7.10 PERMANENT EROSION CONTROL

The normal periods for permanent urban and rural seeding are from March 1 to May 31 and from August 10 to September 30. Native grass and wildflower seeding dates are between April 1 through May 31 and November 1 until ground conditions are unsuitable for seeding due to moisture or frost. Wetland seeding dates are between April 1 and June 30. Spring overseeding is typically performed after February 1 and before April 1. Refer to Construction Manual Section 7.16 for more information on overseeding.

These dates may be modified by the Construction and Materials Bureau or the Design Bureau (Roadside Development Section). Changes in the dates will be based on temperature and moisture conditions and possibly specific project considerations.

Seeding date extension notices will be posted on the Construction and Materials Bureau website:

https://iowadot.gov/construction_materials/Earthwork-and-erosion-control

Any other extensions or dormant seeding are at the discretion of the Engineer on a project-by-project basis.

7.11 PREPARATION OF SEEDBED

Before seeding operations commence, care should be taken to properly prepare the area to be seeded. Areas around culvert headwalls and wingwalls, shoulders, flumes, signposts, and other structures require special attention. The seedbed shall be worked to a depth of at least 3 inches deep with field machinery and at least 2 inches deep in locations prepared by hand. The specifications require certain areas such as raised medians, islands, and rest areas to be prepared with a Rototiller.

All debris, including stones 3 inches in diameter and larger, logs, stumps, wire, and other objectionable material shall be picked up and disposed of off the project.

If there is enough vegetative growth (i.e., weeds or temporary seeding) to sufficiently interfere with proper seedbed preparation, the contractor is to mow before seeding at no additional cost to the Contracting Authority, unless indicated otherwise in the plans. Or in the case of installing permanent native grass seed using a drill with a no till attachment, no seedbed preparation is required. However, mowing of temporary seeding may be required.

7.12 PREPARATION OF SEED MIXTURE

Seed

Permanent rural, permanent urban, urban stabilizing, Native Grass, Wetland Grass, and Wildflower seeding mixtures are required to be mixed off-site by a seed conditioner approved by ICIA or other state’s Crop Improvement Association. For more information on the seed conditioner program, refer to ICIA website: http://www.iowacrop.org/Seed_Directory.htm. Additional links are provided at: https://iowadot.gov/construction_materials/Earthwork-and-erosion-control

Mechanically printed seed tags and the seed mixture reports should be checked to verify that it complies with minimum purity and germination requirements, current test data, and variety. The date of the germination test should be checked also. The specifications, based on the Iowa Department of Agriculture regulations, require that the test date be within a 9-month period exclusive of the calendar month in which the test was completed. For example, seed tested 8/5/12 shall be applied by 5/31/13. If seed is to be applied after 5/31/13, then seed requires a new test. Refer to Materials IM 469.02 for more information on acceptance of seed.

If the test information indicates noncompliance for purity and germination requirements, the seed may be used on a pure live seed (PLS) basis providing:

n Seed meeting the requirements cannot be obtained, and

n The seed meets the approval of the project engineer.

For each seed variety or mix, remove and retain at least one seed tag per day of seeding that was inspected. If the inspector is not onsite, then the contractor should collect and provide tags/tickets for the seed, fertilizer, and mulch applied so the inspector can verify quantities placed.

When seed is used on a pure live seed basis (PLS), the quantity required must be calculated from test results. If the project requires 10 pounds of Switchgrass PLS per acre, and the tag rated the furnished seed at 98% purity and 95% germination, the pure live seed is computed as follows:

Purity = 98% = 0.98

Germination = 95% = 0.95

PLS (Pure Live Seed) = Purity X Germination

= 0.98 X 0.95

= 0.93 = 93% PLS

To calculate the number of pounds of seed required to provide

10 pounds PLS:

10 pounds / 0.93 = 10.75 pounds of seed per acre

Sticking Agent

Seed to be inoculated shall be treated with a sticking agent prior to the application of the inoculant. A sticking agent is not required with liquid inoculant.

