Seeding of Erosion Control Projects

Agdex#:	751
Publication Date:	11/90
Order#:	90-231
Last Reviewed:	11/90
History:	Revison of Factsheet "Seeding of Erosion Control Projects", May 1985
Written by:	Robert Stone - Engineer/OMAFRA; Harvey Wright - Plant Industry Branch/OMAFRA

Table of Contents

1. Introduction
2. Types of Projects Requiring Vegetation
3. How Does Vegetation Prevent Erosion?
4. Types of Grasses and Legumes Available - Which Ones to Use?
5. Fertilizer for Grassed Areas at Seeding
6. How to Apply
7. When to Apply
8. Herbicide Problems
9. Maintenance
10. Assistance

Introduction

A vegetative lining is a very necessary component in many erosion control projects. The successful establishment and maintenance of this lining often makes the difference between success and failure.

Types of Projects Requiring Vegetation

1. Open Channel Banks
2. Grassed Waterways
3. Other non-tilled areas such as steep slopes, berms and buffer strips.

How Does Vegetation Prevent Erosion?

1. Prevents soil particle detachment by rainfall impact.
2. Resists eroding forces of overland flowing water.
3. Creates more resistance to overland flow and consequently reduces it's velocity.
4. The root structure improves the infiltration capacity of the soil which will reduce total overland runoff.
   

Types of Grasses and Legumes Available - Which Ones to Use?

Almost every seed company has specific seed mixture recommendations for different applications based on the drainage of the soils, tolerance to shade, tolerance to high traffic conditions, resistance to flow velocity, maintenance requirements, climatic conditions, available time to establish, and whether it is to be a permanent cover or a livestock feed.

The following forage species do a good job of providing cover:

1. Tall Fescue at 22 kg/hectare
   • tolerate a wide range of drainage, from poor to droughty
   • forms a very tough sod, fairly quickly
   • grows through dry summer weather, stays green
   • should be clipped once or twice per year
   • not very palatable livestock feed
     
     
2. Creeping Red Fescue at 20 kg/hectare + Bird's-foot trefoil (Empire) at 12 kg/hectare
   • tolerates fairly wet to droughty locations, and shade
   • somewhat slow to form sod, but strong sod when established
   • usually does not require mowing
   • reasonably good quality hay can be produced
     
     
3. Timothy at 7 kg/ha + Bird's-foot trefoil at 10 kg/hectare (wet soils) or Timothy at 5 kg/ha + Alfalfa at 11 kg/hectare (well drained soils)
   • often used when the rest of the field is being seeded to forage at the same time as the grassed waterway.   When the forage field is plowed down, leave the waterway unplowed.
   • will need to be mowed at least twice per year. Provides good livestock feed if baled for hay.

Under most conditions, grasses can be used as erosion-resistant cover for water velocities up to 1.5 meters per second. Above this speed, other types of linings should be considered such as rock riprap or underground pipes.

Fertilizer for Grassed Areas at Seeding

To ensure a quick thick stand, the application of fertilizer is essential. The following types and rates should be used.

• On sandy loam soils use 6-24-24 at 300 kg/ha
• On clay loam soils use 8-32-16 at 300 kg/ha

These rates may seem high. However, the total grassed area is usually not that large. Ideally the fertilizer should be broadcast and worked in fairly shallow (70 to 80 mm) in the final stages of seedbed preparation.

If grass mixture (1) is used, broadcast an additional 125 kg/ha of ammonium nitrate when the grass is 50 to 80 mm tall.

How to Apply

Several methods can be used as follows:

1. Hand cyclone seeding followed by harrowing and cultipacking (if possible). This method randomly distributes the seed avoiding any rows of grasses being created. Problems with establishment due to poor depth control may exist. The cyclone will seed areas which are inaccessible to machines such as ditch banks and steep slopes.
   
   
   
   
   Figure 1. View of hand cyclone seeding operation. Two applications (preferably perpendicular to each other) should be completed to ensure complete coverage.
   
   
   
2. A grain drill with seed box is another method. If a fertilizer box is on the drill it can be used to incorporate the fertilizer at the same time. Unless wet conditions exist, cultipacking after seeding should be completed to firm the soil around seeds for faster, evener germination. A double weave method of seeding may avoid the straight row problem (Figure 2).
   
