Soil quality significance of goat pens positioned on the hilltop of sloping cocoa farms in Polman-Sulawesi

Abstract Many smallholder cocoa farmers in Polman, West Sulawesi-Indonesia breed goats traditionally on hilltop of the sloped cocoa farms. The goat’s manure is deposited under the pens, not distributed on the farm. We investigated the significance of this traditional goat breeding on the hilltop of sloping cocoa farms on soil quality based on the distance from the pens along the slope direction. We selected three sloped-cocoa farms where this traditional model had been practiced for years. The farms studied had 30 to 70% slopes, clay loam to clay soil textures. Along a transect lane, 0-5, 5-10, and 10-15 meters from the pen on each farm, we measured soil bulk density, hydraulic conductivity (HC), soil organic carbon (SOC), pH, soil nitrogen, phosphorus, potassium, cation exchangeable capacity (CEC) and earthworm population. This traditional practice improved soil quality compared to the adjacent farms which were not affected by the practice (control). Soil HC, SOC, N, P, K and CEC, and earthworm population were markedly higher under this system compared to the control, especially at 0 to 5 m distance from the manure deposit. The beneficial effects of this system were limited only within 10 m from the pens, beyond which soil quality was practically similar to the control site. This traditional system may be considered as an appropriate practice for soil quality maintenance in sloping cocoa farm, but an improvement is needed for greater benefits and reduced risks through terrace construction and manure deposition every 5-10 m range along the slope.</jats:p

Soil Organic Matter, Mitigation of and Adaptation to Climate Change in Cocoa–Based Agroforestry Systems

Belowground roles of agroforestry in climate change mitigation (C storage) and adaptation (reduced vulnerability to drought) are less obvious than easy-to-measure aspects aboveground. Documentation on these roles is lacking. We quantified the organic C concentration (Corg) and soil physical properties in a mountainous landscape in Sulawesi (Indonesia) for five land cover types: secondary forest (SF), multistrata cocoa–based agroforestry (CAF) aged 4–5 years (CAF4), 10–12 years (CAF10), 17–34 years (CAF17), and multistrata (mixed fruit and timber) agroforest (MAF45) aged 45–68 years. With four replicate plots per cover type, we measured five pools of C-stock according to IPCC guidelines, soil bulk density (BD), macro porosity (MP), hydraulic conductivity (Ks), and available water capacity of the soil (AWC). The highest C-stock, in SF, was around 320 Mg ha−1, the lowest, 74 Mg ha−1, was in CAF4, with the older agroforestry systems being intermediate with 120 to 150 Mg ha−1. Soil compaction after forest conversion led to increased BD and reduced MP, Ks, and AWC. Older agroforestry partly recovered buffering: AWC per m of rooted soil profile increased by 5.7 mm per unit (g kg−1) increase of Corg. The restored AWC can support about a week’s worth of evapotranspiration without rain, assisting in climate change adaptation