The type and placement of benches that is used in a greenhouse depends on the crops that will be grown in the greenhouse. If cut flowers are to be grown, the plants will be there a long time and the only thing that will be moved out is the flowers which are very light. If vegetables were to be grown, the same general things would be true. If potted plants were to be grown, then many pots would have to be moved in m stay a short time and be move out. Materials handling would be an issue. If customers will be in the house, there must be plenty of space for them to move around.
Bench vs. Bed
¥ A bed is where boards are laid out as sides and the native soil or soil mix is laid over the native soil.
1. Easy and cheap to install
2. Easy to work
3. Easy to water and stays uniformily moist
1. Difficult to pasteurize- steam will not penetrate down into soil for enough.
2. Under laying soil may not drain too well.
3. Soil may be too cool for good crop growth.
¥ A bench is where the bottom physically separates the soil mix from the native soil.
1. Easy to steam (Pasteurize)
2. Reintroduction of pathogens is slow
1. Dries out more quickly
2. More expensive to construct
Raised vs. Ground
¥ A ground bench is where the top of the bench is no more than 12" from the soil surface. The primary advantage of the ground bench is the large amount of head room for tall growing crops. For potted crops to be grown on a ground bench would mean an excessive amount of bending meaning sore backs.
¥ A raised bench is where the top of the bench is between 24 and 36" (book says 32-36 fpr pot crops) above the soil. Generally used for potted plants and low growing cut flowers so that there is less bending.
¥ Longitudinal - benches run the length of the greenhouse. Traditionally these benches have been filled with soil and used for cut flower or tomato production. This arrangement is efficient for watering, sterilization and harvesting of cut flowers. The isles tend to be very long which means lots of walking. With cut flowers you can carry many flowers in one trip whereas with potted plants you would be forced to make many trips. The efficiency of floor space utilization is in the 63-66% range.
¥ Peninsula - benches run the width of the greenhouse. Most frequently used for potted plants because the distance to carry the pots is reduced compared to the longitudinal. The material that the bench is made of could be important. Air movement around the plants is important so that a bench type that allows air movement reduces disease development. Common types or expanded metal (expensive) or snow fence (doesn't last). Percent of floor utilization is 75-80%. Movement of pots to and from bench requires a lot of labor so various mechanical devices to assist in flow of plants have been devised. First is the wheeled cart, preferably with multiple shelves. Some can be attached to a cart and some are designed to be used alone. There are some carriers designed to travel on tracks over the plants. The problem is that the track is expensive to buy and install. Moving belts are the way that many plants are moved today in the larger greenhouse ranges,
¥ Island--These are raised benches that permit someone to walk all the way around the bench. The major problem with this type of bench is the poor amount of floor area covered, 56-60% covered. For this reason this type is most frequently used for a sales area for customer convenience.
¥ Tiered Benches--Grow high light plants on the top shelf and low light plants on the lower shelf. Sometimes lights may be placed under the top shelf to provide additional light to the crop on the second shelf. Draining of water may be a problem since you don't want the excess water from the top shelf to wet the plants on the lower shelf. Disease control. Often tiering is used for seed germination as long as lights are used.
¥ Ferris Wheel--Increase available growing space. Sold commercially as Roto-Shelf. Eight benches attached to a large wheel that constantly rotates. Light available to the plant and plant height are the factors which limit its use. It has been used successfully with African violet. It is possible to save around 30% of growing cost by this technique.
¥ A-Frame for either pots or hanging baskets.--This technique permits the use of more vertical space but still permits good light penetration to each plant. This works very well with hanging baskets but can also be made to handle pots.
¥ Sliding benches--The objective is to increase the percent of floor covered by plants. One type is called the aisle/eliminator. Longitudinal benches are placed on rollers so that they can be rolled back and forth thus eliminating all aisles except 1. It is necessary to have 1 aisle for every 5 benches. With this technique the amount of floor covered can be increased to up to 90% or a bit higher.
¥ Mobile or Moving Benches--Objective is to locate work force centrally and move the plants too and from the work force. This type generally has e movable tray where the whole tray is moved to the work area and all the work is done at that location. With this type of system the placement of the trays must be carefully made so that you don't have the tray you need all the way at the back and have to move all the trays to get to it.
¥ No bench--In most instances where no bench is used the pots or flats are placed on a solid surface like porous concrete. The advantages are that the plants can be placed in any pattern desired with no worry about benches. The biggest disadvantage is that the people working on the crops must be bent over to pick up, put down or work on a plant. This system is most widely used for bedding plants where manual labor on the plants is minimal. The plants are moved in, grow, then moved out.
Efficiency of Space use
Longitudinal--If the greenhouse is 35 X75 it contains 2625 sqft. If benches are 3 feet wide and the aisle is 28 inches with 3 feet at the end of the bench the efficiency is 47%. Just changing the aisle width from 28 inches to 18 inches increases the percent of usable area to about 55%. If the benches are 4 feet wide and the asile is 18 inches the efficiency is 63%. If the bench is increase to 5 feet wide then the efficiency is increased to 68%.
The bottom line is that the benches should be as wide as possible and the aisle as narrow as possible to get maximum space utilization.