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Nitrogen rate impacts on tropical maize nitrogen use efficiency and soil nitrogen depletion in eastern and southern Africa

Authors
  • Pasley, Heather R.1
  • Camberato, James J.1
  • Cairns, Jill E.2
  • Zaman-Allah, Mainassara2
  • Das, Biswanath3
  • Vyn, Tony J.1
  • 1 Purdue University,
  • 2 International Maize and Wheat Improvement Centre (CIMMYT), Harare, Zimbabwe
  • 3 International Maize and Wheat Improvement Centre (CIMMYT), Nairobi, Kenya
Type
Published Article
Journal
Nutrient Cycling in Agroecosystems
Publisher
Springer Netherlands
Publication Date
Feb 13, 2020
Volume
116
Issue
3
Pages
397–408
Identifiers
DOI: 10.1007/s10705-020-10049-x
PMID: 32765186
PMCID: PMC7380447
Source
PubMed Central
Keywords
License
Unknown

Abstract

Sub-Saharan Africa is facing food security challenges due, in part, to decades of soil nitrogen (N) depletion. Applying N fertilizer could increase crop yields and replenish soil N pools. From 2010 to 2015, field experiments conducted in Embu and Kiboko, Kenya and Harare, Zimbabwe investigated yield and N uptake response of six maize ( Zea mays L.) hybrids to four N fertilizer rates (0 to 160 kg N ha−1) in continuous maize production systems. The N recovery efficiency (NRE), cumulative N balance, and soil N content in the upper 0.9 m of soil following the final harvest were determined at each N rate. Plant and soil responses to N fertilizer applications did not differ amongst hybrids. Across locations and N rates, NRE ranged from 0.4 to 1.8 kg kg−1. Higher NRE values in Kiboko and Harare occurred at lower post-harvest soil inorganic N levels. The excessively high NRE value of 1.8 kg kg−1 at 40 kg N ha−1 in Harare suggested that maize hybrids deplete soil inorganic N most at low N rates. Still, negative cumulative N balances indicated that inorganic soil N depletion occurred at all N rates in Embu and Harare (up to − 193 and − 167 kg N ha−1, respectively) and at the 40 kg N ha−1 rate in Kiboko (− 72 kg N ha−1). Overall, maize N uptake exceeded fertilizer N applied and so, while yields increased, soil N pools were not replenished, especially at low total soil N levels (< 10,000 kg N ha−1 in top 0.9 m). Electronic supplementary material The online version of this article (10.1007/s10705-020-10049-x) contains supplementary material, which is available to authorized users.

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