staff members to plant, harvest and clean the system.

An NFT Sliding Bench System is especially suitable for growers who wish to grow one variety of plant such as lettuces, and for those who wish to maximise available greenhouse space as much as possible.

In a typical Sliding Bench NFT system you can grow approximately 20.5 plants per square metre of greenhouse area (including pathways around the bench) or 26 plants per square metre excluding pathways.

Growers can expect to achieve a minimum of 8 crops per year in the NFT Sliding Bench system based on a good sized lettuce sold by weight.

13 – 14 crops per year can be achieved for either a smaller size lettuce sold per head, or if a larger media volume was used to enable the seedlings to be kept in the nursery area for a longer period.

The crops per year figure is based on time in the NFT system only I.e. from the time the seedling is transplanted into the NFT system and harvested.

Time in the nursery area is excluded as it is a separate entity from the main system.

Companies who claim to sell hydroponic lettuce systems that achieve much higher crop rotations than 14 crops per year would either grow their mature lettuces to a small size or they have a much larger media volume than normal to allow the seedlings to develop to a larger size before entering the main growing system. Quite often they will have a larger than normal area dedicated to nursery production or they will have an intermediate system between the nursery and the main NFT system. This allows seedlings to be kept longer, to a much larger size prior to entering the main NFT system and thereby the time in the main NFT system is shorter, allowing more crop rotations per year in the NFT system. Such systems can be quite labour intensive as they involve a lot of double handling and risk of root disturbance and damage. It also requires quite a lot of additional greenhouse space which can be expensive.  The cost of using a larger growing media volume can also be uneconomical for lower value crops. A well designed NFT system is a very high performance growing system. You would struggle to find a competing system that offers a shorter growth time in comparison.

Pure Hydroponics supports a 2 stage growing system. Seedlings are raised in an Ebb and Flow propagation system. Then when the seedlings are ready for transplanting they are transplanted into the main NFT system. The root system is therefore only disturbed once before harvest.

 The key aspects of the NFT Sliding Bench system are as follows:

  • It has the highest yield per m2 of greenhouse space for any type of  NFT system.
  • It is a manually operated system requiring two workers to plant, harvest and move the gullies.
  • The nutrient solution is recirculated through the pump room and automatically dosed and re-oxygenated.

The NFT Sliding Bench system is operated as follows:

  • The system comprises of one continuous steel framed support bench running the length of the greenhouse with pathways on all four sides.
  • NFT gullies are then placed onto the bench and spaced according to the growth stage of the crop.
  • Seedlings are typically propagated in 25x25x40mm Rockwool cubes or media filled cell trays or pots in an Ebb and Flow plant propagation system. The seedlings are then transplanted into 100x50mm Pure Hydro NFT gullies.
  • Gullies containing young plants are then introduced at one end of the sliding bench (the planting end). These gullies are then gradually moved along the bench and spaced further apart as the plants mature.
  • By the time the gullies reach the other end of the bench (the harvesting end) the plants are ready for harvest.
  • A sanitation system in the pump room (e.g Oxine or Ozone) targets any pathogens which may be introduced into the mixing tank.
  • On harvesting days, the gullies containing mature lettuces that are ready to be harvested are removed from the sliding bench at the harvesting end of the bench. Two workers are then required to move the remaining gullies along the sliding bench to fill the vacant space left by the harvested gullies.
  • This process fills the gaps left by the harvested gully and allows room for newly planted gullies to be introduced to the sliding bench.
  • The harvested gullies are then taken out of the greenhouse, cleaned and sanitised and then replanted and introduced at the planting end – allowing the next crop cycle to begin.
  • A Bluelab Pro Controller dosing control system is used to monitor and control the nutrient and pH levels in the NFT system mixing tank.
  • The Bluelab Pro Controller  control system uses Triple Peristaltic Pumps to dose nutrient stock solution and pH corrector into the mixing tank.
  • The nutrient solution flowing from the NFT gullies is collected in the catchment system of the sliding bench and directed to a return line which gravity feeds back to the pump room for recirculation.
  • An oxygenation system will ensure there is an abundant supply of dissolved oxygen at all times in the nutrient solution.
  • Growers can steer the crops to be more vegetative or generative or to have hard or soft foliage by adjusting the nutrient strength (EC) of the nutrient solution.

Pure Hydroponics can design and supply full Sliding Bench systems to fit an existing greenhouse or we can supply a turn-key system comprising of an NFT Sliding bench system, greenhouse and climate control.

For growers located in distant countries we also offer a shopping list and design service which allows growers to source PVC pipework and common equipment locally and Pure hydroponics supplies the specialist equipment only such as NFT gullies, dosing control system and NFT system accessories. This keeps freight costs down for the grower and can make the overall project more affordable.

Please contact Pure Hydroponics for a per square metre estimate for an NFT Sliding Bench system or a quotation for our Design and Shopping List service.

All interested parties must complete the attached Commercial Design Questionnaire as part of their enquiry.

Commercial System Design Questionnaire