SPECIFICATIONS FOR SEEDING IMPRINTERS

Six categories of imprinting rollers result from various combinations of 2 angle sizes (6"x 6" & 8" x 8"), 2 angle shapes (straight and bowlegged) and two cylindrical core diameters (20" & 24"). Category specifications are given in the table below. Angular teeth are welded radially around the core to form 6 or 8 pointed star rings. Tooth length is 10 inches and the spacing between rings is about 2 inches. Thus, there is one star ring per foot of imprinting roller length. Points on adjacent star rings are staggered to suppress gulley formation. The radial basal spacing of imprinting teeth is also about 2 inches. This 2-inch gap around the base of each tooth improves penetration into the soil while providing a dam between adjacent imprints for safe storage of collected rain or irrigation water until it infiltrates. All six categories of imprinting rollers make imprints or microwatersheds about one-foot square in size and shape. These small isolated watersheds provide excellent control of infiltration and the microclimate, thereby greatly accelerating revegetation processes.

IMPRINTING ROLLER DIMENSIONS IN INCHES

Table 1.  Imprinter Roller Dimensions In Inches

Roller	Cylindrical Core		Angular Teeth Legs		Teeth per
Category	D	C	Length(L)	Width(W)	Star
I	20	62.8	6.0	8.50	6.0
II	20	62.8	6.0	6.00	8.0
III	20	62.8	8.0	8.00	6.0
IV	24	75.4	6.0	8.50	8.0
V	24	75.4	8.0	11.3	6.0
VI	24	75.4	8.0	8.00	8.0

D = Diameter & C = Circumference

 

SEEDER SPECIFICATIONS

 

>The seeder is designed for the selected roller category. Active agitation keeps the seed well mixed while uniformly discharging a controlled amount of seed to the top of the imprinting roller where it is carried forward and imbedded in the surface of the newly formed imprints. Successive rains then move seeds from the upper reaches of the imprinted microwatersheds into the bottom of imprints where moisture conditions favor seed germination and seedling establishment. This process extends the time window of opportunity for successful stand establishment.

> 

>Morphologically diverse mixtures of seeds can be uniformly discharged through time by mixing the seeds with wheat bran--an inexpensive by-product of white flour milling. Flaky wheat bran prevents the fluffy, low density seeds from migrating upward and the smooth, high density seeds from moving downward to ensure a vertically uniform seed mix.

 

Seedbox Shape: Semicircular bottom with vertical sides

Seedbox Height: Same as roller core diameter (D)

Seedbox Width: Same as seedbox height or D

Seedbox Length: Same as roller core length

Seed Agitator: Rotating vane type with 4 flexible blades

Agitator Drive: Rubber tire in frictional contact with imprinting tooth ring

Seed Discharge: Via one-inch circular holes (one per tooth ring) with discharge rate controlled by a sliding gate with holes matching those in the bottom of the seedbox.

 

 

 

IMPRINTER TOW FRAME

 

The front and rear of the tow frame are square tool bars which permit the use of commercial tool clamps for easy attachment of hitches and accessories. Typically the drawbar tongue is removed for trailer hauling to reduce the width of the load. Since the front and rear of the tow frame are identical, hitches can be attached to either side to reverse the direction of roller rotation. This feature nearly doubles the life of imprinting teeth, the tips of which concave sharpen on their leading edges.

Frame Shape and Size: Rectangular to fit rollers 3,4,5,6,7,8,9 & 10 feet in length

Frame Front & Rear: Square tool bar (2 ¼-inch side)

Frame Ends: Clamped to tool bars with center bearing bracket

Roller Axle: Full-length, cold-rolled steel, 2 ½-inch diameter

Axle Bearings: Pillow block type with cast steel housing and double

tapered roller bearings for 2 ½-inch axle

Tool Bar Attachments:

•  Drawbar tongue for field operation

•  Trailer loading and unloading wheels

•  Three-point hitch ( optional )

•  Ripping shanks ( optional )

Imprinter tow frame with imprinting roller and loading/unloading wheels attached

D. FIGURES

Figure 1 Category I, 6-foot imprinting roller used in a demonstration imprinting seeder.

Figure 2 Foreground: Imprints made by the demonstration imprinting seeder
at a sand and gravel mine near Moorpark, CA .

Figure 3 Category II, 7-foot imprinting roller designed for revegetating steep slopes.
The curvilinear triangular teeth are a new development.

Figure 4 Category IV, 8-foot imprinting roller designed for revegetation of degraded
land areas in the deserts of southern California and elsewhere. The imprinter with
this roller has attachments for ripping, mycorrhizae inoculating, and seeding while imprinting.

Figure 5 Imprints made by the roller pictured in figure 4 at a sand and gravel mine near Pearblossom , CA .

Figure 6 Category IV, 10-foot imprinting roller which is the heart of an imprinting seeder
being used to revegetate the Fresh Kills Landfill on Staten Island , New York City.

Figure 7 Four seedbox shells (24 inches in diameter and 24 inches high) to be
used with the category IV, V and VI imprinting rollers which are 8 feet long.

Figure 8 Landfill seeding imprinter with water ballast tanks and transport wheels.
Note the rubber tire drive for the seed agitator which is centrally located and the Fresh Kills Landfill forming the horizon.

