Types of benches and containers used in Polly houses

 

Benching:

If you intend to grow pot plants in a greenhouse, you probably need some benches. Benches enable you to raise plants off of the greenhouse floor, keeping them away from disease and often in better light. A tiered system of benches usually provides more useable space than if you were to only use the floor. Benches can be made out of metal, wood or plastic, and are usually either slatted or solid in construction. The surface of a bench should drain freely. Wooden benches if not treated with preservative can rot and may become infested with pests such as ants or mealy bug. Capillary matting (i.e. a continually moist, absorbent material, sold by some greenhouse companies) will help reduce the need for watering if used on a bench, to sit pots on.

The duration of crop in greenhouse is the key to make the greenhouse technology profitable or the duration of production in greenhouses should be short. In this context, use of containers in greenhouse production assumes greater significance.

The containers are used for the following activities in greenhouse production.

• Raising of seedlings in the nursery

 • Growing plants in greenhouses for hybrid seed production of flowers

 • Growing plants for cut-flower production.

• Growing potted ornamental plants.

 

Advantages of containers in greenhouse production

• Increase in production capacity by reducing crop time.

• High quality of the greenhouse product

• Uniformity in plant growth with good vigour.

 • Provide quick take off with little or no transplanting shock.

• Easy maintenance of sanitation in greenhouse

 • Easy to handle, grade and shift or for transportation.

• Better water drainage and aeration in pot media.

• Easy to monitor chemical characteristics and plant nutrition with advanced irrigation systems like drips.

Advantages and disadvantages of different plant growing containers

Containers	Advantages	Disadvantages
Clay pot	Low cost Easy water management	Slow to work with pots and dry out fast They are heavy to handle
Fiber block	Easy to handle	Slow root penetration Short life
Fiber tray	Minimum use of space	Hard to handle when wet
Single peat Pallet	No media preparation Low storage requirement	Requires individual handling Limited sizes can be handled
Prespaced Peat pallet	No media preparation Limited to small sizes
Pot	Easy to handle in field Available (square / round) in large sizes	Difficult to separate Pot
Single peat	Good root penetration
Strip peat pot	Good root penetration	Slow to separate
Protrays	Easy to handle Reusable	May be limited in sizes
Plastic pack	Easy to handle	Roots may grow out of container
Plastic pot	Reusable Good root penetration	Requires handling as single plant
Polyurethane foam	Easy to handle Requires less medium Reusable	Requires regular fertilization
Soil band	Good root penetration	Requires extensive labour
Soil block	Excellent root penetration	Expensive machinery
Perforated	Easy to handle	Requires regular fertigation
Plastic tray	Requires less medium Available in many sizes reusable	Roots may grow out of the container
Perforated	Less expensive	Less durable
Polyethylene	Reusable bags	Requires less storage space

 

Selection of suitable containers depends upon the crop to be produced in greenhouse, plant characteristics like crop stage, duration, vigour, growth habit, root system, etc. Generally long duration, deep rooted and vigorous crop plants require bigger containers compared to short duration, shallow and less vigorous ones. The containers provide optimum condition for germination of seed and growth and development of transplants. 

23.2 BENCHES

23.2.1 Floor as benches

Growing plants directly on the floor in conjunction with ground floor heating systems using the floor for growing plants is gaining popularity, but the cement must be laid exactly level in order to achieve an even distribution of water when flooding floors. Porous concrete floors may be expanded in width to serve as “benches”. The main advantage is the porosity offered and the lowered cost from bypassing above ground structures. This system works well for some species. However, the added fatigue on employees may not be worth the initial savings when considering the strain of working at an awkward position.

23.2.2 Raised Benches

23.2.2.1 Bench arrangements

Maximum utilization of growing facilities is largely based on the amount of growing area achieved. Benches in the peninsular design may result in a greater growing area than if they were in a longitudinal arrangement. The peninsular design also allows many species to be conveniently segregated, which can be a real advantage for retail growers. However, many growers have found routine tasks such as watering much easier on longitudinally placed benches.

Lastly, non-stationery benches, which provide even more growing space, are gaining popularity with growers. Movable benches (fig 23.2.2), known as rolling benches, can increase efficiency up to 90 percent of the floor space. Bench platforms are moved by a crank at the end of the bench from side to side. Some can be moved by hand by sliding the benches over the top of long steel poles. Aisles are created where the grower wants to work at any given time. Rolling benches are easy to move by practically any labourer, which is an added bonus. Movable benches, however, are not appropriate in a retail setting or where plants must be accessed frequently. Retailers are better served by staying with conventional benches such as the longitudinal, peninsular, or other comparable type designs.

