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The decomposition of cocoa leaves and their effect on phosphorus dynamics in tropical soil
Author(s) -
OforiFrimpong K.,
Rowell D. L.
Publication year - 1999
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1046/j.1365-2389.1999.00208.x
Subject(s) - chemistry , phosphorus , soil water , litter , bicarbonate , incubation , decomposition , nutrient , plant litter , zoology , biomass (ecology) , agronomy , horticulture , biology , ecology , biochemistry , organic chemistry
Summary Higher‐yielding varieties of cocoa make heavier demands on phosphorus resources in soils and so it is important that the role of leaf litter in cycling P is understood. Fresh cocoa leaves and leaf litter were incubated moist with a soil inoculum for 80 days when between 16 and 33% of the mass was lost. Materials containing large amounts of P or incubated with added inorganic P initially decomposed more rapidly than those containing smaller amounts, indicating that decomposition was limited by lack of P. Fresh leaves had half of their P in an acid‐soluble (0.1 m H 2 SO 4 ) form, most of which was also water soluble, whereas in the litters about a third was acid‐soluble. During incubation, P‐rich materials showed an increase in the acid‐soluble fraction and a decrease in water‐soluble P. Litters with small concentrations of P simply lost P from the acid‐soluble into the non‐soluble organic fraction, and no water‐soluble P remained after 80 days. –A soil from a cocoa‐growing site fertilized with P contained almost four times as much biomass P as the non‐fertilized control (30 and 8 mg kg –1 soil, respectively), the amounts of bicarbonate‐extractable P being 32 and 4 mg kg –1 . Soils from these and one other cocoa‐growing site (8 mg kg –1 biomass P, 7 mg kg –1 bicarbonate‐extractable P) were incubated either alone, with cocoa litter, or with cocoa litter plus inorganic P. In the soil that had the small amount of NaHCO 3 ‐extractable P (4 mg kg –1 ) addition of litter caused the biomass P to increase from 8 to 16 mg kg –1 after 1 week's incubation, the increase being larger than the amount of P added in the litter, but in the other two soils biomass P was not increased. Addition of inorganic P had no effect on biomass P in any of the soils. –Decomposing litter may compete with the crop for P, but addition of fertilizer P may increase the rate of mineralization of organic P in the litter. Suitable management of fertilizer P should allow the rate of release of P from the litter to be adjusted to suit crop demands.