 

 

 

IMPRINTING FORCE

Land imprinting obeys the balance of force equation:

Downward Acting Force = Upward Acting Force

or

Imprinting Force or Pressure = Soil Load Bearing Capacity

thus, an imprinting roller will penetrate or settle into the soil to the depth where the opposing forces are equal or balanced. For a full-tooth imprint, these forces balance when the teeth penetrate the soil halfway, because of the embossing effect. When soil load bearing capacity is too high or the soil is too hard for halfway penetration of the imprinting teeth, additional weight can be loaded onto the imprinter or the soil can be softened by ripping or wetting. Usually the best alternative is to add more weight up to a static imprinting pressure of about 30 psi.

Imprinters are designed to have an adjustable range of static imprinting pressures of 15 to 30 psi. For the 8-foot imprinter with straight angles, the base 2-ton weight gives an imprinting pressure of about 15 psi. Loading the imprinter with an additional 2 tons raises the imprinting pressure to about 30 psi. Thus, as a rule of thumb, the static imprinting force per foot of roller length should range from 500 pounds when the imprinter is unloaded to 1000 pounds with a full load. Imprinter loading is accomplished by filling the imprinting roller core with water and by mounting water tanks or soil boxes on the imprinter frame. Tanks or boxes are mounted on both sides of the seedbox such that the weight is balanced over the axle of the imprinting roller ( Figure 8 ). Tanks are the same size as the imprinting roller core, whereas soil boxes are about the size of the seedbox. The outer side of soil boxes should be removable to expedite emptying of the well settled soil. The imprinting tow frame, pictured in Section C, can be loaded using the tractor's hydraulic system and 3- or 4-point hitches or by soil boxes attached to the tool bar frame.

Tillage before imprinting kills existing vegetation, covers plant litter, breaks down soil structure, and encourages weed growth. Thus, tillage should be avoided as an alternative to adding weight to the imprinter frame. However, if tillage is required because of deep soil compaction, ripping is less destructive than disking. Also, mycorrhizal inoculum can be injected several inches deep behind the ripping shanks.  

Another alternative to ripping hard soils, is to imprint them twice. For instance, if the first imprinting is only one-half of the full depth, the second one will be markedly deeper because imprinting teeth tend to get in gear with the first imprints and then bite deeper into the soil.

The static pressures of 15 and 30 psi are based on the soil contract area resulting from the halfway penetration of 6 teeth for the 8-foot imprinter. The general formula for the number of teeth in contact with the soil is 1.5 times the number of in-line teeth or 0.75 times the length of the imprinting roller in feet. The quantitative soil mechanics of land imprinting is extraordinarily complex and poorly understood. Thus, the analysis presented here is only a greatly simplified first approximation.

Finally, it should be noted that the actual or dynamic imprinting pressures are much greater than the static pressures. Soils with a hardness of 100 psi, as measured with a cone penetrometer, can be imprinted by an imprinter producing a static pressure of 30 psi. Thus the momentum of the revolving imprinting roller apparently increases imprinting force by more than 3 times. Just as stepping lightly on soft soil leaves no footprints, stamping, running and jumping does. Another explanation is that the imprinted soil weakens the adjacent unimprinted soil, thereby lowering the imprinting force required as the imprinter rolls along.

Under field conditions, soils usually vary greatly in hardness from point to point with some areas requiring ripping and some not. A tractor equipped with a ripping tool bar and a drawbar for towing the imprinter allows the operator to selectively rip only the hard spots while imprinting the whole area.

SEEDING IMPRINTERS: SUMMARY OF STANDARD SPECIFICATIONS*

1. Imprint geometric shape: V-shaped trough.

2 . Imprint top shape: Rectangular almost square.

3. Imprint top area: About one square foot.

4. Imprint length: 10 inches.

5. Imprint top width: 6 to 12 inches.

6. Imprint end spacing: 2 to 3 inches.

7. Imprint side top spacing: 2 to 3 inches.

8. Imprint depth: 4 to 7 inches.

9. Imprint pattern: staggered (Fig. 5, Dixon & Carr 2000).

10. Imprinter teeth: Ten-inch lengths square cut from 6"x6" or 8"x8" steel angle.

11. Imprinting roller length: 3 feet up to a 10-foot maximum in one-foot increments.

12. Roller core diameter: 20-inch minimum.

13. Imprinting pressure: Adjustable from 15 to 30 pounds per square inch (psi).

14. Imprinter weight: 500 pounds minimum per foot of imprinting roller length.

15. Imprinter ballast: 500 pounds minimum per foot of imprinting roller length.

16. Seeder Design: Seed agitating and discharge mechanism uniformly distributes trashy or fluffy seed mixes of native species just in front of the imprinting roller at the prescribed rate per acre.

Notes

a. See Table 1(Dixon & Carr, 2000) for the six categories of imprinting rollers which satisfy the first twelve specifications, listed above.

b. Land imprinter should be loaded enough to produce full-tooth imprints. Deeply compacted soils should be ripped before imprinting.

c. Imprinter seed sometime during the fall months preferably following the first good rain but before the ground freezes.

d. Native seed mixes for ecological restoration should include early, mid and late successional species with at least one-fourth by weight being the seeds of early seral or pioneer species. Also include a cool season annual grass to provide quick cover for erosion control.

e. Conversion factors: 1 inch = 2.54 cm, 1 foot = 30 cm, 1 psi = 6.90 Kpa, 1 pound = 453 gm.

* Specifications were published in the year 2000 and updated in 2003. Details may be found in the publication: Dixon , R.M., and A. B. Carr 2000. Land Imprinting Specifications for Ecological Restoration and Sustainable Agriculture. Proc. Conference 31, International Erosion

Control Association. February 21-25, Palm Springs, CA p. 157-169.