Evaluation of Effects and Alternatives of Terrace Riser Slicing Practice in Nepal

By Gandhiv Kafle and Prof. Mohan K. Balla
July 2005

Mr. Gandhiv Kafle is the Program Coordinator for the Nepal Wetland Research Group (NWRG), Institute of Forestry, Tribhuvan University in Pokhara - Nepal. Prof. Mohan K. Balla teaches at the Department of Watershed Management and Environmental Science of the same institution.

The study was carried out in Paundi Khola Sub-watershed of Lamjung District, with the objective of evaluating the effects of terrace riser slicing practice and it´s alternatives. Terrace riser slicing height and signs of erosion were recorded through field observation and direct measurement. Key informant´s survey, semi-structured walk and focus group discussions were also undertaken to acquire relevant information on positive and negative effects of slicing practice, perception of farmers on different issues and possible alternatives of terrace riser slicing. Significant signs of erosion and its effects were not observed up to 1m sliced riser height. But beyond 1m the erosion signs appear significantly. The more the slicing height, high is the erosion and vice-versa. . Farmers perceive that benefit of keeping natural grasses on terrace riser is less than slicing them from the riser. Farmers believe that cutting the grass foliage periodically and partial slicing (low height of riser) may be good technique to keep grasses on terrace risers and edges without inducing soil loss and insect pest problem.

Key words: Effects, terrace risers, slicing, erosion, alternatives, improved varieties

Introduction

Soil conservation is an important requirement in sustainable farming. Basics of soil erosion control are to reduce detachment and transportation capacity of the eroding agents (water and wind) through different agronomic, vegetative measures generally known as conservative measures (Amatya and Shrestha, 2002). Good crop husbandry is an effective soil conserving practice (Joshi, 1992). Grasses are generally used to reduce soil erosion. Grasses develop rapidly and produces humus also. They can recover from damage and completer burial.

Nepalese farmers have been using several soil and nutrient management activities, such as use of farm yard manure (FYM)/compost, terracing, slicing the wall of terrace riser, leaf and in situ green manuring, shifting herds for in situ manuring, use of legume crops in cropping system etc. Nepalese farmers have recognized the value of terraces as the major precondition for the maintenance of soil fertility. The existing bench terrace systems found in Nepal are a trademark of the Nepalese farmers´ determination to maintain their agricultural systems. Terrace risers can be stone-lined, vegetated or purposively cut to bare soil. Extremely stony soils will have stone-lined risers. Risers on stone-free phyllitic soils (in rice production) are kept free of any vegetation. Most terrace risers, however, are vegetated, either naturally or more recently, planted with improved grasses to provide significant quantities of fodder to the farmers.

Grasses have dense root mat, which intercepts rainfall and minimizes surface erosion. The roots develop rapidly and produce humus (Amatya and Shrestha, 2002). The grass cultivation on barren terraces and terrace risers and bunds of agricultural land is effective in reducing erosion hazards for hill farming to maintain the nutrient balance under different land-use systems. One of the practices used traditionally by the farmers in mid hills is terrace riser slicing. Wherever stone free condition exists, the farmer, as part of his overall terrace management system, slices 1 or 2 cm from the terrace (Carson, 1992). The farmers reported that slicing the terrace wall practice prevents collapse of the riser in the monsoon, adds fertile soil to the terrace below, and minimizes insects, disease, and rodent problems But this practice increases soil erosion (Joshi, 1992).

The measurement of slicing height of risers and record of signs of erosion will help to correlate them and decide appropriate or effective slicing height to minimize soil erosion. The present study was carried out to evaluate the effects of terrace riser slicing and alternatives of this practice in Paundi Khola Sub-watershed, Lamjung district, Western Nepal.

Materials and Methods

Study Area

The study was carried out in the Paundi Khola Sub-Watershed (28° 05´ and 28° 12´ 30" N latitude and 84° 17´ 30" and 84° 27´ 30" E longitude) in Lamjung district, Gandaki zone in the Western Development Region. It is 22 km south-west from Besisahar, headquarter of Lamjung district. It occupies an area of 5877 ha. Its elevation ranges from 500 m to 2000 m.

The major occupation of majority of people is agriculture. Paddy, maize and millet are the main cereal crops in this sub-watershed. The farming system is traditional that´s why the production is very low. Mango, Jackfruit, Nepalese hog plum, Banana and Pears are the main deciduous fruits cultivated by the farmers. Duradanda, Chandresor, Dhuseni and Sundarbazar are the main production area of citrus fruits e.g. orange, lemon, Sweet or malta orange etc. Only 29.7% people produce food sufficient for the whole year whereas 21% people hardly produce food sufficient for less than 3 months from their own. 1.8% of total HH have land less than 5 Ropani. Total livestock number is 15592 with cows 4045, buffalo 4663, and sheep-goat 6884. Livestock number per HH is 5.7. Most of the livestock are of local breeds.

