Standardisation of organic materials as amendment for soil and soilless media in urban horticultural production systems
A survey was carried out in Tamale and Kumasi among horticultural practitioners from March 2012 to June 2012 and subsequently, experiments were carried out from June 2012 to June 2015 to select and standardise organic materials as media for urban horticulture. Following the survey, i) single species sawdust (SS), ii) mixed species sawdust (MS) and ii) Rice husk (RH) were each co-composted with poultry manure in 2:1, 3:1 and 4:1 volumetric ratios of feedstock to poultry manure. This resulted in nine compost-types (formulations) being 2SS, 3SS, 4SS, 2MS, 3MS, 4MS, 2RH, 3RH and 4RH. Experiments were set-up in greenhouse and in the field to determine the rate of application of compost and biochar as amendment in soil and soilless media for vegetables and ornamentals. Treatments included compost-type:topsoil and compost-type:biochar mixes in soil experiments as well as compost-type:biochar mixes as soilless media. Competely Randomised Design was used for greenhouse experiments and Randomised Complete Block Design for the field experiment. The 2SS compost matured earliest (8 weeks) with Carbon: Nitrogen ratio (C:N) of 15 and highest nitrogen level of 2.46 %. The 1-part 2RH compost + 3 parts topsoil as well as 1 part of 2SS compost + 3 parts topsoil were the best for vegetables. The 2 parts of 2MS + 3 parts topsoil was the best for ornamentals. Sawdust compost (at 10 t/ha) + sawdust biochar (at 5 t/ha) was the best compost biochar mix for field production of vegetables. The 1 part of 2RH compost + 2 parts rice husk was the best media for greenhouse zinnia production. The 2SS compost + SS biochar was best media for greenhouse production of vegetables. The present study has clearly demonstrated that common agro-industrial by-products which are currently causing environmental challenges to urban authorities can be developed into nutrient rich media suitable for horticultural production systems and greening of the urban landscape.
Thesis submitted to the Department of Horticulture, College of Agriculture & Natural Resources, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfillment of the requirements for the Doctor of Philosophy (Landscape Science & Ecology) degree, 2015