Comparison of Alternative Seed Mixes to Standard TxDOT Specifications

Project Description

Researchers surveyed available native grass species and tested selected seed mixes under various roadside conditions to determine which might be desirable additions to the Texas Department of Transportation (TxDOT) current seeding specification. The project also investigated the effects of increased seeding rates of selected grass species and the effect of higher rates of compost-derived nitrogen fertilizers on plant growth and nutrient leaching.

Mixes comprised of commercially available native plant seed were tested on general soil types (clay and sand) and pH as found in and imported from west, south, east, and north Texas. Researchers also compared the standard TxDOT seeding rates to two increased seed rates used on recent construction projects.

Based on test results, the research team does not recommend the inclusion of an all-native seed mix as part of TxDOT practice as the Native seed mixes produced a lower percent cover of vegetation than the Standard Mix. Runoff from the two standard fertilizer applications and the organic compost-derived fertilizer application all fell within the acceptable limits for irrigation water. In all cases, the allowable parts-per-million were below accepted levels for irrigation water. During this study it was confirmed that quality of the soil used plays a more significant role in seed germination than quantity of seed sown. It is important that the soil used on a construction project is analyzed to ensure adequate levels of soil nutrients are available to the vegetation.

Researchers determined that current TxDOT vegetation establishment practices (including seeding) mirror the most widely accepted standards of practice used by agencies, programs, and practitioners throughout the United States. Applied as general rules and fundamental practice, these practices have been well-suited to meet the vast majority of vegetation establishment needs.

Project Publications

Comparison of Alternative Seed Mixes to Standard TxDOT Specifications 0-5212-S

Comparison of the Use of TxDOT Seeding Mixes and Fertilizer Rates to the Use of Native Grass 0-5212-1

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