Inoculant

An inoculant is required for legume seed. An inoculant is a culture of bacteria specifically formulated to enhance the growth of the seed. The inoculant shall be a type recommended by the manufacturer and applied at the rate according to our specifications.

Red clover is an example of a legume that was previously specified in stabilizing crop seeding.

Seed Mixtures

Each bag shall have seed tags with information such as seed species, lot numbers, seed test date and seeding rate percentages (which is oftentimes shown as purity for the mixture).

For example:

Oat 47.5%

Grain Rye 46.5%

Canada wildrye 4.8%

Other 1.2%

A 50 pound bag of mixed seed would contain 23.75 pounds of Oat, 23.25 pounds of Grain rye, and 2.4 pounds of Canada wildrye.

The seed mixture reports should also include the project number, seed test information, and lot numbers.

The Department is not obligated to purchase remaining amounts of premixed seed as “unincorporated material.”

7.13 RURAL SEEDING

The following suggested sequence of operations for temporary rural seeding (also called rural stabilizing crop seeding) is as follows:

1. Prepare seedbed (except for stockpiles where areas are not accessible to field equipment)

2. Apply fertilizer and roll prior to seeding

3. Apply seed with gravity, cyclone, hydraulic, native grass seed drill with split rate application (no less than two passes).

4. Cover seeding and fertilizing with a light disking or other tillage equipment such as a rigid harrow, spring tooth harrow, or field cultivator.

5. Follow tillage with a cultipacker.

6. Apply mulch.

7. Tuck mulch with mulch anchoring equipment

The following suggested sequence of operations for permanent rural seeding when seedbed preparation is required by the specifications is as follows:

1. Prepare seedbed

2. Disk in fertilizer and roll the area prior to application of permanent seed.

3. Apply seed using drop seeder (with pulverizer rollers and packer wheels) with split rate application (no less than two passes).

4. Apply mulch.

5. Tuck mulch with mulch anchoring equipment

The following suggested sequence of operations for permanent rural seeding when seedbed preparation is not required by the specifications is as follows:

1. Seedbed preparation is not required.

2. Apply fertilizer (but no disking).

3. Apply seed with slit seeder or with native grass seed drill with a no till attachment with split rate application (no less than two passes).

4. Roll after application of seed.

7.14 HYDRO‑SEEDING (HYDRAULIC SEEDING)

The suggested sequence of operations using a hydro‑seeder is:

1. Prepare seedbed

2. Apply fertilizer, seed, inoculant, and water with hydro‑seeder

3. Roll with cultipacker

4. Place mulch where specified

5. Tuck mulch with mulch anchoring equipment (step not required if hydro-mulch is used)

The following items should be noted when inspecting hydro‑seeding:

A fanning motion or horizontal motion of the seeding nozzle insures uniform application of the seed. Do not use an "up and down" motion; it results in seed application too heavy near the seeder and too thin at the far reach of the spray.

The seeder tank must be cleaned when changing seed mixtures.

The agitator in the seeder tank must be in operation for a period of time prior to starting the seeding to insure mixing of the material in the tank. After mixing and during application of material, a continuous operation with a constant pressure must be maintained during the seeding.

The contractor should apply the mixture of water, seed, and fertilizer with the wind, if possible. The contractor should try to prevent mist from blowing across the roadway if open to traffic.

The seed may be in the fertilizer solution for no more than one hour.

If hydraulic mulching is used with hydraulic seeding, they must be performed as separate operations. To keep seed from floating to the top in the equipment during hydraulic seeding, a bag of hydraulic mulch may be added to the seed. However, this bag will not be included as part of the required mulching rate (minimum 3,000 pounds per acre).

7.15 URBAN SEEDING

The suggested sequence for temporary seeding in urban areas is:

1. Seedbed prep with a rotary tiller

2. Apply fertilizer and roll prior to seeding. For rolling, use either open grid type equipment or cultipacker type equipment modified by covering with expanded metal mesh.

3. Apply seed with gravity, cyclone, hydraulic, native grass seed drill with split rate application (no less than two passes).

