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to contour lines by the aim to drain the excess of water and prevent the tuberroot plants decay. This pattern of land management is prone to erosion especially in the initial phase of
farming practices. A general rule of thumbs is that water flow is perpendicular to contour lines. As a
consequence, when tillage is perpendicular to the contour lines, soil transport increase exponentially Blanco Lal, 2008. Thus, the challenges facing these farmers is how best to
manage their land in order to minimize soil loss at an affordable cost. Actually, numerous soil conservation techniques have been implemented but in general were failed to solve the
problems. Some of the reasons are : economically and socially not feasible, and technically not suitable with the local condition Critchley, 1991.
Addressing the problem, the research was conducted by implementing silt-pits to control erosion and sedimentation in sloping land. Silt-pit is close-ended ditch, dug between
plantation rows, to cut the slope length to smaller catchments, collect run-off and nutrient- rich sediments and redistribute eroded nutrients back into the soil Bohluli et al., 2014;
Moradi et al., 2015; Ping et al., 2012. This research was aimed to examine: 1 the capability of silt pit in controlling erosion and sedimentation and 2 the potential of silt pit as a learning
tool for farmers to comprehend the risk of improper land management practices and how to solve the problems. In their research in Malaysia, Bohluli et al. 2014 and Murtilaksono et al.
2011 concluded that silt pit reduced overland flow and soil erosion effectively. However, although silt pits have been implemented for several decades, there have been only a few
information determining the effectiveness of silt pits, particularly in high rainfall areas Bohluli et al., 2014.
2. METHODOLOGY 2.1 Site description
The study sites were situated in two sub village in Tinggi Moncong Sub District, the District of Gowa, South Sulawesi Province. The first location was in Bulubalea Sub Village, The
Village of Bulutana, and the second was in Datara Sub Village, The Village of Gantarang. Geographically the research site were located in 119
o
50’00’’ E – 119
o
54’00’’ E and 05
o
14’00’’ S – 05
o
18’00’’ S. Meanwhile, in the watershed system, the research sites were located in the upper part of Jeneberang Sub Watershed. The average precipitation was 3.000 mmyear.
Figure 1: Map of the Research Site
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2.2 Method 2.1.1 Measurement of rainfall, erosion and sediment
The small plots-based research was conducted to measure the effectiveness of silt-pits,- low- cost soil and water conservation instrument, easily implemented and maintained by small
farmers employing local resources-, in controlling erosion and sedimentation. The area of plot measurement unit was 2 x 5 m
2
. In this research, silt pits were implemented in horticulture plantation area in two slope levels: 8 and 15. There were six plots and six silt-pits with
sticks in each slope. The dimension of the silt pit was 2 x 0,5 x 0,3m of length, width, and depth respectively. To measure the trapped sediments, eight painted white sticks were
embedded in every silt pit perpendicular to silt pit floor. The diameter of each stick was 1cm and the height was 1 meter. The stick was drawn with scale to enable easy measurement. The
placement of silt pits of each slope and sticks are presented in Figure 2 and Figure 3.
Figure 2: Pattern of Silt-pits placement
Figure 3: Stick Placement
Contour line 2 m
5 m
2x5 m2
2 m
1 2
3 4
5 6
Original soil surface
Scaled Stick Trapped Sediment
TOP VIEW
FRONT VIEW
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The data collected in this study were rainfall, erosion, and nutrient content of the sediment. Rainfall was measured by a rain gauge unit, an automatic rainfall recorder ARR installed
closed to the plots. The magnitude of erosion was approached by measuring the trapped sediment in the silt pits. The observations of rain and sediment were done at 7.00 am every
day after rain day. The sediment volume was calculated by measuring the average height of sediment heap on sticks. The extent of the plots was relatively small, thus to the erosion
occurred in the plot was considered equal to the amount of sediment deposited in the silt pit. To determine the nutrient content in the sediment reflecting the nutrients loss, certain amount
of sediment samples were analyzed in the laboratory.
2.1.2 The use of silt-pit as a learning tool Since three decades ago, soil management and conservation efforts have been moving toward
a more Participatory Approach FAO, 2000. There were evidences that the most effective way to enhance farmers understanding of complex issues is learning by doing, action
learning, experiential learning and discovery learning Hagmann et al., 1997. Those such participatory approaches have been designed to enhance farmers´ inherent skills, knowledge
and capability to develop and disseminate their own technologies FAO, 2000. In many region, experiment-based participation was developed to generate farmer participation on soil
conservation effort Hagmann et al., 1997. However, participation will be generated only if the activities will produce clear and significant benefits within a short time in return to their
investment of time, effort and other inputs FAO, 2000; Morgan, 2005
In this research, plots with silt-pits were functioned not only as a tool for controlling and measuring erosion and sedimentation as well, but also employed as a learning tool for farmer
to comprehend the phenomena of erosion, sedimentation and how to control. Using this tool, the knowledge of farmers will be enhanced. Learning processes were started from the
development of silt-pit, stick installment, every day silt-pit observation, and sediment heap measurement. Instead of being taught theoretically with conservation techniques, farmers are
challenged to observe their situation, to simply analyze the cause and effect of observed phenomena, and try to develop their own ideas.
3. RESULT AND DISCUSSION 3.1 Silt-pit as a tool for controlling erosion and sedimentation
