Does long-term low-rate organic and inorganic nitrogen management guarantee maize yield under semi-arid conditions of eastern Kenya?
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Date
2014-07
Authors
Kisaka, M. Oscar
Mucheru-Muna, M.
Ngetich, K. F.
Mugwe, J.
Mugendi, D.
Mairura, F.
Journal Title
Journal ISSN
Volume Title
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Abstract
Drier parts of Embu County endure high atmospheric heat, prolonged dry spells, declining
soil fertility and erratic rainfall. Integrated soil fertility management (ISFM) technologies
have been developed, and tested, with standardized application procedures and rates aimed
at optimizing overall yield productivity. Despite their significant impacts, high variability in
local soils and climate contributes to large variations and inconsistence in research results
among replications of the expensive and limited (time/site/scenarios) experimental treatments.
This occasions poor comparability of results within-and-without different agro-ecological
zones (AEZs) due to the complex non-linear soil-climate-crop relations. 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, parameterized and calibrated
based on a rain-fed randomized complete block trial (2010-to-2013) at a research station in
Machang’a, Embu County; and the long-term N management in maize production. The
trials combined three and two level amendments each as follows; inorganic fertilizers (30 kg
N ha-1, 60 kg N ha-1 and 90 kg N ha-1), goat manure, Lantana camara, Tithonia diversifolia
(each at 30 kg N ha-1 and 60 kg N ha-1), Mucuna pruriens ( N depended on residue
harvested; in a mirror rotation with maize) and control (TSP 60 kg ha-1); replicated three
times. Half rate (30 kg N ha-1) applications were complimented by half rate inorganic fertilizer
application. Model validation was based on goodness-of-fit between observed and simulated
parameters derived from residual-errors statistics; root mean square error (RMSE), square
of the correlation coefficient (R2), and model efficiency (EF). APSIM simulations adequately
predicted observed maize crop-growth (Leaf Area Index; LAI, Grain yield, and biomass).
Grain prediction across the treatments was good (R2=0.87 and EF>0.9) but biomass was
slightly under-predicted (R2=67 and EF=0.87). Long-term (26 cropping seasons) simulations
showed that moderate and low cost application of N (40 kg N ha”1 from combined manure
and mineral fertilizer) improved both long-term average and the minimum guaranteed grain
yield (2.5 Mg ha-1) and thus recommended for smallholder farmers especially in dry areas.
These findings should be considered in conditions where P is added proportionally to N (P/
N in the range of 20 to 30%).
Description
Fourth RUFORUM Biennial Regional Conference 21 - 25 July 2014, Maputo, Mozambique, pg487 - 493
Keywords
Agro-ecological zones, Integrated soil fertility management