Instructions for Building Poor Boy Tobacco Seeders

 

Robert D. Miller, Richard A. Hensley, and Uel D. Wilhoit


 

Research Report 94-04

February 1994

 

 

 

Department of Plant and Soil Science

Agricultural Experiment Station

University of Tennessee

Knoxville, Tennessee

 


Introduction | Construction of the Frame | Construction of the Plexiglass Plates | Construction of a Poor-Boy Dibble Board
Using the Poor-Boy Seeder | Seeder Materials List | Estimated Seeder Materials Cost | Dibble Board Materials List


Introduction

The "Poor Boy" tobacco seeder is a relatively inexpensive tool for dispensing pelletized seed into styrofoam trays used for growing tobacco "float" plants. The seeder consists of a pair of plexiglass plates with holes drilled in them, mounted in a wooden frame that fits over the tray being seeded (Figure 1). The frame is constructed to permit the top plate to slide over the bottom plate, allowing the holes in the two plates to be alternately aligned or offset. The holes are offset to load the seeder, and aligned to discharge the seed into the trays.

The exact dimensions of the Poor-Boy seeder will vary somewhat depending on the brand of tray being used for plant production. Most trays are approximately 13 1/2" wide and 27" long, but they may vary in length or width by as much as 1/2". There is also a significant difference in the cell configuration among tray manufacturers for a given tray size. In order for the seeder to work properly, it should be custom built for a specific tray brand and cell number. The seeder parts included in the Materials List are the correct size for Speedling and Carolina trays. Growers using trays from other manufacturers will need to adjust sizes as necessary.

Construction of the Frame

The inside dimensions of the seeder frame should be 1/4" wider and 4" longer than the dimensions of the styrofoam trays being used for plant production (Figure 2). The added length is to allow an area for storage of excess seed while the seeder is being discharged. The rear end of the frame is hinged to allow the removal of the plexiglass plates for cleaning or replacement. Corner irons are used on the bottom to help reinforce and square the frame, and 1/4" drywall screws are used to secure the ends of the frame to the sides (Figure 3). The plexiglass plates are held securely in place by right-angle vinyl strips that run along each side of the top of the seeder frame and 3/4" x 1/2" wooden support rails that are attached to the inside of the frame (Figure 4). The vinyl strips are obtained by ripping one 3/8" x 1/4" vinyl window header (available at most companies selling vinyl siding for houses) lengthwise to form the two pieces needed for one seeder. The strips are attached to each side of the wooden frame by five 6 x 1/2" pan head sheet metal screws (Figure 2).

The easiest way to get the proper spacing between the vinyl strips and the wooden support rails is to first build the frame and attach the vinyl strips. Turn the frame upside down and lay both plexiglass plates in the frame. Position the wooden side support rails on top of the plexiglass and against the inside walls of the frame. The support rails should fit snugly, but do not push them down against the plexiglass plated. If the fit is too snug, it will be difficult to slide the plates during seeding. The sliding action of the seeder is obtained by attaching a 1/4" thick plywood spacer to the inside front of the frame with two 4 x 3/4" wood screws (Figure 4). The spacer is positioned so that only the bottom plate will butt up against it. The top plate should clear the spacer. This will permit it to slide forward by 1/4" to allow the holes to be offset for seed loading, and backward to discharge the seed into the tray. Mark the position of the side support rails, remove the plates, and attach the rails to the frame sides with four 4 x 3/4" wood screws. Reinsert the plexiglass plates and mark the position of the front, middle, and rear cross support rails (Figure 3 and Figure 5). The cross supports can be attached either by wood screws or wood glue. If they are glued in place, make sure that the rear cross support is not glued to the hinged portion of the end wall (Figure 5). Do not glue the support rails to the bottom plexiglass plate; this would prevent the removal or changing of plates within the seeder.