   
   
   Figure 2. Sketch showing pattern created when using a double weave method of seeding. Note that the highest concentration of seeds is placed in the centre of the waterway where the erosive forces are the greatest.
   
   
3. A "brillion" seeder also works well. Fertilizer will have to be incorporated before seeding. If a quick thick stand is required under difficult conditions (such as steep slopes or poor timing) hydroseeding should be considered. Hydroseeding is the application, under pressure, of seed, fertilizer, mulch and water. This method is normally more expensive than the above methods.
   
   
   
   Figure 3.  View of a hydroseeding mixture being applied to a recently constructed ditchbank.
   
   

   Seeding should occur on the day the soil is disturbed if possible. This will maximize the available moisture for seed germination. Mulching using straw or hay at the rate of 3-5 tonnes/ha may be required to retain heat and/or moisture during critical periods.

When to Apply

The time of seeding is important. Under average conditions, the following chart indicates the probability of seeding success versus the time of seeding for both hydroseeding and hand seeding. This represents average Ontario conditions. For certain areas the time frame may change slightly, however, the rest of the graph should stay the same.

Figure 4. Probability of seeding success versus time of year for two types of grass applications.

Text equivalent

The application of straw or hay mulch and irrigation during dry periods will increase the probability of success.
In addition, there are numerous artificial products available which add expense but should increase the probability for success under certain conditions. These should only be considered where optimum timing cannot be met.

Forage grasses seeded in September will establish, but will not give a very tough sod by winter and may not be able to hold the soil during spring runoff. Seeding of fall wheat with the grasses will give a much tougher cover for fall and early spring water runoff. At more vulnerable areas the application should be doubled for added protection. The wheat should be clipped about mid-spring as it starts to shoot, to allow more light into the seedling grasses. With late fall seeding (not recommended), fall rye is better than wheat, but will be more competitive with grass seedlings the following spring.

If forage legumes are being seeded as part of the mixture, they must be seeded by mid-August to become well established. Later seedings of legumes usually winterkill.

An alternate where the construction is not completed until fall is to seed only the wheat or rye in the fall, and broadcast the grass seed mixture in early spring after the main runoff.

With spring and summer seeding on vulnerable areas, there can be an advantage to seed oats with the grass seed mixture, at about 40 kg/ha, to form a "sod" more quickly. The oats should be mowed as soon as they start to shoot. Two clippings may be necessary.

Herbicide Problems

1. Most herbicide damage to waterways, either on seeding year or later, is caused by spraying right across the waterway, especially with atrazine. This must be avoided. On spring seeded areas, the use of atrazine on the surrounding fields should be avoided, if possible.

2. Any of the grass herbicides in corn (Sutan, Dual, Bladex) will kill out spring seeded areas if directly sprayed. However, if an area is sprayed in the spring, normally the spray will have broken down enough to allow late summer or early fall seeding. The same is true of the soybean herbicides such as Dual and Sencor. On dry years, the soybean herbicide, Treflan, if used at the high rate, in the spring, could still cause damage to a fall seeded mixture.

3. There is always the possibility that heavy rains and sheet erosion could wash enough of a preemerge or postemerge grass herbicide, or atrazine, into the grassed area to cause injury. This depends on whether the silt and herbicide stay in the waterway or move on. In general, preplant incorporated herbicide has less potential to move and should be considered in vulnerable situations.

4. If mixture (2) or (3) (see earlier section on types of grass) is used, do not spray across the waterway when spraying corn postemerge with Banvel, Kilmor, 2-4D, MCPA or Laddok. Mixture (1) can be sprayed through with Banvel, Kilmor, 2-4D or MCPA.
   

Maintenance

Areas seeded in grass require on-going maintenance and certain precautions.

1. They should be mowed at least once but preferably 2 or 3 times per year.
2. They should periodically be fertilized and re-seeded to fill in bare spots.
3. Heavy traffic should be minimized especially during wet periods to prevent compaction and rutting.
4. Weeds should be controlled.
   

Assistance

Assistance is available from the Ministry of Agriculture, Food and Rural Affairs. Qualified erosion control contractors are also available to assist on the design and construction of erosion control projects. The local offices of the Conservation Authority may offer both technical advice and construction supervision. Also, a consulting Engineer could be hired for design and supervision.