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Last updated on 20 January, 2020

Improved terracing for enhancing soil fertility on sloping land

The terracing technology is a combination of vegetative and structural measures that address the soil, nutrient, and moisture loss problems associated with traditional outward-sloping land, which is reshaped into a series of level or gently sloping platforms across the slope to form terraces. Nitrogen-fixing hedgerow species and quality fodder grass species that bind the soil are grown along the newly established terrace-riser margins, which are constructed using soil-filled bags and other locally available materials. This low-cost technology is culturally acceptable, owing to which farmers have been motivated to replace maize crops with cash crops and fodder in their terraced fields.

The issue

The characteristics and challenges of mountain agriculture differ from those in the plains. In the mountains, crops are grown on sloping land that is mostly rain-fed. Pre-monsoon and monsoon rains erode the fertile topsoil and applied nutrients. Soil moisture in the sloping land doesn’t last long, as runoff is higher than infiltration. This is a major cause of the lower soil fertility and lower production of mountain agriculture compared to the plains’. The high intensity of rainfall leads to rill, sheet, and gully erosion, and landslides, which damage cultivated land and crops.

Traditional cultivation, like that shown in this photo, erodes the soil and depletes the nutrients in the ground

 

The solution

Terracing was demonstrated on six farmers’ fields in Kubinde Village of Nepal’s Kavrepalanchok District in 2002, and by 2014 the technology had been adopted by more than 90 percent of the households of Kubinde Village and surrounding villages. To develop the technology, the local line agency office of the Department of Soil Conservation and Watershed Management was involved, and their experiences and knowledge were incorporated in creating a validated technology that the department could use in its own programmes.

Before implementing the terrace-improvement work in Kubinde Village, a Terrace Improvement Committee was formed comprising local farmers, and committee members were then trained on sub-watershed management and soil and water conservation measures.

The major components of terrace creation included constructing riser walls made of empty cement bags filled with soil and stone. In a few cases, dried bamboo clumps were used. Terracing involves excavation of soil from the upper part of the field and using it to build the lower part behind the terrace riser wall, to create a level platform/bed. Grass and hedgerow species are then planted on the outward margins of the terrace risers.

Maintaining established terraces include smoothing the surface of land, rill, and sheet erosion each year caused by monsoon and pre-monsoon rains; slicing terrace risers once or twice a year; and maintaining the hedgerow/grass planted along the terrace margins, by cutting them regularly to keep them at a height of 50 cm.

Terracing technology reduces a field’s slope length and angle, so that soil erosion and soil fertility losses are minimal compared to a sloping land’s. The terrace’s flatness reduces runoff and enhances infiltration, which makes more moisture available to crops. Growing fodder along the terrace margins reduces drudgery, particularly for women and children, as grasses for cattle fodder become available near the households.

In 2003, ICIMOD estimated the establishment and maintenance cost of terracing based on 1 ropani (508.5 m2) of land, and that figure was extrapolated to a hectare of land. The total establishment cost was USD 1,287 and the annual maintenance cost was USD 342.

Impact and uptake

In the demonstration site, terracing led to increased production of maize, potato, and beans. Some farmers started growing vegetables and rice two to three years after the terracing, resulting in household income growth by 100 percent. In addition to crop production, the production and quality of fodder has also increased. The price of land increased considerably after the terracing, from USD$410 per ropani in 2001 to between USD 370 and USD 2,055 per ropani in 2006.

Initially, two adopters (out of six) of this technology shared the benefits with new farmers in their village and in the surrounding villages. ICIMOD revisited the village to observe the state of the technology 12 years after the initial demonstration and found that over the years, most farmers of Kubunde Village and surrounding villages had improved their sloping land. For a household, it took more than five years to entirely convert their sloping land into level terraces. Each household converted their land gradually, rather than at once, owing to financial and labour constraints. As of 2014, out of 350 households in Kubinde Village and surrounding villages, 329 households had adopted this technology.

Contributor

Madhav Prasad Dhakal, ICIMOD