Effect of Organic and Inorganic Amendments on Productivity of Cocoa on a Marginal Soil in Sulawesi, Indonesia

Abstract

SUMMARYReduced soil fertility and damage from pests and diseases have contributed to a decline in productivity of cocoa (Theobroma cacao L.) smallholdings in Sulawesi, Indonesia over the last decade. In a trial on a marginal, acidic soil in South Sulawesi, young PBC123 cocoa trees were supplied with compost, mineral fertiliser (NPK fertiliser and urea) or dolomite, alone and in combination. After 20 months, the trees supplied with compost were taller, flowered more profusely and had a five-fold higher dry bean yield than other treatments. Treatments had no impact on incidence of cocoa pod borer, Phytophthora pod rot and vascular streak dieback. All of the trees supplied with compost survived, while the control, mineral-fertiliser- and dolomite-treated trees had a mortality rate of 22–45% and symptoms of interveinal necrosis. Leaf concentrations of N, P and K were within the normal range in all treatments. In the control and mineral fertiliser treatments, leaf concentrations of Ca (0.28–0.30%) and Mg (0.11–0.15%) were deficient, but were higher in trees supplied with compost (0.78–1.21% and 0.26–0.29%, respectively). The Mg/K ratio in soil-exchangeable cations and leaves was increased three-fold by the combined compost/dolomite treatment. Supplying mineral fertiliser alone resulted in 3.3 cmol kg−1 exchangeable Al, compared to 2.2 cmol kg−1 in control soils. Since 10 kg tree−1 year−1 compost was supplied, a rate that is not practical on most cocoa smallholder farms, further investigation of cost-effective applications of organic matter in conjunction with appropriate formulations of inorganic fertilisers is recommended.

Supplementing grass-based cattle feeds with legume leaves and its effects on manure quality and value as a soil improver for an Anthropic Ferralsol in Rwanda

“…In addition to increasing N, P and K, manure application increased Ca 2 and Mg 2 concentrations at the planting stations. This increase in base cations indicates that manure plays a substantial role in provision of these nutrients, either by direct decomposition of manure and/or by influencing their availability through provision of exchange sites in soil organic matter (Mulia et al, 2019).…”

A one health exploration of the reasons for low cocoa productivity in West Sulawesi

“…Mixed farming, such as cocoa/goat systems, has particular benefits as local resources available on the farm can be used and recycled. Declining soil organic matter content is a critical problem on cocoa farms [16] that can be redressed with manure from livestock, while legume shade and groundcover plants on the farm can supply feed. Animal products, including eggs and meat from chickens and ducks, are valuable supplements to the diet [14,20,44,45].…”

“…Table 1 is a research framework showing the inter-relatedness of the health of soil and crops, humans, livestock and the environment [14,15] as well as economic status. Reduced soil organic matter on farms [16] impacts nutrient availability and plant health, which in turn affects animal and human nutrition. Weakened plants, including tree crops, due to poor soil nutrition or aging, increase vulnerability to pest/diseases and leads to crop losses [17,18].…”

Variation in Indonesian cocoa farm productivity in relation to management, environmental and edaphic factors

“…Nevertheless, the impact of fertilisers will be greater and more cost-effective if the quantity and type is matched to local soil conditions. Where soils are depleted, inorganic fertiliser applied alone may have little or no impact (as demonstrated by Mulia et al (2019) on marginal acidic soils in North Luwu, South Sulawesi). Optimisation of the use of inorganic fertiliser is particularly important given the cost restraints cited by 43 and 35% of farmers in 2015 and 2016, respectively.…”

“…In recent years there has been a national decline in total cocoa production in Indonesia (ICCO, 2019). This may be due, in part, to farmers switching to less labour-intensive crops, such as oil palm (Mulia et al, 2019). Furthermore, factors such as pests and diseases and soil fertility decline can put downward pressure on yields (Ruf and Yoddang, 2001), the key pests and diseases being blackpod (causal agent: Phytophthora palmivora), vascular streak dieback (causal agent: Ceratobasidium theobromae), cocoa pod borer (Conopomorpha cramerella) and mosquito bug (Helopeltis theobromae).…”