Improving Labor Efficiency
Everyone strives for labor efficiency, whether operating agreenhouse alone or with the help of many employees. A good starting point inevaluating labor efficiency is to collect data on which operations require thegreatest amount of time. Transplanting, hand watering, plant selection forshipping and moving plants into and out of the growing area often use excessivelabor. Evaluate these first to see if improvements can be made.
Equipment is available for almost all the tasks that takeplace in the greenhouse, but not all tasks should be mechanized. This isespecially the case for the small grower because the initial capital outlay onsome of this equipment is very high.
Buying Guidelines
Before purchasing equipment or making changes to an existingsystem, consider the following basic concepts that apply to all businesses:
Keep things simple.Equipment or systems that you and your employees understand work best. Thesegenerally have fewer adjustments that need to be made, require less maintenanceand use standard parts.
Analyze your needs thoroughly. Equipment is expensive to own. Consider yourresources and what will give the greatest return to your business. For example,an automatic watering system that can be used year-round may be a better choicethan a precision seeder if you use it only 10 days a year.
Mechanize jobs that are repetitive, tedious ortime-consuming. Considerable equipment hasbeen developed for most of these jobs. Filling containers, spacing and movingplants, and watering are good examples of repetitive tasks that make sense toautomate.
Install equipment that reduces peak-period laborrequirements. The spring season andholiday shipping periods are usually the busiest. Carts or conveyors will moveplants quicker than hand carrying. You also reduce the need to hire and managemore employees.
Select equipment that will pace workers. Conveyor belts work well for potting, transplantingand packaging, providing uniformity and consistency. A variable-speed motoradjusts the belt speed for different operations.
Reduce the amount of walking that employees do. Walking adds considerable time to the cost ofplants. An average time to pick up or set down a flat of plants is 1.5 seconds.Carrying or walking can be figured at four feet per second. At an $8 per hourlabor rate, making a round-trip 15 feet away to place a flat of plants on abench adds about 2 cents to its cost.
Standardize your operations. Keep the number and types of containers that are used to a minimum toreduce inventory and the time needed to make changes to equipment. Wherepossible, ship in standard units such as carts or pallets.
Consider alternatives to purchasing equipment. Renting, leasing or sharing with a neighbor allowsthe use of equipment for short periods of time without a large investment.Consider purchasing pre-filled containers, plugs or pre-planted flats toeliminate the need for equipment and reduce peak labor needs.
Select equipment that is manufactured with standardparts. Delays in getting special partsmade to repair a down machine can interrupt a production schedule. Standardparts such as belts, drive chain, pulleys and sprockets can frequently be foundlocally.
Workstation design. Aworkstation is an area where an employee does a series of repetitive tasks suchas transplanting, potting or preparing plants for shipping. The layout of thisarea can have a large influence on efficiency. A good layout, where everythingis within easy reach, can decrease needed labor by as much as half.
A good transplanting rate for 48-cell flats is 20-25 flatsper hour. Based on an $8 per hour labor cost, the cost of transplanting 10flats per hour is $0.80 per flat, 15 flats is $0.53, 20 flats is $0.40 and 25flats is $0.32.
The top of the table should be at elbow height. Adjustmentshould be provided for different-height workers. It is best to provide for bothstanding and sitting positions as greater efficiency is achieved when workerschange positions.
The reach from the normal armrest position to get materialsshould be limited to a 24-inch radius to the side and front for women and 27inches for men. Á The work area is best if within 16-24 inches of theresting elbow position.
A workstation space of 3 x 3 feet is adequate for mostoperations. Space to the rear and sides can hold pre-filled containers, a cartfor placing transplanted containers and movement of the worker. Adequatelighting of 40-60 foot-candles over the work area will increase productivityand reduce eyestrain. Where multiple stations are employed, a belt conveyor tothe front of the workers will carry the completed containers to an area wherethey can be loaded for transport to the growing area.
An alternate workstation is a movable transplanting tableplaced in the greenhouse next to the growing area. The table is moved as thegreenhouse is filled. Pre-filled containers can be supplied on pallets near thework area.