23.2.2.2 Bench Space Efficiency

Benching efficiency is defined as the square feet of bench space to the entire greenhouse floor area. This number is expressed as a percentage.

Examples: A grower chooses a longitudinal bench arrangement in a greenhouse 30' x 80' or 2400 square feet of floor area. He decides to use 3-foot wide benches and 2.5-foot wide aisles and allows four feet at the end of the benches. The greenhouse has a benching efficiency of [5 (number of benches) x 72 (length of each bench) x 3 (width of bench)] \ (30 x 80 greenhouse dimensions) x 100 = (1080/2400) x 100 = 45%.

However, if the benches were widened to four feet and 74 feet long, allowing a three-foot turn around rather than four feet as before, efficiency could be increased to 49 percent [(4 x 74 x 4) / (30 x 80) x 100 = 49%]. To further increase efficiency, the benches could be widened and the aisle widths reduced.

If the grower looks at the same greenhouse with 2400 square feet floor space, but this time designs a peninsular bench arrangement, he will find that the peninsular design will increase the growing area even more. Still greater efficiency could be realized with rolling benches.

23.2.2.3 Bench Design

An alternative to conventional benching systems is the ebb and flow (flood or sub irrigation) benches (fig 23.2.3). Metal or wood benches are replaced with watertight, molded plastic trays. Trays are periodically flooded with water and desired fertilizer concentration, which can be taken up throughout the plants via capillary action. This system has such advantages as reduced and uniform applications of water and fertilizer. Excess water and fertilizer are collected after each flood and drain cycle to be recirculated later. Up to 50 percent reductions in water and fertilizer savings have been reported. Labour costs will also be reduced since the entire bench can be watered at the same time. This may not be feasible if plants with dissimilar water requirements are grouped together on each bench. An added benefit is that foliage will stay dry and plants can be grouped closely for greater production efficiency. Ebb and flow bench manufacturers have also designed trays to be incorporated into a rolling bench system for even greater versatility. This bench system should be given serious consideration with ever increasing restrictions on water and fertilizer runoff.

23.2.2.4 Materials for Benches

23.2.2.5 Wooden Benches

Locust, cedar, redwood, and cypress are all woods highly resistant to decay. Paint benches before use with copper naphthenate or other preservatives to augment the natural decay resistance of the wood chosen. When redwood is chosen, iron and steel will corrode from naturally present decay inhibitors. Therefore, choose metals such as aluminum, zinc, or brass nails, screws, and bolts. Benches may be all wood or in combination with a different material for the base. Often, expanded metal or welded wire of one inch or smaller mesh is used. While expanded metal is more expensive, it does not sag like welded wire. Besides decay, wood may warp and often absorbs soils, chemicals, etc. which cannot be adequately removed. When wood is chosen, higher maintenance will be required on a regular basis.

23.2.2.6 Concrete

Some growers built concrete forms and pour entire benches, including the legs (supports), all at once. These benches are permanent and do not allow for change later. Concrete benches are durable and will not require additional treatment to prevent decay such as with wood. They may be reinforced with steel rods, when poured, for additional durability. Lastly, consider drilling holes in the base of the bench for proper drainage.

23.2.2.7 Metal

Entire metal or steel benches are used alone or in combination with another material. Advantages of galvanized metals over wood are the longevity and resistance to rot and decay. Metal benches may be expensive to install initially, but can be considered a one-time cost. Also consider the lowered maintenance costs when these types of benches are used.

23.2.3 Temporary/Portable Benches

23.2.3.1 Plastic

          Although plastics are becoming more common for bench beds, plastic frames are not always desirable. They are often not as durable or able to support as much weight as other benching materials. However, in a retail setting, prefabricated benches can be purchased which are lightweight and, thus, portable. These are also available mounted on rollers, making them particularly convenient in retail settings. Also, maintenance on plastic benches is again considerably less than for wood

23.2.3.2Pallets

Another portable bench system can be inexpensively constructed by placing pallets on cement blocks for support. Besides the low cost, this portable display can be easily and quickly disassembled.

 

23.2.3.3 Bench Supports

Cement blocks are commonly used to support bench tops, particularly if they are not intended to be permanent. Permanent benches may also be supported in this fashion. Additionally, steel poles are often used for bench support. Plastic bench supports are becoming more popular, but again they are often not as strong, and in many cases are most appropriate for temporary retail displays. When wooden supports are used, it is especially critical to chemically treat them for decay, at least the area which will be submerged in the soil. The same preservatives which may be used on the growing surface of the benches are appropriate. Also, by pouring concrete footings, the structural integrity of the bench supports may be reinforced.