Category:805 Seeding

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805.1 Construction Inspection Guidance for Sec 805

Description (Sec 805.1)

This work shall consist of furnishing and sowing seed as specified in the contract. Areas to be seeded include earth shoulders, medians, and the entire roadway outside of the roadbed limits, excluding sodded areas, surfaced areas, solid rock, and rock fill slopes consisting primarily of broken rock. The plans specify the seeding mixture, rate of application, and the areas to be seeded in acres. The seeding item includes the cost for fertilizing, liming and mulch materials and their applications.

Material (Sec 805.2)

Seeds shall be grown and processed in the United States or Canada and must comply with requirements of Missouri State Laws. These laws require that each container of agricultural seeds bear a plainly written or printed label, or tag, giving certain information which includes lot number, percent pure seed, percent germination, percent hard seed, etc.

The contractor shall provide a certification with the lot number, percent pure seed, percent germination, percent hard seed, etc prior to applying seed on the project. Certification should carry a statement to the following effect, "This seed is certified to meet all requirements of the Missouri Standard Specifications for Highway Construction." If the seed for the project is mixed prior to arriving on the project, the contractor shall certify the seed mix proportions comply with contract requirements.

In addition to requirements of Missouri Seed Law, the specifications list minimum percentages of purity and germination, which govern unless otherwise permitted by the engineer. Intent of this specification is that seed will not be furnished with less than the percent purity and/ or germination required. However, requests may be received for permission to apply increased quantities of seed deficient in purity and/or germination to compensate for deficiency. In such cases, the resident engineer should consult with the Roadside Management Supervisor, Maintenance, (573) 751-8647, for approval and revised application rate. This procedure will not normally be allowed as it is intended that the contractor furnish seed of specified quality. If approval is granted, the revised rate will not give credit for any excess purity and/or germination that may exist. Seed may be accepted on the basis of label if the data conforms to contract requirements and registered seed technologists or the seed company, provides proper certification verifying in detail the analysis that appears on the label.

Under no condition is approval to be given to reduce specified amounts of seed per acre even if certification and test results indicate purity and/or germination greater than minimums specified.

The inspection is reported on Form T-634, indicating acceptance of the seed. The inspection report will show project designation, identification numbers, lot numbers, kind of seed, quantity, etc.

Stored seed should be protected from moisture, heat, and rodents.

Construction Requirements (Sec 805.3)

The seedbed shall be prepared in accordance with Sec 801. The seeding operation follows after fertilizer has been worked into the soil. Before seed application, the seedbed should be inspected to determine that soil conditions conform to intent of the specifications. Seed should not be applied to eroded, dry, crusted, or frozen soil. Soil with high silt or clay content may crust over following a light shower and deter proper seed application. Soil should be firm, but uncompacted, with a relatively fine texture. Ground preparation when soil is so wet that it clings to equipment is not only impractical but unsatisfactory because soil is not being broken down into fine particles. Preparation when soil is frozen is undesirable for the same reason.


This is a performance-based specification; therefore, it is the contractor's responsibility to furnish materials in quantities according to areas and rates specified. The seeding is to be applied at no less than the rates specified in the contract. The inspector's count of number and weight of bags of seed used is part of his record for approving partial payment for areas completed. The inspector must document when an area is seeded as acceptance is made within 60 days of seeding.

It is usually necessary to mix seed on the project in proportions to provide the proper amount of each seed per acre. The inspector should carefully observe mixing operations to be sure a thorough blend is obtained.

Various methods of sowing are available to the contractor. Each has their advantages and disadvantages. The inspector should note the method used.

