Pansak et al. (2008) found that minimum tillage and legume relay cropping practices
showed a positive yield response and helped to control soil losses within maize
cropping systems on moderate slopes in north-east Thailand, making such soil
conservation measures a viable alternative for tropical mountainous regions. However, SCTs application domain (including slope, soil type, soil fertility and weed
pressure) and effectiveness in reducing greenhouse gas emissions, as well as their
economic viability, still needs to be determined before their widespread application
can be recommended.
Contour-based cropping systems belong to those practices which are preferred
and most likely to be adopted by farmers (Subedi et al. 2009). They are
characterized by agricultural activities which follow an imaginary line drawn on
the surface of the land along which all points have the same elevation. In contourfarming farm operations, including plowing, planting, cultivating and harvesting
activities, are carried out along the contours, including contour tillage, contour strip
cropping and contour terracing. All these operations aim to avoid the concentration
of non-infiltrating rain, to guide surface run-off along gentle gradients and slowdown overland flow with the purpose of reducing soil erosion. In contour ditches, a
channel is excavated along the contour line to accumulate and spread the water
along its length. Further options include contour furrows, contour ridging and
contour stone rows. Contour furrows are established along the contour line to
reduce run-off and increase infiltration, whereas contour ridging is a ridge and
furrow tillage system which follows the contour lines. Contour stone rows can slow
down overland flow, increase infiltration and cause deposition of eroded material,
while contour based systems also include vegetated strips, such as contour grass
strips or contour hedges (ISSS 1996). In the Philippines, farmers have adapted
contour legume-based hedgerow farming practices into a simpler buffer-strip
system – as a labor-saving measure to conserve soil and sustain yields on steeply
sloping cropland. These natural vegetative contour buffer strips have proven suitable for farmers practicing low-input, biological organic farming, or farmers
practicing high-input conventional agriculture (Garrity 1999).
Soil cover plays a crucial role in erosion processes, as erosion increases with
decreasing soil cover (Dung et al. 2008; Pansak et al. 2008; Chaplot et al. 2005;
Podwojewski et al. 2008; Valentin et al. 2008). Mulching is a measure using plant
residues to protect the soil against rain splash and to maintain a favorable soil
microclimate by reducing evaporation (ISSS 1996). However, the introduction of
mulching practices appears potentially easier at sites where biomass production is
high enough to fulfill existing demands for feed and fuel, but may come to its limits
in regions with relatively high feed and fuel pressures (Valbuena et al. 2012). Thus,
farmers often see mulching as less appropriate, as it depends on the availability of
harvest residues or other plant materials, complicates weeding, and may attract rats
and snakes. As a result, it is often not adopted (Subedi et al. 2009). Synthetic or
biological geo-textiles also aim to reduce the direct rainfall impact on the soil by
increasing soil cover. Subedi et al. (2009) looked at adoption rates by farmers
within the Sustainable Highland Agriculture in Southeast Asia (SHASEA) project,
and found that polythene mulch was recognized as effective, but likely to be
7 Soil Conservation on Sloping Land: Technical Options and Adoption Constraints
233
showed a positive yield response and helped to control soil losses within maize
cropping systems on moderate slopes in north-east Thailand, making such soil
conservation measures a viable alternative for tropical mountainous regions. However, SCTs application domain (including slope, soil type, soil fertility and weed
pressure) and effectiveness in reducing greenhouse gas emissions, as well as their
economic viability, still needs to be determined before their widespread application
can be recommended.
Contour-based cropping systems belong to those practices which are preferred
and most likely to be adopted by farmers (Subedi et al. 2009). They are
characterized by agricultural activities which follow an imaginary line drawn on
the surface of the land along which all points have the same elevation. In contourfarming farm operations, including plowing, planting, cultivating and harvesting
activities, are carried out along the contours, including contour tillage, contour strip
cropping and contour terracing. All these operations aim to avoid the concentration
of non-infiltrating rain, to guide surface run-off along gentle gradients and slowdown overland flow with the purpose of reducing soil erosion. In contour ditches, a
channel is excavated along the contour line to accumulate and spread the water
along its length. Further options include contour furrows, contour ridging and
contour stone rows. Contour furrows are established along the contour line to
reduce run-off and increase infiltration, whereas contour ridging is a ridge and
furrow tillage system which follows the contour lines. Contour stone rows can slow
down overland flow, increase infiltration and cause deposition of eroded material,
while contour based systems also include vegetated strips, such as contour grass
strips or contour hedges (ISSS 1996). In the Philippines, farmers have adapted
contour legume-based hedgerow farming practices into a simpler buffer-strip
system – as a labor-saving measure to conserve soil and sustain yields on steeply
sloping cropland. These natural vegetative contour buffer strips have proven suitable for farmers practicing low-input, biological organic farming, or farmers
practicing high-input conventional agriculture (Garrity 1999).
Soil cover plays a crucial role in erosion processes, as erosion increases with
decreasing soil cover (Dung et al. 2008; Pansak et al. 2008; Chaplot et al. 2005;
Podwojewski et al. 2008; Valentin et al. 2008). Mulching is a measure using plant
residues to protect the soil against rain splash and to maintain a favorable soil
microclimate by reducing evaporation (ISSS 1996). However, the introduction of
mulching practices appears potentially easier at sites where biomass production is
high enough to fulfill existing demands for feed and fuel, but may come to its limits
in regions with relatively high feed and fuel pressures (Valbuena et al. 2012). Thus,
farmers often see mulching as less appropriate, as it depends on the availability of
harvest residues or other plant materials, complicates weeding, and may attract rats
and snakes. As a result, it is often not adopted (Subedi et al. 2009). Synthetic or
biological geo-textiles also aim to reduce the direct rainfall impact on the soil by
increasing soil cover. Subedi et al. (2009) looked at adoption rates by farmers
within the Sustainable Highland Agriculture in Southeast Asia (SHASEA) project,
and found that polythene mulch was recognized as effective, but likely to be
7 Soil Conservation on Sloping Land: Technical Options and Adoption Constraints
233