**4. Methodology**

214 Soil Erosion Studies

Hydroseeding is one of the methods of ground re-vegetation to stabilize bare soil surface to prevent soil erosion. It calls for the use of cellulose mulch material mix with a tackifier acting as binder. The cellulose binder mulch, together with the grass seeds, fertilizer and water are mixed inside the tank of hydroseeding machine to form into consistent and homogeneous slurry and then hydraulically sprayed to the ground. When sprayed, the cellulose fiber mulch together with the fertilizer and the grass seed will act as an absorbent mat, holding enough moisture to allow proper germination of the grass seeds and the same time forming a firm blanket cover to the soil surface even before the grass seeds germinates to prevent soil erosion. The cementitious geobinder forms a permeable curst on the soil surface which control water, soil and wind erosion. The geobinder is a non toxic cementitious binder that safely holds the grass seeds uniformly in place, prevents surface erosion and water evaporation in the soil. The cellulose fiber mulch which is biodegradable and in time will revert back to organic matter, enhances vigorous establishment of the grass ground cover. The application of hydroseeding process can be considered for temporary

Hydroseeding is now a widely used process of controlling soil erosion abroad. Countries like the United States use this type of grass planting since the process is fast, efficient, and economical. It is more effective than conventional seeding and more economical than conventional sodding. In the Philippines, hydroseeding is first introduced in the Subic-Clark-Tarlac Expressway Project. Reports show that the adoption of hydroseeding is advantageous to the said project. Centrocema Pubescens (Centro) and Calopogonium Muconoides (known as Calapo) are the plants used in the project. The application of hydroseeding method yields the following observations and conclusions: (a) Hydroseeding planting process is the fastest way of preventing soil erosion; (b) the temporary seeds will germinate forty-eight (48) hours after spraying and the planting seedbed of the embankment is already 100% stabilized even before the establishment of the permanent ground cover; (c) Aside from nursing the grass seeds, the planting seedbed stabilizer called "geobinder" holds the ground cover grass seed in place and other soil planting amelioration materials; (d) Less watering is needed once the ground cover grass seed is 100% established; (e) The mulch material serves as moisture retention absorbing mat and at the same time reduces the development of the undesirable weeds; (f) In hydroseeding, 10,000 to 15,000 square meters of planting seedbed can be accomplished in a day; (g) There is no rill or gully erosion in case of heavy rain once hydroseeding is in place; (h) The Pure Living Seed (PLS) population per square meter is guaranteed to be 70-75 Living Grass Seed; (i) Hydroseeding final end product will require only very little maintenance once the permanent ground cover is purely

Coconets are made from 100% coir fiber twine woven into high strength nets for extreme slope stabilization, protection of high velocity stream banks and high velocity intermittent flow channels. The natural coconut coir material perform very well in applications such as erosion control blankets for landscaping. The mesh of woven coconut coir matting acts as miniature dams that prevents the seeds or seedlings to be washed away by rain and wind and facilites the growth. The netting breaks up runoff from heavy rains and dissipates the energy of

**2. Hydroseeding** 

established. (BCDA, 2006)

**3. Coconets** 

and permanent erosion control, seeding and mulching.

To represent the slope covered with combined Hydroseeding and coconets, test boxes were constructed sloping at 65 degrees and having a surface area with dimension of 106 cm long by 63 cm wide as shown in Fig. 1. Three (3) trial boxes were constructed. The test boxes were covered with soil. These test boxes covered with soil only were all initially subjected to artificial rainfall simulator for the bare soil tests. After the bare soil tests, the test boxes were covered again with soil and covered with combined hydroseeding and coconets for another three (3) sets of samples. Vegetation was allowed to flourish for 21 days before subjected to the rainfall simulator.

Fig. 1. Dimensions of the test box.

Combined Hydroseeding and Coconet Reinforcement for Soil Erosion Control 217

When established, it forms as an umbrella to dissipate rain drops impact and is

Airtol geobinder is a low cost cementitious binder used in the study. When mixed with water and mulch, this geobinder sets in a predictable way to form an erosion resistant crust. Packed in 22.8 kilo bag, it is produced from high quality gypsum and is (fully) imported

The cellulose fiber mulch is manufactured and processed from recycled paper. Made in

This is a by-product of coco fiber consisting of short coco fiber and dust available locally.

To enhance the growth of plants, chemical grade fertilizer, in accordance to Bureau of Soil Recommendation, is added in to ameliorate common soil nutrient deficiencies. It is an organic fertilizer locally produced in palletized form that is both environmental friendly and

To maintain good vegetation, the soil must meet certain requirements as a growth medium.

a. enough fine-grained (silt and clay) material to maintain adequate moisture content usually 15-20%. This is based from Unified Soils Classification System (ASTM

e. sufficient pore space to permit root penetration and it will be done by not compacting

The soil used was sieved to separate large stone and other unnecessary things not needed. For every layer of 10 inch, the soil in the test box is compacted with use of ply board, a piece of wide flange or bricks. Compaction is done by placing the ply board on top of each layer to

Water Holding Capacity - 100 grams DW/will hold 1,000 grams of water.

environmental friendly and low - maintenance.

Seed Purity - 85%

**4.2.2 Geobinder** 

from the USA.

**4.2.4 Cocopeat** 

**4.2.5 Fertilizer** 

non-toxic.

**4.2.3 Cellulose fibre mulch** 

USA, it is packed in 50 lbs. bag.

**4.3 The soil for the test box** 

Designation D-2487);

the last 4-6 inch of soil.

It should meet the following conditions:

b. sufficient depth of soil to provide an adequate root zone; c. favorable pH range for plant growth which is usually 5.5-6.0 ; d. soil must be compacted like natural conditions soil slope; and

Moisture Content - 15% Organic Matter - 99.5% pH Level - 5.5 to 6.0%

Packed in 15 kilo bag, this acts as a soil conditioner.

Adaptability - Tropical

Permanent ground cover grass seed - Centrosema (Pubescens)

Temporary grass nursing seed - White Millet

Germination - 80 to 90% average

The amount of soil splashed out by runoff from the containers were collected and weighed. The data collected were used to compare erosion in mere bare soil to that with combined hydroseeding and coconet as slope protection.
