CONTENTS-
Abstract
Introduction
Material and Methods
Results and Discussion
Conclusions

The institute had developed a number of non-woven jute geotextiles for various applications in biotechnology. An attempt was made to study the effect of using different eco-friendly materials as soil cover for erosion control and residual moisture retention in the hilly slopes of Andaman island which suffers from the soil erosion to the extent of about 10-15 tonnes/ha/year. In order to conduct field experiments a land with an average slope of 30-40% was identified. Four eroded grass lands were selected for application of different geomaterials for soil cover viz. (i) geo-mat, (ii) jute sack, (iii) coir rope matting and (iv) control. Geo-jute matting of 3000 gsm basis weight was layered over one of the thinly grassed plot of land.

After each shower the representative samples of run off water as well as soil samples at depth of 10, 20 and 30 were collected from each plot for determining the soil moisture content under different applications of soil covers. Soil cover with bio-technical geo-non woven jute showed significantly high value while higher moisture content in the soil profile (upto 30 cm depth), after rainfall resulted in significant loss of soil and water compared to jute sack and coir matting. The geo-jute was found much effective in reducing soil loss and enhancing in-situ conservation of rain water compared to other treatments.

The characteristic hilly undulating topography coupled with high annual rainfall (3100 mm) induces soil erosion to the extent of about 10-15 tonne / hectare / year in the islands therefore necessitating developing and adopting suitable soil conservation measures. Moreover   the water retention capacity of the soil being low, the soil moisture available for the crops is quickly deleted after cessation of rains. Hence, a n attempt has been made to study the effect of application of different eco-friendly materials as soil cover on the extent of soil erosion and residual moisture content in the hilly slopes of Andaman Island.

A sloppy land with an average of 30 0 - 40 0 was utilised for the study. Four different areas were selected for the use of different eco-friendly materials as soil cover. The treatments included different soil conservation materials as soil cover treatments. The treatments included soil conservation materials such as (i) Geo-Jute non-woven (ii) Jute woven (iii) Control

Geo-Jute woven with density of about 300 gm/m 2 was spread over   the thinly grassed slopey areas. The adjoining widths were overlapped suitably and fastened with jute thread / wooden pegs were driven all around the corners of geo-mat at appropriate distances to hold the mat in place. Similar technique was adopted with coir netting and double layered used jute woven fabrics. The adjoining thinly grassed slope was left as such for control purposes.

The vegetation coverage percentage was also measured from each plot after each shower, especially after cessation of rain, in relation to particular interval of time.

The observation for erosion control for Andaman in relation to vegetation cover (%) under different geo-textile with time is given in Table-1. From this table, following important observations could be made.

Excellent growth of grass geo-mat compared to Jute woven and Coir woven in the area, which was initially covered under sparse grasses.

The biodegrading of geo-jute non-woven is significantly faster under the humid tropical climatic conditions of these islands (i.e. within 7 months) compared to normal conditions in main land in 2 years maximum.     

The infiltration and percolation of precipitation, which is an important criterion for reducing soil and water loss in hilly area, was significantly higher under geo-jute non-woven compared to other treatments.

The high moisture content in the soil profile (upto 30 cm depth) after rainfall resulted in significant soil and water loss under this treatment as compared to jute woven and coir woven fabrics.

The geo-jute was effective in reducing soil loss and enhancing in situ conservation of rainwater compared to other treatments.

The vegetation cover percentage was also increased in all treated areas in relation to time compared with control area as depicted in Table-1.   The vegetation cover percentage was observed   after 80 days,   -   Jute nonwoven 90%, Jute woven – 66%, Coir woven – 57%, compared to control area (without fabric)-28%. This was due to ability of the natural fabric like jute, coir to absorb water and to degrade with time (one of its prime properties), which give it an edge over control area (no-fabric). The drapability and porosity factors of natural non-woven geotextiles allow it to conform closely to the terrain which is more advantageous compared with jute and coir woven fabrics i.e. ability to comply to the contours of the slope and staying in intimate contact with the soil.

Table-1 Case Study for erosion control for Andaman in relation to vegetation cover (%) under different geotextiles with time.

The geo-jute non-woven is very effective for enhancement of vegetation cover compared to other treatments thus to control erosion of slopey land.

National Institute of Research on Jute and Allied Fibre Technology (I.C.A.R)
12, Regent Park, Kolkata – 700 040. India.
Ph. No. 033-421-2115-6-7
E mail: asokmajumdar@yahoo.com