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Carbon and
nitrogen mineralization from selected organic resources
available to smallholder farmers for soil fertility
improvement in Zimbabwe
J. Nyamangara1*,
F. Mtambanengwe1 and C. Musvoto2
1Department
of Soil Science and Agricultural Engineering, University of
Zimbabwe, P. O. Box MP167, Mount Pleasant, Harare, Zimbabwe.
2Institute
of Environmental Studies, University of Zimbabwe, P. O. Box
MP 167, Mount Pleasant, Harare, Zimbabwe.
*Corresponding author. E-mail:
jnyamangara@yahoo.co.uk, jnyamangara@agric.uz.ac.zw.
Accepted 1 August, 2009 |
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A study was conducted to assess the N release dynamics of
three organic resources widely used by smallholder farmers
in sub-Saharan Africa to improve soil fertility. Addition of
cattle manure, miombo and mango (Mangifera indica)
litter to soil increased (p < 0.05) CO2-C
evolution compared to unamended soil. Cumulative CO2-C
evolution in all the three organic amendments followed first
order kinetics (R2 = 0.89 - 0.99). Slight N
mineralization occurred when cattle manure was added to soil
and addition of manure in combination with mineral N had no
effect on the extent of N mineralization. Compared to
unamended soil, miombo litter induced net immobilization of
N for 60 days and thereafter net N mineralization occurred.
Both untreated and composted mango litter immobilized N (up
to 15 mg N kg-1) during the 77 day incubation. It
was concluded that all the three organic resources were poor
and inadequate sources of N for plant growth in the short
term and should therefore be supplemented with mineral N to
reduce N immobilization and consequent N deficiency in
plants. However the organic resources may improve the soil
physical environment and also contribute to soil organic
matter build up in the long term.
Key words:
Cattle manure, Mangifera indica, miombo litter, N
mineralization and immobilization |
