On-farm fertilization experiment on small-scale cocoa farms in Côte d′Ivoire: Evaluation of poultry litter compost for sustainable yield and profitability

Abstract

Context

In Côte d’Ivoire, cocoa is primarily produced on small-scale monoculture plantations as the main source of income for much of the rural population. Fertilization of cocoa farms remains uncommon, and long-term production without fertilization contributes to soil degradation. The ongoing decrease in productivity on small-scale cocoa farms undermines producers’ livelihoods and aggravates poverty. Poultry litter compost from the emerging poultry industry bares potential as a sustainable alternative to mineral fertilizers, but its effectiveness and profitability for cocoa production remain unknown.

Objective

Our study aimed to compare productivity and profitability effects of mineral-, compost-, and mixed fertilizers on a representative sample of established small-scale, age-diverse cocoa fields.

Methods

Our randomized controlled on-farm experiment included 120 farmers’ cocoa fields in central Côte d’Ivoire to assess productivity and profitability of three fertilizer options over one production cycle: Organic- (composted poultry litter, 71 kg N ha⁻¹y⁻¹), mineral- (marketed NPK+, 15 kg N ha⁻¹y⁻¹), and 50:50 combined organic and mineral fertilization (43 kg N ha⁻¹y⁻¹). Experimental plots comprised three cocoa trees per treatment and trees were fertilized twice before trees’ main harvest yields were measured. We estimated bean dry weights, annual yields and financial incomes per hectare. Treatment differences in yield and market value per hectare were tested using linear mixed-effects models, and report value-to-cost ratio (VCR = additional cocoa market value divided by total fertilization cost) of treatments’ projected annual harvests. We predicted compost fertilization VCR under both low-end and high-end price scenarios to account for regional variation in commercialization of poultry litter sale and resulting price variance.

Results and conclusions

Organic fertilization led to the highest increase of main harvest productivity (+ 190 kg dryweight per ha (dw), 38 %) followed by mixed fertilization (+ 145 kg ha⁻¹ dw, 31 %) and mineral fertilization (+ 118 kg ha⁻¹ dw, 22 %). Organic fertilization showed a high positive return on investment (VCR_l = 3.08, CI = 1.94, 4.22) in the low cost scenario of USD 104 ha⁻¹ y⁻¹, but not when high costs were assumed (VCR_h = 0.94, CI = 0.59, 1.29, USD 342 ha⁻¹ y⁻¹). The value-to-cost ratio was below one for both the mixed (VCR_l = 0.88, CI = 0.47, 1.29, USD 290 and VCR_h = 0.62, CI = 0.33, 0.91, USD 409 ha⁻¹ y⁻¹) and the mineral fertilizer (VCR = 0.26, CI = 0.01, 0.51, USD 460 ha⁻¹ y⁻¹).

Significance

This study provides first experimental evidence of the effectiveness and profitability of organic fertilization with composted poultry litter in small-scale cocoa farming. Although fertilization is essential for improving productivity and income, the generally low VCR highlight the insufficient farm-gate cocoa prices, which hinder the profitable adoption of most tested fertilization strategies. Key policy recommendations include ensuring adequate farm-gate prices, providing targeted subsidies for input costs and logistics, and promoting extension services that encourage farmers to trial fertilizers on their fields. Further research, including long-term on-farm trials and qualitative studies on farmer perceived barriers to fertilizer adoption, is needed to inform effective policies that support the fertility and resilience of cocoa agroecosystems.