Contour Farming for Sustainable Management of Soil Erosion

Conventional contour farming or terracing helps keep soil loss to a minimum in hilly terrain. But in order to maintain yields, other equally important issues also need to be considered. Text and Photos by Henrylito D. Tacio

Davao del Sur, Philippines, 12 April 2017. In the early 1970s, American missionary Harold Ray Watson – then director of the Mindanao Baptist Rural Life Center (MBRLC) – received several reports of declining farm income from upland farmers in the Kinuskusan of Bansalan region, Davao del Sur. 

Watson discovered that in one area, corn production had dropped from 3.5 tons per hectare to about only 0.5 tons per hectare in a span of ten years. Other crop yields had also dropped 60% - 80% during the same period.

An agriculturist by profession, Watson did his own investigation and came to conclusion that the main culprit for these low yields was the depletion of soil and nutrients through erosion.

Example of Sloping Agricultural Land Tehnology in the Philippines

Example of Sloping Agricultural Land Tehnology in the Philippines

Soil erosion is an enemy to any nation – far worse than any outside enemy coming into a country a conquering it,” he said, decribing it as ‘an enemy you cannot see vividly.’ Watson, who received the prestigious Ramon Magsaysay Award in 1985 for international understanding said it was “… a slow creeping enemy that soon possesses the land.”

Degraded Soil

As form of land degradation, soil erosion is the most serious type, according to Dieldre S. Harder, a researcher with the Economy and Environment Program for Southeast Asia (EEPSEA). She estimated that soil erosion affects 63% - 76% of the country’s total land area, particularly in the upland regions.

“Around 74% of sloping upland area is cultivated for subsistence farming, which has implications on food security,” wrote Harder in her paper which was part of a research project titled “Sustainable Land Management: Adoption and Implementation Constraints.”

Crops with hedgerows

Crops with hedgerows

A.M. Van Oosten and E.J. Cahill, the men behind the Towards Integrated Soil Conservation title, wrote in 1986 that “it is more practical and economical to use management practices that minimize soil erosion rather than to allow erosion to reach the stage where restoration of eroded soil is necessary. It is essential that the productivity of these resources be maintained, especially where there is great population pressure on land resource.”

The EEPSE study, in cooperation with the Economics of Land Degradation (ELD) Initiative, went on to identify three sustainable land management (SLM) practices in the Philippines: agroforestry, organic agriculture and contour farming. And one of the most noted contour farming systems was the Sloping Agricultural Land Technology (SALT), developed by MBRLC. 

Looking for stability

“SALT establishes a stable ecosystem,” said Roy C. Alimoane, the current MBRLC director. “Double hedgerows of leguminous trees and shrubs between land strips prevent soil erosion and maintain water flows.” Using the SALT system, when a hedge is 1.5 to two meters tall, it is cut back to a height of 40 centimeters and the cuttings are placed in the strips between contour alleys to serve as organic fertilizer (green manure).

Roy C. Alimoane: SALT establishes a stable ecosystem

Roy C. Alimoane: SALT establishes a stable ecosystem

“The hedgerows provide permanent vegetative cover which helps conserve water and soil. Likewise, they improve soil and air temperature to levels which favor growth of different agricultural crops,” Alimoane said. This has proven to be a critical difference to previous methods; one study showed that a farm tilled by a traditional farmer has a hectare erosion rate of 1,162.4 metric tons per year over six years, whereas a SALT farm has an erosion rate of only 20.2 metric tons per year during the same period.

But despite the advantages of SALT-based contour farming initiatives in the country, most farmers are still not adopting the system. EEPSEA Director, Herminia A. Francisco cited six constraints in the adoption of contour farming among Filipino farmers. These are:

·     Technical difficulty. In standard contour farming, the common technical difficulty met by farmers is in the delineation of contour lines.

·     Low availability of suitable materials. The best suited plants for hedgerows are readily not available: Flemingia macrophylla, Desmodium rensonii, Indigofera anil, and Leucaena leucocephala are all difficult to find, and expensive.

·     High labour requirement. Contour hedgerows need to be trimmed regularly to avoid shading crops. This can be up to 30 persons-days per year.

·     Crop area reduction. If farmers follow the recommended one metre vertical distance between contour lines, the area lost for crop production barriers is around 20%-30% of the total land area.

·     No additional income. Farmers complain that they don’t get additional income for maintaining contour hedgerows. Non-monetary benefits like soil control and increased soil fertility have no obvious immediate value. 

·     Pest and disease host. There are reports that the hedgerows can play host to some pests and diseases.

Flemingia macrophylla hedgerows are great but hard to find

Flemingia macrophylla hedgerows are great but hard to find

And there are several other factors. For instance, subsistence corn farmers and those with higher off-farm income are less likely to adopt contour farming since hedgerows usually compete for labour from other non-farm activities. Also, lack of direct access to markets hinders farmers from introducing contour farming due to lack of knowledge on sustainable land management.

Group think needed

EEPSEA’s Francisco has suggested that a key group be established among farmers to encourage information exchange and discussion of SALT merits that could lead to increased adoption of the technique. Within a group, farmers can have access to a much wider scope of information on sustainable land management practices.

“Land degradation is also occurring in terms of reduced vegetative cover and loss of habitats, soil pollution, and water quality and quantity deterioration,” said EEPSEA in a statement. Which highlights the key issue: soil erosion is just one of the many aspects of land degradation. 

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