Nitrogen mineralization in tropical soils amended with crop residues

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Date
2002-07-03
Authors
Abdelrahman, Mubarak
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Publisher
uofk
Abstract
Continuous incorporation of crop residues after harvest can contribute to restoring the health of the soil. A 12-week aerobic incubation study was carried out with the objective of determining N mineralization in five tropical soils and in soils amended with groundnut (Arachis hvpogaea) haulm and maize (Zea mays) stover. Plant materials (4 t ha-1) were mixed with the topsoil of five soil series, namely, Bungor sandy clay loam (Typic Paleudult), Munchong clay (Haplorthox), flengam sandy clay (Typic Paleudult), Selangor silty clay (Typic Aquept), and Serdang sandy clay loam (Typic Paleudult). Nitrogen mineralization rates of indigenous soil organic matter (SOM) were 0.024 mg N kg- 1, 0.051 mg N 0.064 mg N kg', 0.052 my N kg-1, and 0.042 mg N kg-1 week' for the five series, respectively. In these soil series, 9 mg N to 15 mg N kg-1 was potentially mineralizable. After 12 weeks of incubation, net N mineralization was observed only in the Bungor series (24 mg N kg-1 soil from the groundnut haulm and 13 mg N kg-1 from the maize stover). In the other soil series, immobilization was observed ranging from 6 mg N to 94 mg N kg-1 in soils amended with groundnut haulm and 15 my N to 105 mg N 1(g-' in soils amended with maize stover. The soil texture had little effect nn N mineralization in soils amended with crop residues. Generally, by the end of the incubation period, the soil pH values increased (P 0.05) from 0.26 to 1.44 due to amendments with plant residues.
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Keywords
Crop residues; N mineralization; Soil pH; Tropical soils
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