4. Roll after application of seed.

5. Apply mulch (typically hydraulic mulch is used in urban situations).

The suggested sequence for permanent seeding in urban areas is:

· In areas with urban crop stabilizing 50% or more,

5. Seedbed preparation is not required.

6. Apply fertilizer (but no disking).

7. Apply seed with slit seeder with split rate application (no less than two passes).

8. Roll after application of seed.

· Other areas:

1. Prepare seedbed with a rotary tiller

2. Apply fertilizer and roll prior to seeding. For rolling, use either open grid type equipment or cultipacker type equipment modified by covering with expanded metal mesh.

3. Apply seed with gravity, cyclone, hydraulic, native grass seed drill with split rate application (no less than two passes).

4. Roll after application of seed.

5. Apply mulch (typically hydraulic mulch is used in urban situations).

7.16 NATIVE GRASS SEEDING

The suggested sequence for native grass seeding is:

1. Seedbed preparation and cultipacking will not be required. However, mowing may be required.

2. No fertilizer.

3. Apply seed with native grass seed drill with a no till attachment. Perform two passes with drill, with second pass being offset from first pass.

4. Place and tuck mulch – unless area contains rural stabilizing crop residue.

7.17 OVERSEEDING AND FERTILIZING

Spring overseeding or "frost overseeding" is the application of permanent seed without preparing a seedbed. Spring overseeding is performed normally in February or March, but may be modified depending on the weather conditions.

The following guidelines should be used to determine when spring overseeding is allowed:

n Ground is relatively free of packed snow and ice.

n Light snow cover of not more than 1 inch.

n The project may be free of snow and ice with the exception of a few ditches or slope areas. It would be permissible to allow the overseeding with the stipulation that the contractor would reapply the seed on those designated ditches or slopes as soon as the snow and ice have melted.

The application of seed when the ground is loose and friable from frost action provides a favorable condition for the earliest possible seed establishment. The application of seed prior to this ideal condition is more favored than after the ground is free of frost and dry. Seed applied when the ground is frozen is not generally detrimental. The loss of seed due to runoff, in the event of heavy spring rains or snow melt, should be minor.

7.18 AERIAL SEEDING

Aerial seeding is only allowed when specified in the contract documents. The distribution of seed on the ground should be checked during the aerial seeding operation. If a significant quantity of seed falls onto the roadway shoulders or off of the right‑of‑way, the seeding operation should be halted, and corrective action taken. For aerial application, the wind velocity should be less than 10 mph.

As a guide, the following is a part of the Beaufort Scale for wind velocity:

Type	Observations	Speed (mph)
Calm	Calm. Smoke rises vertically.	(0‑1)
Light air	Direction of wind shown by smoke drift but not by wind vanes.	(1‑3)
Light breeze	Wind felt on face. Leaves rustle. Ordinary vane moved by wind.	(4‑7)
Gentle breeze	Leaves and small twigs in constant motion. Wind extends light flags.	(8‑12)
Moderate breeze	Raises dust and loose paper. Small branches are moved.	(13‑18)
Fresh breeze	Small trees with leaves begin to sway. Crested wavelets form on inland waters.	(18‑24)

A subcontract request form is not required for the aerial applicator (airplane or helicopter), which is usually owner‑operated.

Guidelines to allow/disallow use of local roads for takeoff and landing of planes which seed areas on primary projects are:

· Primary roads or local roads designated as detours shall not be used for takeoff/landing

· Takeoff/landing should be with written permission of the county engineer or local agency and with traffic control and signing as required by the owner of the road

· The owner of the road may, at their discretion, ask the applicator for:

-- A “waive and hold harmless” agreement to reduce liability

-- Proof of insurance

· Federal Aviation Regulations (FAR) are listed in Title 14 of the U.S. Code of Federal Regulations. They are available to view at Web address: https://www.faa.gov/regulations_policies/faa_regulations/

Applicable regulations are “FAR Part 91 – General Operating and Flight Rules” and “FAR Part 137 – Agricultural Aircraft Operations”.