Carts and wagons.The use of carts can speed up handling and reduce labor needs. One person canpush a cart loaded with 40-60 flats from an efficient transplanting area to thegrowing area.
Select a cart that has large wheels. Tire size should be atleast two inches wide and six inches diameter for use on paved floors and 2 3/4inches wide and 10 inches diameter for use on unpaved areas. One that has fixedcasters at the center of the cart with a swivel caster at the center of eachend will allow the cart to be turned within its own length.
The cart shelves should be made of a lightweight materialthat is strong enough to carry the load without sagging. A smooth metal orplywood shelf allows easier loading than a wire mesh material. Shelves shouldbe removable and adjustable for different-size plants.
There are many types and styles of wagons for greenhouseuse. Most have pneumatic tires for transport over unpaved surfaces. Thestandard wagon has a fixed rear axle and pivoting front axle on a fifth wheel.Where wagons will be used in tandem in narrow aisles, select a tracking designwhere both axles are connected together and one wagon will follow in the tracksof the other.
When the distance between the work area and the greenhouseis greater than 200 feet, carts and wagons should be pulled in tandem inmultiple units to save time. An electric cart or garden tractor can provide thepower.
Conveyors. Analternative to carts is a trolley conveyor. The system consists of a tubular orangle track suspended from the greenhouse or headhouse frame and atrolley-mounted rack that is pushed along manually. Suspending the track overthe benches and plants means that no additional aisle space is needed. Curvedsections of track carry the cart around corners. Switches can be locatedanywhere in the system to allow transfer from one track to another.
The rack should be designed with removable shelves fordifferent-size plants and should hold from 20-40 flats at one time. Severalracks can be connected together for movement over long runs. Cost of the systemis about $3-5 per linear foot.
Grower-Built Equipment
Growers are very ingenious when it comes to adaptingexisting machines or building new devices to make their job easier. Here are afew examples I have seen over the years.
Flat filler.Attaching two short-belt conveyors together side by side in an X configurationmakes a pot or flat filler. One conveyor is fitted with a hopper at the lowerend that holds about a bale of growing mix and a shoot at the top end to directthe mix to a platform below that supports the container. Excess material fallsinto a containment that drops it onto the second conveyor that carries it backto the hopper. Each conveyor has a separate motor. The speed of the conveyorscan be controlled by the size of the pulleys used.
Watering Tunnel.This can be made using two or three fan-type nozzles attached to a piece of PVCor metal pipe and suspended over a chain or roller conveyor. Water is suppliedto a solenoid valve that controls the water. A lever-type microswitch activatesa 24-volt solenoid valve that turns the water on whenever a flat or pot isconveyed under the nozzles. A transformer converts 120-volt electricity to 24volts to reduce the potential for shock. The excess water can be collected witha pan and piped to a drain, or the unit can be placed directly over the drainin the floor.
Plant carriers. Asimple pot carrier can be made by welding lightweight, 3/4-inch aluminumÁ or steel square tubing perpendicular to a piece of 3/4- x 3/4-inchangle iron and spaced just far enough apart to catch the rim of the pots. Thelength of the tubing is slightly less than a multiple of the diameter of thenumber of pots carried in each slot. A piece of 1-inch conduit bent into a”U” and welded to the angle forms a handle. This concept can beadapted to almost any pot size or shape.
Tractor carry. Thisbox, welded from angle iron and sheet steel, can be designed to fit anytractor. It is attached to the 3-point hitch on the tractor so it can belowered to load materials such as flats, bales or boxes and then raised fortravel.
Plastic roll support.Generally, the easiest way to apply plastic to a hoophouse is to support theroll above the peak of the greenhouse at one end and pull the leading edge thelength of the greenhouse before unfolding it over the frame. A frame,fabricated from steel angle or channel can be attached to a bucket loader. Itshould be wide enough to fit the length of the poly roll. The roll is supportedby wood- or metal-bearing blocks and a steel pipe shaft.
The smaller grower with limited resources has many opportunities to reduce labor input without purchasing expensive equipment. A good understanding of the basic principles that affect labor usage and the adaptation of low-cost purchased or home-built equipment will make operations more efficient.
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