Evaluation of several mulching methods used by different highway departments showed that 2 tons of grain straw per acre provided adequate protection to newly prepared and seeded 2½:1 backslopes when subjected to l‐year frequency storms, 1.3 inches of rain in 30 minutes. However, when subjected to a 10‐year frequency storm, 2.7 inches in 60 minutes, two treatments stood out as superior. These were “whisker dams”, called the Florida method, which permitted 41% runoff and 10 tons per acre soil loss; and surface mulch, called the Cartersville method, which permitted 40% runoff and 11 tons per acre soil loss.
In all cases where asphalt spray was a part of the treatment, the effectiveness of mulch was decreased when tested by the 10‐year frequency storm. Runoff and soil loss from mulch and mulch plus asphalt were 1.1. inches and 11 tons per acre and 1.3 inches and 32 tons per acre, respectively. Mulch mixed and mulch mixed plus asphalt were the same‐l.3 inches and 27 tons per acre‐indicating that the asphalt had no beneficial effect.
The California method was a checkerboard arrangement of straw pressed into the surface. This treatment was inferior to the “whisker dams” because the staggered arrangement permitted more soil transport by over‐land flow. Runoff and soil loss for these two treatments were 1.2 inches and 44 tons per acre and 1.1 inches and 10 tons per acre, respectively.
Bare, unprotected backslopes eroded at the rate of 97 tons per acre and permitted 62% runoff. Six months or more after planting, satisfactory stands had been established with all mulch treatments.
Synopsis
Crownvetch was established on highway cut slopes in the Piedmont Uplands of Georgia by seedings and transplantings made in the fall and early spring. Either mulch or a nurse crop on all slope and soil conditions was usually required to protect the seedlings in their early stages. Best protection was obtained when crownvetch was seeded in combination with Abruzzi rye as a nurse crop.
Synopsis
Erosion control can be secured on most steep roadbanks by establishing good vegetative cover of adapted species. Mulch aids this cover establishment and provides temporary erosion control until sufficient plant cover develops. Adequate fertilizer and lime hasten plant growth and cover. Proper mowing schedules aid seed production, plant vigor, and cover development.
Synopsis
Soil losses from actively eroding, steep, bare roadbank cuts in the hilly upper Piedmont of Northwest Georgia are excessive, and effective control has been secured on large numbers of similar roadbanks by establishment of certain adapted vegetative cover species, following adequate lime and fertilizer treatments and mulching where needed.
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