Optimizing soil nitrogen balance in a potato cropping system through legume intercropping
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Date
2020
Authors
Nyawade, Shadrack O.
Karanja, Nancy N.
Gachene, Charles K. K.
Gitari, Harun I.
Schulte-Geldermann, Elmar
Parker, Monica
Journal Title
Journal ISSN
Volume Title
Publisher
Springer
Abstract
Negative nitrogen balance represents a
major factor causing low potato yield in potato
growing areas of Kenya while its excessive surplus
poses a significant environmental concern. In order to
synchronize this tradeoff, a field trial integrating
potato (Solanum tuberosum L.) with lima bean
(Phaseolus lunatus L.) and dolichos (Lablab purpureus
L.) in intercropping system was conducted in
the upper midland [1552 m above sea level (masl),
lower highland (1894 masl) and upper highland
(2552 masl)] agro-ecological zones of Kenya. Nitrogen
gains from mineralization, fertilization, biological
fixation, and outputs from biomass accumulation,
leaching, volatilization and soil erosion were quantified
using standard procedures. Soil N balance ranged
from - 10.7 to - 18.1 kg N ha-1 for sole potato, 4.1
to 6.6 kg N ha-1 for intercropping and 2.9 to
22.3 kg N ha-1 for sole legumes. The intermediate
range of polyphenol and lignin contents in intercropping
enhanced N mineralization with peak N release of
8 to 9 kg N ha-1 matching with peak N uptake by
potato (19.9 to 31.2 kg N ha-1). Nitrate was leached
below the active root zone in sole potato cropping (4.2
to 46.6 kg N ha-1), a process that was diverged by the
deep root systems of legume intercrops. These results
suggest that legume intercropping can provide a
means of balancing the nitrogen retained in the
biomass and soil, thus offering a mechanism for
optimizing the soil N balance in smallholder potato
farming systems.
Description
Research Article
Keywords
Legume intercropping, Nitrogen balance, Nitrogen mineralization, Nitrogen uptake