Nitrogen Mineralization Potential (No) in Three Kenyan Soils: Andosls, Ferralsols and Luvisols
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Date
2018
Authors
Karuku, George N
Mochoge, Benson O
Journal Title
Journal ISSN
Volume Title
Publisher
Canadian Center of Science and Education
Abstract
Nitrogen mineralization potential is important so as to prevent over-fertilization that could lead to groundwater
contamination or under-fertilization that could lead to poor nutrient provision by crops leading to low yields.
Three soil types were selected on the basis of groups, agro-ecological zone, organic matter content and land use.
The soil samples were taken from the 0-15 and 15-30 cm depth. The samples were placed in incubation bags,
water added to field capacity, sealed and incubated in laboratory at room temperature. The bags were opened at
intervals of two weeks and soil sub-samples taken for analysis of mineral N for a period of 17 weeks. The
calculated mineralizable N was 138.8 μg N and 116.4 μg N/g for Gituamba andosols, 46.0 μg N and 46.4 μg N/g
for Kitale ferralsol and 260.1 μg N and 197.3 μg N/g soil for Katumani luvisols in the 0-15 and 15-30 cm depth,
respectively. These calculated values compared well with the actual cumulative mineralizable N for Gituamba
andosols at 127 μg N and 74.1 μg N/g, for Kitale ferralsols at 48.0 μg N and 64.1 μg N/g and for Katumani 80.6
μg N and 47.7 μg N/g soil in the 0-15 and 15-30 cm depth, respectively. The time taken for 50% of potentially
mineralizable N to be mineralized (t½) ranged from 6.3 weeks for Katumani luvisols 15-30 cm to 30.1 weeks for
Kitale ferralsols 0-15 cm soil depths. The soils with highest rate constant (k) had the least. For example, 15-30
cm depth of Katumani luvisols with of 6.3 weeks had the highest k of 0.112 week-1 compared with Kitale
ferralsols 0-15 cm depth with t½ of 30.1 weeks and the lowest k of 0.023 week-1. The observed data indicates
that 50% of N would be mineralized in all the soil types with the exception of Kitale ferralsols (0-15 cm depth)
within the growing period of the crops which is approximately 20 weeks
Description
Article
Keywords
nitrogen mineralization potential (No), mineralization rate constant (k), t½
Citation
Karuku, G., & Mochoge, B. O. (2018). Nitrogen mineralization potential (No) in three Kenyan soils: Andosls, Ferralsols and Luvisols. Journal of Agricultural Science, 10(4), 69.