Using APSIM-model as a decision-support-tool for long-term integrated-nitrogen-management and maize productivity under semi-arid conditions in Kenya
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Date
2015
Authors
Mucheru-Muna, M.
Ngetich, K. F.
Mugwe, J. N.
Mugendi, D.N.
Mairura, F.
Muriuki, J.
Journal Title
Journal ISSN
Volume Title
Publisher
Cambridge University Press
Abstract
There is continued decline in per capita agricultural productivity in the drier parts of Kenya’s central
highlands. The declines have been linked to low and declining soil fertility, soil water, high atmospheric
heat, prolonged dry-spells and erratic rainfall. Integrated soil fertility management (ISFM) technologies
have been developed and tested in the region. Despite their significant impacts, high variability in local
soils and climate contributes to large variations and inconsistency in research results among replications.
Experimentation is expensive and limited to a few years, sites and scenarios. Crop-growth simulation models
suitably complement experimental research, to support decision making regarding soil fertility and water
management. This study evaluated the performance of the Agricultural Production Systems Simulator
(APSIM) model. APSIM was parameterized and calibrated based on a rain-fed randomized complete
block trial (2009–2012) at a research station in Machang’a, Embu County. The study further reported
on long-term effects of integrated Nitrogen (N) management from organic residues (goat manure, Lantana
camara, Tithonia diversifolia and Mucuna pruriens) and their combination with mineral fertilizers in maize
production. The model adequately reproduced the observed trends of maize leaf area index (LAI) and
yield response to the test N amendments. Long-term simulations showed that application of 0, 20 and 40 Kg
N ha−1 had low inter-seasonal variations (CV = 18–33%) in yields. High yield variability (CV > 56%) was
observed in the application of 60 and 80 Kg N ha−1. Application of 40 Kg N ha−1 by combining mineral
fertilizer and manure showed 80% chance of harvesting more than 2.5 Mg ha−1 of maize grain yield.
Maize stover mulching at 5 and 6 Mg ha−1 with the same N application increased long-term guaranteed
grain harvests to 3.5 Mg ha−1. This is when complemented with 90 Kg P ha−1. This integrated N and
soil water management is thus recommended. For subsistence farming, low-cost recommendations are
geared towards some ‘guaranteed’ yield stability each cropping season. This recommendation underpins
low-cost technologies that reduce production risks among small-holder farmers who faced with intermittent
financial problems, to improve food security. However, there is need to evaluate and verify that there is a
positive balance of primary nutrients such as N, P and K in such a fertility and water management option.
Its effects on C:N levels ought to be evaluated as well.
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Citation
Expl Agric.: page 1 of 21 C Cambridge University Press 2015