Each kind of seed has its own safe moisture content for sealed storage in the Temperate Zone. Tomato, pepper, cabbage, and cauliflower seed should not contain more than 5 percent of moisture for safe storage in hermetically sealed metal cans held at moderate temperatures. Other maximum seed moisture levels for safe storage in such cans are: Celery and lettuce, 5.5 percent; cucumbers, watermelons, cantaloups, onions, and eggplants, 6 percent; parsley, 6.5 percent; carrots, peas, 7 percent; beets, 7.5 percent; and spinach, sweet corn, beans, lawn grasses, 8 percent.

PACKAGES are filled in many ways. The equipment may be a simple spoon or seed scoop; the gravity flow from a manually controlled bin; or a highspeed, completely automatic small Jacket, metal can, or plastic bag filler. Most filling equipment has a measuring device or is controlled manually or automatically on a signal from a weighing device.

Practically all seeds, except those in small packets, are sold on a weight or volume basis. Even those seeds that appear to be sold on a volume basis are associated with weight for example, a bushel of corn is 56 pounds; a bushel of wrinkled peas is 56 pounds; a bushel of smooth peas is 60 pounds.

To meet these requirements, it is necessary to put into the individual packages a selected amount of seed by weight or by volume, the latter being related to a selected weight. Weighing devices range from an ordinary beam scale to an elaborate scale that activates a pneumatic or an electrical device to shut off the flow of seed when a weight or volume is reached.

Rigid containers always have the same volume, but the seed placed in them may vary in weight for the same volume. Oats, for example, may weigh 34 pounds to a bushel one year and 28 pounds the next. A similar variation may occur in different areas the same year. In order to get the proper weight of seed into a rigid container, it may have to be vibrated while it is being filled, particularly if the seeds are light and fluffy or do not flow readily. The vibrator may be attached to the platform that supports the container while it is being filled or the side of the container may be placed in contact with a vibrator.

Some seeds are sold on the basis of number, either actual or adjusted for percentage of pure live seed (the percentage of pure seed times the germination percentage). It may well be that in time most seed will be sold on a pure, live-seed basis. Some companies package hybrid corn seed in acre units. Each package contains the correct amount of seed for planting a specified number of acres.

Except in small operations, seeds to be packaged are delivered to hopper bins above the filling machines. Seeds may come to the hopper from bulk storage bins by gravity flow through pipes, by airlift, belt conveyors, storage boxes or in bags handled by bag elevators, forklifts, or on a man's shoulder.

All handling of the seeds must be done with care, as there may be some effect on the physical quality through impact or undue pressure.

Heavy seeds, especially those of beans, peas, corn, and soybeans, can be fractured if they strike or are struck by a hard object or firm surface. The breaks may not be readily visible in the dry seeds. The severity of injury is related to the moisture content and the force of impact. Seeds that contain too much or too little moisture are damaged easily. Seeds may be damaged when they are forced through a restricted opening.

Injuries may also be caused by rough handling of packages and planting with equipment that squeezes the seeds as they are fed into the planting spout. The damage may kill the embryo or cause a weak or abnormal seedling to be produced for example, beans without complete cotyledons and baldhead bean seedlings, which lack a terminal growing point. Mechanical damage also shortens the storage life of seeds, even when they are held under the most favorable conditions of storage.

The types and sizes of packages used for wholesale distribution often are quite different from the ones used for retail sales. Processors usually package seeds in burlap, osnaburg, or seamless and multiwall paper bags that hold 50 or 100 pounds or one-half to 3 bushels.

A number of companies use moisture-barrier packages (such as elastic multiwall paper bags with an asphalt or a polyethylene or aluminum foil barrier ply in the multiwall), burlap or cotton bags with polyethylene liners and burlap/asphalt/paper bags for seed of cereal grains, soybeans, hybrid sorghums, hybrid corn, cotton, peas, beans, sweet corn, coniferous and broad-leaved trees, and various other kinds. Hybrid corn seed is also packaged in 7- or 10-mil polyethylene bags.

A valve-type polyethylene bag, developed in 1959, prevents loss of material while filling and is sealed more easily than the conventional bag. Fumigants and inert gases can be easily introduced into the filled bags.

Some alfalfa seed is packaged in large cardboard cartons. Flower seeds are sometimes packaged in cans.