Construction of the Plexiglass Plates

The two plexiglass plates are shown in Figure 6. The thickness of the top plate should be .060 inch (1/16"). This is critical to ensure that the holes in the plate hold only one seed at a time, as most brands of pelletized seed are 1/16" in diameter. Plexiglass of this thickness is difficult to find. If .060 thick plexiglass is not available, .093 (3/32") may be used. However, this will result in some cells receiving two seed unless the top plate is brushed lightly after loading to remove double seed. A "Bounce" fabric softener sheet can be used to brush off any double seed and prevent static buildup on the plexiglass plates. The bottom plate should be 1/4" in thickness to offer adequate support and prevent the seeder plates from bowing or sagging in the middle.

To ensure that the holes in the top and bottom plates will align properly, both plates should be drilled at the same time. The plates should be perfectly aligned and attached with duct tape to the bottom of the styrofoam tray used for plant production. Using a straight edge, draw lines across the length and width of each row of cells to form "crosshairs" over each cell (Figure 6). Approximately four inches of the plates will stick out over one end of the tray. This area will not have holes and will be used to hold excess seed while individual trays are being seeded.

With the two plexiglass plates still taped to the styrofoam tray, drill 3/32" diameter holes through both plates. The 3/32" size is critical to ensure that one, and only one, seed will fit into each hole. After all of the holes have been drilled, remove the top plate and redrill the holes in the bottom plate using a 5/32" or 11/64" bit. This will allow seed to fall into the trays even if the holes in the top plate are not exactly centered over those in the bottom plate during seed discharge.

After holes in both sets of plates have been drilled, railings need to be attached to the top plate to keep the seed from spilling out during the seeding process (Figure 6). Load both plates into the seeder frame, being careful that the sides of the plates that were facing up during the drilling process are facing up in the frame. Position the side rail and end rail plexiglass pieces in place for gluing. The side rails should line up against the vinyl strips on the top of the seeder frame (Figure 2). Mark the position of the plexiglass rails and remove the plates from the wooden frame. Carefully place the side rails in the correct positions and glue to the top plate using plexiglass glue. Gluing should be done from outside the seeding area to prevent spillage of glue on the surface of the plate. A 3" cover should also be glued to the top of the plexiglass side rails at the end of the plate containing the seed storage area (Figure 7). This lid or cover prevents seed from bouncing out of the seeder during the seed loading process.

The final step in completing the Poor-Boy seeder is installation of a hinged "tailgate" to trap the excess seed in the storage area of the top plate while the seed is being discharged. The tailgate is made by drilling a hole through the plexiglass side rail and into the end of the tailgate piece using a 1/8" drill bit (Figure 7 and Figure 8). Re-drill the holes in the side rails using a slightly larger bit to allow the tailgate to hinge freely. The tailgate is attached with two 6 x 1/2" pan sheet metal screws (Figure 8).

Construction of a Poor-Boy Dibble Board

When direct seeding, it is desirable to get a high rate of germination over a short time span. This is sometimes difficult to achieve if the seed are simply placed on top of the soil mix. The percentage and uniformity of seed germination are greatly improved by "dibbling" (making holes in the soil) the trays before seeding. We have achieved best results by placing the seed into dibble holes that are 1/2" to 3/4" deep. Wooden or cast aluminum dibble boards can be purchased, but they are relatively expensive; prices range from approximately $90 for a wooden board up to $200 for a cast aluminum one.

A relatively inexpensive dibble board can be constructed by using 3/4" plywood and electrical wire nuts (Figure 10). The plywood should be cut 1/8" longer and 1/8" wider than the float trays that will be used. Place the top-plate of the Poor-Boy Seeder on the plywood and mark the location of the holes around the perimeter of the seeder plate on the plywood with a felt-tip marker. The individual dibble holes can then be located with "cross-hairs" by drawing lines across the width and length of the board, using the ink dots as guides. Attach a wire nut to the board at each cross-hair with a 1 3/4" six-penny box nail or a #6 x 1-58" trim head screw. GreenGard brand #95 screw-on ground connectors have a pre-drilled hole in the end, making them the easiest wire nuts to use (Figure 11). The nails or screws can simply be slipped through the holes to allow easy attachment of the connectors to the board. The connectors can be purchased at most building supply stores, with prices ranging from $8-10 for an 100-count box.

