Ammonia volatilization following urea application at maize fields in the East African highlands with different soil properties

Ammonia volatilization following urea application at maize fields in the East African highlands... Use of nitrogen (N) fertilizer is underway to increase in Sub-Saharan Africa (SSA). The effect of increasing N rates on ammonia (NH3) volatilization—a main pathway of applied-N loss in cropping systems—has not been evaluated in this region. In two soils (Alfisols, ALF; and Andisols, AND) with maize crop in the East African highlands, we measured NH3 volatilization following urea broadcast at six rates (0–150 kg N ha−1) for 17 days, using a semi-open static chamber method. Immediate irrigation and urea deep placement were tested as mitigation treatments. The underlying mechanism was assessed by monitoring soil pH and mineral N (NH4 + and NO3 −) concentrations. More cumulative NH3-N was volatilized in ALF than in AND at the same urea-N rate. Generally, higher urea-N rates increased proportional NH3-N loss (percent of applied N loss as NH3-N). Based on well-fitted sigmoid models, simple surface urea application is not recommended for ALF, while up to 60 kg N ha−1 could be adopted for AND soils. The susceptibility of ALF to NH3 loss mainly resulted from its low pH buffering capacity, low cation exchange capacity, and high urease activity. Both mitigation treatments were effective. The inhibited rise of soil pH but not NH4 + concentration was the main reason for the mitigated NH3-N losses, although nitrification in the irrigation treatment might also have contributed. Our results showed that in acidic soils common to SSA croplands, proportional NH3-N loss can be substantial even at a low urea-N rate; and that the design of mitigation treatments should consider the soil’s inherent capacity to buffer NH3 loss. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Biology and Fertility of Soils Springer Journals

Ammonia volatilization following urea application at maize fields in the East African highlands with different soil properties

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Publisher
Springer Berlin Heidelberg
Copyright
Copyright © 2018 by Springer-Verlag GmbH Germany, part of Springer Nature
Subject
Life Sciences; Agriculture; Soil Science & Conservation
ISSN
0178-2762
eISSN
1432-0789
D.O.I.
10.1007/s00374-018-1270-0
Publisher site
See Article on Publisher Site

Abstract

Use of nitrogen (N) fertilizer is underway to increase in Sub-Saharan Africa (SSA). The effect of increasing N rates on ammonia (NH3) volatilization—a main pathway of applied-N loss in cropping systems—has not been evaluated in this region. In two soils (Alfisols, ALF; and Andisols, AND) with maize crop in the East African highlands, we measured NH3 volatilization following urea broadcast at six rates (0–150 kg N ha−1) for 17 days, using a semi-open static chamber method. Immediate irrigation and urea deep placement were tested as mitigation treatments. The underlying mechanism was assessed by monitoring soil pH and mineral N (NH4 + and NO3 −) concentrations. More cumulative NH3-N was volatilized in ALF than in AND at the same urea-N rate. Generally, higher urea-N rates increased proportional NH3-N loss (percent of applied N loss as NH3-N). Based on well-fitted sigmoid models, simple surface urea application is not recommended for ALF, while up to 60 kg N ha−1 could be adopted for AND soils. The susceptibility of ALF to NH3 loss mainly resulted from its low pH buffering capacity, low cation exchange capacity, and high urease activity. Both mitigation treatments were effective. The inhibited rise of soil pH but not NH4 + concentration was the main reason for the mitigated NH3-N losses, although nitrification in the irrigation treatment might also have contributed. Our results showed that in acidic soils common to SSA croplands, proportional NH3-N loss can be substantial even at a low urea-N rate; and that the design of mitigation treatments should consider the soil’s inherent capacity to buffer NH3 loss.

Journal

Biology and Fertility of SoilsSpringer Journals

Published: Feb 28, 2018

References

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