Large, nonrigid containers (burlap, cotton, lined bags, multiwall and 7- and 10-mil polyethylene bags) are usually positioned manually. They are held in place by hooks or clamps or by hand during filling.

Hand tying of the open ends of cotton and fiber bags has been largely replaced by sewing, done mostly with sewing machines adapted for this purpose. Multiwall paper and laminated bags are closed by sewing or sewing and taping, and polyethylene bags are closed by heat sealing.

Heat sealing of polyethylene and other thermoplastic materials is accomplished by applying heat (200 -400 ) to the film while the point of closure is under pressure. Each kind and thickness of material has specific requirements as to temperature, time, and pressure for proper sealing.

Heat sealers include small hand irons or rollers, hand- or foot-operated jaws or clamps, and elaborate, automatic machines for forming, filling, and sealing bags and pouches. Some sealers use thermostatically controlled bars, bands, or rollers. Others use a brief, high-intensity thermal impulse. Most sealers are readily adjustable for use with many kinds of materials.

A wide variety of materials and package sizes are utilized in preparing seed for retail sales. Most field seeds are sold at retail in the original wholesale packages, but seeds of vegetables, flowers, and lawn grasses are packaged for various types of retail customers. Multiwall paper, cloth, and plastic bags; cardboard boxes and drums; and metal cans of 1 to 10 pounds' capacity are used for grass and vegetable seeds for truck farmers.

Small paper, foil, and plastic packets and cardboard boxes that contain a few seeds, a fraction of an ounce, or several ounces are used for mail-order and store sales of vegetable and flower seeds. Tobacco seeds usually are packaged in paper packets that hold one-half ounce and 1 ounce.

The medium and small flexible and semi-rigid containers used for retail packages may be preformed or formed into bags or packets from sheets or rolls. Preformed containers can be opened with a jet of air and automatically or manually positioned for filling. The high-speed automatic fillers pick up and position the individual packets in ferris wheel or merry-go-round fashion. A specified amount of seed is injected into each opened packet at the rate of one per second. When bags or packets are formed from sheets or rolls, they are formed, filled, and sealed in one continuous operation on a single- or a many-unit machine.

Metal cans, glass jars, and fiber drums come from the manufacturer ready for filling. Usually they are delivered to the filler by conveyors which automatically position each unit.

Most fabric and some paper containers are sealed by sewing or sewing and taping. Most paper and cardboard containers are sealed with cold or hot glue. If the number of packages processed at a time is fairly large, sealing is done automatically with hot glue.

The various types of plastic packages are heat sealed.

Rigid containers, such as fiber drums, may have slip-on caps or lids that clamp into position and are applied manually. Metal and glass containers usually have the lid end sealed with special closing machines.

Can sealers are manually operated, semiautomatic, and fully automatic. Placing seed in rolls of tape may be considered a form of packaging. The American Seed Tape Co. in the 1920's developed machines for forming the tape, placing the seed, and making the roll. This form of packaging did not become an accepted sales instrument at that time, but was revived later.

Seed packages must be labeled to show the species, variety, percentage of live seed, purity, content of noxious weeds, and seed treatment, if any. The information may be printed on a tag attached to the bag. It may be printed on a label that is glued to the container. It may be printed or stamped directly on the container. Seedsmen usually print their own tags and labels.

Stenciling on bags may be done manually or automatically by rotary printer as the container passes a point on an assembly line. Embossing normally is done by the closing machine.

Special labeling machines can apply glue to the can or label and wrap the label around the can as it rolls through the machine. A special printer may imprint information on the can before the label is applied so that it can be identified even if the label is removed.

The final packaging operation is the assembling of the packages. Large containers may be brought together by belt or roller conveyor or placed by hand on pallets handled by forklift, or by use of hand trucks. Smaller units frequently are placed in larger cartons by hand or automatically with equipment built to assemble a selected number of units and place them in cartons.

The seeds are then ready for transportation and distribution to their eventual destination in the good earth, where their germination will demonstrate the protective value of modern packaging.

Louis N. BASS is a plant physiologist in the Agricultural Research Service, National Seed Storage Laboratory, Fort Collins, Colo. Formerly he was assistant professor of botany and plant pathology in Iowa State University.

TE MAY CHING is an assistant agronomist, Farm Crops Department, Oregon Agricultural Experiment Station, Corvallis.

FLOYD L. WINTER is vice president and director of breeding and research, Asgrow Seed Co., New Haven, Conn.