Dry Seeding

Broadcast distribution of dry seed is effected by winds. Drills may be used without regard to wind. Normally, a drill operating in one direction produces satisfactory distribution of seeds. Drills have a tendency to place seed too deep. Mechanical seeders should produce satisfactory coverage when operated in one direction only. When seeding is by hand or by mechanical hand seeder, in order to obtain desirable seed distribution, it should be done in two directions, at right angles to each other. Raking, or other approved method, covers the seed to a desirable depth. Care should be taken to preserve proper seed distribution. Seed may also be sufficiently covered by dragging brush, chain, or timber over the seeded area if soil is loose and easily pulverized at the surface, particularly if fine seeds have been sown. Hydraulic Seeding

Hydraulic application is done by what is frequently called the "slurry method". On slopes steeper than 2 to 1 fertilizer and seed may be mixed with water and sprayed on the area in one application. On other slopes seed and fertilizer are applied separately. No seed should be applied which has been mixed with water for more than 4 hours as germination may be effected.

Application Rate

Minimum application rates are required by the contract. Rate of seeding should be checked as soon as possible after beginning operations, and frequently thereafter, by comparing areas seeded with the measured quantity of seed used. Area dimensions, type of seed, and quantities applied should be recorded in the bound notebook in a manner similar to that used for fertilizing and liming.

Reference should be made to Section 802, Mulching, for the effects of inadequate or over application of mulch to the seedbed.

Acceptance (Sec 805.4)

The specification is performance-based. A minimum plant density of 20 plants per square foot is required within 60 days of sowing or by May 1 if sowed between September 1 and March 1. The plants must be of the species included in the project’s seed mix. It may be necessary to ask for assistance from Roadside Development staff in the Maintenance Division, if there is a question regarding plant species present.

In order to obtain the permanent vegetation desired, job seed mixtures are tailored for the region. Initial plant growth typically will be from the annual seeds included in the mix. Competition from annual plants affects the success of permanent plant growth. For this reason, the contractor cannot be allowed to increase the percentage of the annual seeds to the mix.

It is suggested a ring 42.5 inches in circumference be used to check plant density. Visual acceptance may be made after confidence of plant density is achieved after numerous counts are made. Locations, plant density and plant species observed are to be recorded. Documentation of acceptance and rejection must be recorded.

Corrective Action (Sec 805.5)

If an area has not been accepted for seeding and erosion exists due to the lack of ground cover, the contractor will be responsible for the repair. Cost to repair erosion from sheet and rill flow is the contractor’s responsibility. In the event gulley erosion results from linear flow drainage from outside the construction area, the resident engineer should authorize payment to the contractor to make the necessary repairs.

Method of Measurement (Sec 805.6)

Follow the specification.

Basis of Payment (Sec 805.7)

After seeding is completed, the contractor can request partial payment. Material certification and invoices must be provided to authorize the initial 80% payment. Additional payment for the seeding should be made when growth is obtained, with the exception of the winter months of November through February. Final acceptance of the seeding is to be delayed until the end of the 60-day or May 1 for winter seeding.

Winter Seeding

The winter exclusion period for seeding after September is included to ensure against a winterkill. This exclusion can create undue hardship on a subcontractor as a substantial expenditure is made with a possible 7-month delay for full payment. As the subcontractor can not predict the month of the year when final seeding will be necessary, the subcontractor must either bid risk and possibly lose the job or bid without regard to risk and absorb any loss due to the necessity of winter kill rework. Seeding done in October is less prone to winterkill than seeding performed in late November. It is recommended a percentage payment be made when acceptable winter growth is obtained. The following chart offers the recommended percentage of payments for winter seeding. Winter progress payments for seeding must not be made without verifying acceptable growth is present.

Seeding Percentages
85% 80% WHEN SEEDED 85% 90%

Note: Pay 80% when seeding is completed and 100% when final accepted. For the months, October through April, pay the percentages indicated by the table when acceptable growth is obtained. For months, May through September, pay 95% when acceptable growth is obtained.


When it is determined damaged areas is the department’s responsibility, the contractor is to be reimbursed for repairing the seedbed and reseeding as provided in Sec 109.4 of the Standard Specifications. A change order should be processed to document the additional work, as the charges are an overrun to the contract.