69.11% land area of this sub-watershed is cultivated whereas 30.89% land area is covered with forest. Sloping terrace covers 2063 ha and level terrace with 1999 ha. The main tree species found are Schima wallichi, Castanopsis indica, Alnus nepalensis, Pine species and Rhododendron species. The farmers have cultivated the improved varieties of the grasses like Napier (Pennisetum purpureum), Molasses (Melinis minutiflora) and Stylo (Stylosanthes guianensis) in the Paundi Khola Sub-Watershed area (Pandit, 2002).

Methodology

Relevant biophysical and socio-economic information was collected using both primary and secondary sources. Primary data was collected through direct measurement, field observation, questionnaire surveys, semi-structured walk and focus group discussions. During the field observations carried out in October-November 2004, slicing height of terrace riser and signs of erosion, perception of farmers and alternatives of this practice were studied and recorded. A reconnaissance field survey was made and then the questionnaires and data entry forms were developed compatible with field condition.

50 terrace risers of different height were randomly chosen and measurement was confined to those risers only. A checklist was designed to elicit information on positive and negative effects of terrace riser slicing. Semi-structured interviews were then conducted to collect information not obtainable through field observation. Relevant secondary data and information regarding the study area were collected from the District Soil Conservation Office, Lamjung and Institute of Forestry, Pokhara, Nepal.

The collected data were organised, tabulated and analysed later by using appropriate statistical tools such as percentage, mean etc.

Findings and Analysis

Perception of the farmers on terrace riser slicing

A checklist of issues on terrace riser slicing was prepared and informal small group discussion and semi structured walk were conducted to obtain the perception of the farmers on terrace riser slicing. The findings are as follows:

  1. Terrace riser slicing practice is unavoidable but the quantity (height) of slicing can be minimized.
  2. The soil erosion depends upon the height of the riser sliced. The more the slicing height, the more the erosion and vice-versa.
  3. Benefit of keeping natural grasses on terrace riser is less than slicing them.
  4. Cutting the grass foliage periodically and partial slicing (low height of riser) may be a good technique to keep grasses on terrace riser and edge without inducing soil loss and insect/pest problem.
  5. A combination of improved varieties of grasses and natural grasses helps to conserve soil and moisture more effectively than single-use on any land-use.
  6. Improved varieties of grasses fulfil the need of forage in dry or off-season.

Height of terrace riser slicing and signs of erosion:

50 different samples of Khet were randomly selected in the watershed and the height of slicing was measured. Erosion signs were noted for a range of terrace slicing height. In the study area, 56% of the terrace risers were of height 50-75cm, 18% with 75-100cm, 12% with 100-125cm, 10% with 125-150cm and only 4% with 150-175cm. Farmers practiced slicing the whole height of risers except in stony risers. No significant erosion signs were observed and it seemed natural in risers sliced to 50-75 cm measured vertically above the ground surface. Soil was detached from upper part of riser and added to terrace but no significant damage was observed in risers sliced to 75-100 cm above the ground surface. The amount of soil detachment gradually increased and hollow with water leakage was observed at some places in risers sliced 100-125 cm above the ground. Slicing the risers 125-150 cm above the ground affected the edge of upper terrace. More water leakage and signs of rill erosion were observed. Slicing 150-175 cm above the ground seemed the most hazardous where stones/gravels were observed on eroded portion.

Conclusions

Terrace riser slicing practice is unavoidable but the quantity (height) of slicing can be minimized. Farmers perceive that benefit of keeping natural grasses on terrace riser is less than slicing them from the riser. Farmers practice slicing whole length of risers except in stony risers. Significant signs of erosion and its effects were not observed up to 1m sliced riser height. But beyond 1m the erosion signs appear significantly. It is therefore concluded that the soil erosion depends upon the height of the riser sliced. The more the slicing height, high is the erosion and vice-versa. So it is recommended to slice the terrace riser up to 1m upward from the ground level. Farmers believe that cutting the grass foliage periodically and partial slicing (low height of riser) may be good technique to keep grasses on terrace risers and edges without inducing soil loss and insect pest problem. But it has not been practiced yet in the study area because farmers do not want to take risk of insect pest problem. So trial plots should be established in the study area and the practice of cutting the grass foliage periodically and partial slicing of terrace risers should be evaluated. Moreover, further research should be conducted to assess the economics of grass growing on terrace risers.

Acknowledgements

The authors are thankful to NARMSAP/DANIDA, Western Regional Office Pokhara for financial support. The paper is based on research project paper submitted by the first author to Institute of Forestry, Pokhara, Nepal for the partial fulfilment of Bachelor Level of Science in January 2005.

References

  1. Amatya, S. M., and Shrestha, K. L. (2002). Nepal Forestry Handbook. FAO, Italy, Rome.
  2. Carson, B. (1992). The land, the Farmer and the Future: A Soil Fertility Management Strategy for Nepal. Occasional paper no. 21. ICIMOD, Kathmandu, Nepal.
  3. Joshi, R. B., (1992). Indigenous Practices of Soil and Water Conservation in Farmlands. A Case Study of Bishnu Village Development Committee, Kathmandu, Nepal.

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