Papers by Abimfoluwa G . Olaleye
Soil Systems, 2020
This study investigated the speciation, transformation, and availability of P during indigenous v... more This study investigated the speciation, transformation, and availability of P during indigenous vegetable production by employing a combination of chemical and spectroscopic techniques. The study focused on sites in two ecozones of SSA, the dry savanna (lna, Republic of Benin) and rainforest (Ilesha, Nigeria). Both sites were cultivated with two indigenous vegetable species: local amaranth (Amaranthus cruentus (AC)) and African eggplant (Solanum macrocarpon (SM)). The soils were treated with 5 t/ha poultry manure and urea fertilizer at the rates of 0, 20, 40, 60, and 80 kg N/ha. Soil samples were collected before planting and after harvest. Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy was used to determine P speciation in these soils. Quantitative analysis showed that adsorbed and organic P were the two dominant P species in the manure amended dry savanna (DS) soils before planting and after harvest in soils cultivated with both AC and SM, with the addition of urea (40 kg N/ha) causing an increase in the organic P form in dry savanna soils cultivated with AC. Soils of the rainforest (RF) cultivated with AC initially had large amounts of apatite P in the manure amended soils prior to planting, which was transformed to adsorbed and organic P after harvest. Urea addition to the rainforest soils shifted the dominant P species from organic P to adsorbed and apatite P, which was likely to limit P availability. Soils cultivated with SM had similar proportions of both organic and adsorbed P forms, with 40 kg N/ha addition slightly increasing the proportion of adsorbed P.
Agronomy, 2020
Fertility management techniques being promoted in sub-Saharan Africa (SSA) seek to grow indigenou... more Fertility management techniques being promoted in sub-Saharan Africa (SSA) seek to grow indigenous vegetables economically and sustainably. This study was conducted in a phytotron chamber and compared yield, soil carbon (C) speciation and greenhouse gas (nitrous oxide (N2O) and carbon dioxide (CO2)) emissions from SSA soils of two ecoregions; the dry savanna (lna, Republic of Benin) and rainforest (Ife, Nigeria) cultivated with local amaranth (Amaranthus cruentus) under manure (5 t/ha) and/or urea (80 kg N/ha) fertilization. Vegetable yield ranged from 4331 kg/ha to 7900 kg/ha in the rainforest, RF, soils and 3165 kg/ha to 4821 kg/ha in the dry savanna, DS, soils. Yield in the urea treatment was slightly higher compared to the manure, and manure+urea treatment, but the difference was not statistically significant. Cumulative CO2 emissions over 21 days ranged from 497.06 to 579.47 g CO2-C/kg soil/day in the RF, and 322.96 to 624.97 g CO2-C/kg soil/day in the DS, while cumulative N2O emissions ranged from 60.53 to 220.86 mg N2O-N/kg soil/day in the RF, and 24.78 to 99.08 mg N2O-N/kg soil/day in the DS. In the RF samples, when compared to the use of urea alone, the combined use of manure and urea reduced N2O emissions but led to an increase in the DS samples. ATR-FTIR analysis showed that the combined use of manure and manure+urea increased the rate of microbial decomposition in the soils of the DS, but no such effect was observed in soils of the RF. We conclude that combining manure and urea fertilization has different effects on soils of the two ecoregions, and that RF farmers can reduce agricultural N2O emissions without compromising soil productivity and yield potential.
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Papers by Abimfoluwa G . Olaleye