Nitrogen Fertilizer Equivalency Values for Different Organic Materials Based on Maize Performance at Kabete, Kenya
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Date
2004
Authors
Mugendi, D.N.
Kung'u, J.B.
Kimetu, J.M.
Palm, C.A.
Mutuo, P.K.
Gachengo, C.N.
Nandwa, S.
Journal Title
Journal ISSN
Volume Title
Publisher
Academy Science Publishers
Abstract
Decline in crop yields has been a major problem facing small
holder farming in Kenya and the entire sub-Saharan region.
This is attributed mainly to the mining of macronutrients
due to cropping without external addition of adequate
nutrients. Inorganic fertilizers are expensive hence
unaffordable by most small holder farmers. Although
organic nutrient sources are available. information about
the right proportions of application is scanty.
An experiment was set up in 1999 at the National
Agricultural Research Laboratories (NARL)at Kabete, with
the overall objective of determining nitrogen fertilizer
equivalencies based on high quality organic inputs. The
specific objectives of the study included determination of
the nitrogen fertilizer equivalency values of Tithonia
diversifolia, Senna spectabilis and Calliandra ca/othyrsus
and the investigation of nitrogen use efficiency from
combined organic and inorganic inputs.
The experiment consisted of maize plots to which freshly
collected leaves of Tithonia diversifolia (tithonial, Senna
spectabilis (senna) and Calliandra calothyrsus (calliandra)
(all with % N >3) obtained from hedgerows grown ex situ
(biomass transfer from outside) and urea (inorganic nitrogen
source) were applied. Results obtained indicated that a
combination ofboth organic and inorganic nutrient sources
gave higher maize grain yield than when each is applied
separately, except for tithonia whose sole application gave
better grain yield than a combination of the same with
mineral fertilizer. Maizegrain yield production after organic
and inorganic application was in the order of tithonia >
tithonta-urea = calliandra+urea > urea> senna-urea >
calliandra > senna > control. The percentage N recovery
was highest in sole application of urea followed by a
combination ofboth urea and tithonia while sole application
of tithonia biomass had relatively lower percentage N
recoveries. In both seasons, the mineral Ncontent was high
in sole application of tithonia than in senna and calliandra
treatments. The three organic materials (senna, calliandra
and tithonia) gave fertilizer equivalency values of 68%, 72%
and 119% respectively.
Description
Book Chapter
Keywords
N fertilizer equivalency, mineral-N, N-recovery