How nutrient rich are decaying cocoa pod husks? The kinetics of nutrient leaching

Abstract

Aim Recycling of cocoa pod husks has potential to contribute to mineral nutrition of cocoa. Yet little is known of the nutrient content and nutrient release patterns from the husks. The potassium (K) rich husks are usually left in heaps in cocoa plantations in Africa. We aimed to understand and quantify release patterns of K and other nutrients from husks under varying rainfall regimes and assessed the effects of partial decomposition and inundation on nutrient leaching rates. Methods We incubated chunks of cocoa pod husks to assess decomposition rates and we measured nutrient leaching rates from two sets of husk chunks: one set was placed in tubes that were submitted to simulated scheduled rainfall events while the second set was continuously inundated in beakers. Results Decomposition of husks followed a second-order exponential curve (k: 0.09 day−1; ageing constant: 0.43). Nutrient losses recorded within 25 days were larger and more variable for K (33%) than for other macronutrients released in this order: Mg > Ca ≈ P > N (less than 15%). Potassium leaching was mainly driven by rainfall frequency (P < 0.05) and reinforced by intense rainfall, especially at lower frequency. Under water-saturated conditions, 11% of K was leached out within 48 h from fresh husks compared with 92% from partially decayed husks. Conclusion Some initial decomposition of cocoa pod husks is required to expose K to intense leaching. As decomposition progresses, abundant K losses are to be expected under frequent and/or intense rainfall events.

Soil Physiochemical Properties and Cucumber Productivity Assessment under Organic Fertilization

“…The soil physicochemical properties showed a signi cant increase in this study which is a re ection of the application of organic manures of poultry droppings, cow dung, and cocoa pod husk (Dang et al, 2021;Hougni et al, 2021). Kumba, Cameroon, is dominated mainly by sandy soils with a fragile structure, little capacity for retaining water, high permeability, and sensitivity (Huang and Hartemink, 2020); thus, soil amendment with organic manures is imperative for enhanced soil fertility and crop production (Ngosong et al, 2020).…”

“…The particle size of the soil done by utilizing the pipette method and sodium hexametaphosphate as the dispersion agent (Kalra et al, 1991). The potentiometric method was used for soil pH in both water (H 2 O) and 1M Potassium chloride (KCl) solutions after twenty-four (24) hours in suspension (solid/liquid = 1/2.5 w/v). A neutral solution of ammonium acetate was used to extract exchangeable bases.…”

“…Cow dung, on the one hand, provides essential plant nutrients and is e cient in fungi and bacterial disease reduction as it is effective in limiting plant pathogenic fungi like Fusarium solani and Fusarium oxysporum mycelial growth (Ozlu et al, 2019;Dang et al, 2021). Cocoa pod husk obtained after cocoa beans processing is a rich source of macro and micronutrients and modulates soil pH status, but it is often abandoned as waste (Fidelis and Rajashekhar Rao, 2018; Hougni et al, 2021). In general, organic manures are recognized for their ability to increase soil qualities including soil structure, Cation Exchange Capacity (CEC), and water holding capacity, as well as for slowing down the release of nutrients across the crop production cycle and activating microbial biomass.…”