Side and end walls made of 3/4" plywood should be added to the dibble board to form a box that can be slipped over the tray being dibbled to ensure that the wire nut is centered over the cells. Handles fastened to the top of the dibble board make it easier to use (Figure 12).

Using the Poor-Boy Seeder

Before seeding, the soil in the trays should be "dibbled" to form holes to accept the seed. The soil must be wet in order for the dibble board to form good holes. If dry soil mix is used, the holes will refill when the dibble board is removed. Trays should be filled with potting mix and floated on the water bed for at least 24 hours before dibbling and seeding. This allows the soil to absorb water, enabling proper dibbling. "Dry cells," which result from air pockets in the soil mix, can be easily detected in the floating trays and refilled before dibbling and seeding.

The seeder is used by loading one or more packages of seed into the seed storage area (Figure 7). Slide the top plate forward until it hits the front wall of the frame; the holes in the two plates should be offset. Open the tailgate and roll the seed across the top plate (Figure 8). Gently roll the seed back and forth across the plate until each hole holds one seed. Open the tailgate and tilt the front of the seeder until all of the excess seed rolls back into the seed storage area. Close the tailgate and set the seeder down over the tray that is to be seeded (Figure 9). Slide the top plate back until it hits the rear wall of the seeder frame. The holes should be aligned at this point, allowing the seed to be discharged into the tray. Slide the top plate forward to close the holes and repeat the procedure until all trays are seeded. The seeder plates should be cleaned periodically with "Static-Guard" spray to eliminate static buildup. If the seeder will not be used for an extended period of time, it should be stored out of direct sunlight in a cool, dry location.

Trade and brand names are used only for the purpose of information and The University of Tennessee Agricultural Extension Service does not guarantee or warrant the standard of the product, nor does it imply approval of the product to the exclusion of others which may be available.

Seeder Materials List

Plexiglass (1) 30 3/4" x 13 1/2" x 1/16" (Top Plate)
  (1) 30 3/4" x 13 1/2" x 1/4" (Bottom Plate)
  (2) 30 3/4" x 1 1/2" x 1/4" (Side Rails)
  (3) 12 1/4" x 1 1/2" x 1/4" (End Rails and Tailgate)
  (1) 12 3/4" x 3" x 1/4" (Seed Storage Cover)
NOTE: Where 1/16" is stated material is actually .060
Wood (1" Dressed Fir or White Pine Lumber)
  (1) 15 1/4" x 4" x 3/4" (Frame Front)
  (2) 15 1/4" x 2" x 31/4" (Hinged Frame Back)
  (2) 31" x 2 1/2" x 3/4" (Frame Sides)
  (2) 30 3/4" x 3/4" x 1/2" (Side Support Rails)
  (4) 12 3/4" x 3/4" x 1/2" (Cross Support Rails)
  (1) 13 3/4" x 2 1/4" x 1/4" (Plywood Spacer)
Vinyl (1) 30 3/4" x 3 3/8" x 1 1/4" Vinyl Window Header (Side Mounts for Top Plate)
Metal (4) 3" x 1/2" Flat Corner Irons (with screws)
  (2) 1" Hinges (with screws)
  (10) 4 x 1" Slotted Flat Head Wood Screws
  (2) 4 x 3/4" Slotted Flat Head Wood Screws
  (4) 1 1/4" Dry Wall Screws
  (12) 6 x 1/2" Pan Head Sheet Metal Screws

Estimated Seeder Materials Cost

Plexiglass $27.50  
Wood 10.00  
Vinyl 3.00  
Corner Irons 1.75  
Hinges 1.00  
Screws 1.50  
Glue 6.00 - 4 oz. can plus applicator
     
Total Cost $50.75 Prices may vary with location

Dibble Board Materials List

Materials   Approximate Cost
Plywood (1) 28" x 15 1/4" x 3/4" $6.00
White Pine (2) 15 1/4" x 2" x 3/4"  4.00
  (2) 26" x 2" x 3/4"  
Screws #6 x 1 5/6" Trim Head Screws  7.00/100
Electrical Ground Connectors    8.50/100