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Partnerships for enhanced engagement in research (PEER) SCIENCE
Cycle 3 (2014 Deadline)

Biochar and compost from cocoa pod husk: opportunities for crop fertilization and suppression of black pod disease

PI: Njukeng Nkengafac (, Institute of Agricultural Research for Development, Cameroon 
U.S. Partner: Bin Gao, University of Florida
Project Dates: September 2014 to October 2016

Soil depletion, pests, and diseases have been identified as some of the main causes of low production in smallholder farms, which depend on agriculture to make a living and feed their families. Cocoa (Theobroma cacao), 80 percent of which is cultivated by smallholders, is an export crop for many countries in Africa, and black pod disease caused by Phytophthora spp. is a major constraint to its production. While cocoa pod husk has been identified as a major source of inoculum of P. megakarya and is often left in farmers' fields as waste, it can be used for crop fertilization in the form of compost or biochar, thus improving soil fertility, promoting plant growth and resistance to biotic stresses, and, in turn, helping mitigate climate change.

This research study focuses on cocoa pod husk conversion into compost and biochar and aims to characterize the converted product, evaluate its effects on soil physicochemical properties and black pod disease suppression, and assess crop growth and yield. Farmers and students will receive training on composting and biochar preparation and application. Cocoa pod husk will be composted, and some of the husks will be dried and burned in limited oxygen in a kiln to produce biochar. Compost and biochar from cocoa pod husk will be incorporated into soils at different rates, and the soil physicochemical properties, as well as the black pod disease suppression, will be evaluated. The mode of action by which compost and biochar suppress cocoa pod disease will be determined by investigating the microbial basis of disease suppression and induced resistance mechanism. The growth of the plants in these amended soils will also be evaluated. At the end of the study, researchers anticipate to obtain information on how to control P. megakarya and how to improve soil properties for enhanced cocoa production.

Biochar and compost can be used as an alternative to control black pod disease and improve cocoa yields in smallholder farms while reducing farmers' spending on chemicals for black pod disease treatment, as well as their time spent to take care of the farms. Enhanced crop yield would thus improve farmers' income, consequently reducing extreme poverty among smallholder farmers. Converting cocoa pod husk into biochar and compost is expected to provide an affordable source of environmentally friendly fertilizer that can be used for enhanced production of crops and vegetables without depleting the soil, thus enhancing food security and reducing hunger and malnutrition.

3-12 Creating Compost3-12 Lab Equipment Installation
Project team members create compost for experimentation (photo courtesy of Dr. Nkengafac).The team installs and calibrates lab equipment (photo courtesy of Dr. Nkengafac).

Summary of Recent Activities

Dr. Nkengafac's project on Biochar has come to an end. This is a summary of the activities and results of the project.

Cost manure and biochar were produced from cocoa pod husk and the mature compost was dried and preserved for usage. Samples for the compost and biochar were analyzed and found to be very rich in potassium and nitrogen. The objective of the study on the microbial communities was to determine microbial populations associated with disease suppression in compost. The results this study showed that; fluorescent pseudomonads were not present in the compost. Total heterotrophic bacteria and actinomycetes dominated in the compost. Fungi were present in lower density.
The objective of studying the invitro antagonistic effects of biochar and compost on P. megakarya was to evaluate the effect of compost and biochar on mycelial growth of P. megakarya and detect possible suppressive effects (microbes, lethal effect of chemical component). The compost water extract consistently reduced the growth of P. megakarya compared to the control and the water extract from biochar. Autoclaving compost resulted in loss in growth suppressiveness.

Using the compost and biochar, some greenhouse studies were carried out. These greenhouse experiments were carried out in order to determine the influence of compost and biochar on growth of cocoa plantlets, induced resistance against P. megakarya using detached leaf assay, and microbial populations and activities associated with disease suppression in the substrates. The results showed that compost and biochar induced some resistance against P. megakarya. Biochar and manure were used to germinate some traditional African Leafy vegetable seeds as well as to grow the seedlings. These vegetables were; okra, jute mallow, night shade and Amaranthus. The compost and manure were used in varying concentrations. Results showed that mixing the soil media with biochar or compost manure improved seed germination compared to the control. The seedlings were latter transplanted into beds with different levels of biochar, compost and inorganic fertilizer applications. Results from this study showed some improvement in marketable vegetable production with supplementation.

Famers were sensitized on the use of cocoa pod husk under the main theme “management of cocoa pod husk for soil fertility and disease suppression”. Lectures were on conversion of cocoa pod husk to compost and biochar for soil fertility and disease suppression. A questionnaire was administered to evaluate the knowledge of cocoa famers on soil nutrient, pests and disease management. Preliminary analysis of the questionnaire data showed that farmers’ knowledge on soil nutrient pest and disease management is still very limited. After the sensitization talk, training on compost manure preparation from cocoa pod husk was carried out in the four chosen sites. This was followed by several follow up visits on the composting processes that were initiated at different locations. Turning of the compost and eventual drying and storage were done.

Training on biochar preparation was carried out at the different locations and land was prepared for the planting of maize in the experimental plots. Soil samples from the different fields were collected and analysed in the laboratory. These plots were pegged and planted. The composting processes that were initiated at different locations were completed and the compost and biochar prepared were used for planting maize. These organic amendments were applied two weeks before
planting of the maize. Cleaning of the maize field was done, growth and yield parameters were collected. A student from the higher teachers training college was involved in the planting and monitoring of one of the maize experimental fields Yoke- Muyuka. The maize has been harvested and yields for biochar and compost manure plots found to be comparable with those of inorganic fertilizer.

Martha Mounongo a student being supervised by the PI defended her Masters Degree thesis as well as Longue Morel who was being supervised by the co PI. Nkenganyi Felix, a student from the higher technical teachers training college is currently preparing his thesis. A draft article on the preparation and characterization of compost and biochar was prepared. A focused group discussion showed that many farmers were interested in using cocoa pod husk for biochar and compost manure production.They found it as a cheap source of fertilizer for their farms. Some of the farmers are already using these organic fertilizers in their farms. In fact during this group discussion, they visited a maize farm planted by some participating farmers using compost manure from cocoa pod husk.
However, they requested that a follow up from the trainer is needed to make sure that they are doing the right thing in the field.In most cases, they abandon the initiative. Secondly, they raised the issue of more training and sensitisation to other farmers. Most farmers are reluctant to use a technology they don`t master so continuous training will help them to master their skills. This is very important for for those who did not join the training at the beginning.

Farmers are practicing composting and/or biochar production in their farms and many more are willing to learn the techniques of producing these organic materials.

Cocoa pod husk is often left in farmers` fields as waste. Converting this material to biochar and compost for soil amendment has multiple benefits. Biochar and compost are evaluated globally as a means to improve soil fertility, promote plant growth and resistance to biotic stresses, and to mitigate climate change. Therefore, biochar and compost are alternative to control the black pod disease and cocoa yields in small holder farmers. This will result in reduced spending in buying chemicals for the treatment of the disease as well as time spent to take care of the farms. This will leave the farmers with more time to indulge in other income generating activities that will improve their standard of living. The higher crop yield will improve farmers` income thus reducing extreme poverty among small holder farmers.

Converting cocoa pod husk into biochar and compost will provide a cheap source of fertilizer to improve food security and reduce hunger and malnutrition. Using these organic fertilizers will help the farmers to produce more without depleting their soils. During this project many people were trained ranging from farmers to students. This important aspect of the project of capacity building is a powerful tool for development.

PEER Cycle 3 Grant Recipients