Application of Dynamic Model for Designing Zero Runoff System to Control Erosion in Cocoa Fields

Department of Agricultural Enginering, Faculty of Agricultural, Hasanuddin University, 90245, Makassar, Indonesia

^* Corresponding author: suhardi@unhas.ac.id

Abstract

Land degradation in cocoa plantations is mainly caused by surface runoff erosion. Surface runoff can be reduced by applying a Zero Runoff (ZRO) system. This system effectively reduces runoff when its size sufficiently infiltrates all surface runoff. This study aims to determine the size, dimensions, and location of a ZRO system that effectively increases infiltration and prevents surface runoff. The size and dimensions of the system were designed using a water balance approach, where all surface runoff is collected in the ZRO system and then infiltrated. Surface runoff was calculated using the Soil Conservation Services (SCS) method. The potential infiltration rate is a function of the soil's saturated hydraulic conductivity and the system's surface area. The saturated hydraulic conductivity of the soil was determined using the falling head method. The size and dimensions of the system were determined through model simulation based on field physical condition data using a dynamic model. The research results showed that the size and dimensions of the system depend on the amount of rainfall, the area of the catchment area, and the saturated hydraulic conductivity of the soil. From the dynamic model simulation, all surface runoff will be infiltrated if the dimensions of the zero runoff system are 1 x 1 x 0.5 m. This size can accommodate a water volume between 0 – 0,006 m³, so with a system depth of 1,000 mm, there is no surface runoff.