Authors:
Vincent Rabach ,
Jonathan Muriuki, ,Oscar Masika,
James Koske,
Chester Kalinda |
Abstract:
Declines in soil fertility and water, prolonged dry-spells/droughts and erratic climatic patterns in
general continue to undermine optimal agricultural productivity in Sub-Saharan Africa (SSA).
Drier parts of Eastern Kenya already endure low/declining soil fertility, low soil water content,
increased temperatures/atmospheric heat, and unpredictable rainfall and drought patterns. These
have occasioned continued declines in smallholder farm productivity (below 1 Mg ha-1 against a
potential of 6-8 Mg ha-1
) and resiliency. Optimizing on on-farm soil water and fertility
management through conservation agriculture (CA) technologies such as sustained soil
cover/residue retention, micro-dosing and minimum tillage, integrated with selected tree species
(for soil fertility enhancement, fodder, firewood) may hold in upgrading and developing
resiliency towards extreme climatic risks among smallholder farming systems. Redressing the
problem of increased food insecurity and productivity challenges requires a farming system that
maximizes on yield productivity per unit water/nutrient and/or land. This study evaluated the
best integration of Gliricidia sepium and Calliandra calothyrsus in a maize inter-cropping
system under conservation agriculture (CA) among smallholder farmers in dryland Eastern
Kenya, using completely randomized block design trials, where CA (minimum tillage) and
conventional agricultural (COA) systems were evaluated. Gliricidia sepium and Calliandra
calothyrsus were integrated at inter-row spacings of 4.5m, 3.0m and 1.5m; and 1m intra-row in
each system in plots of 12 by 12 m, set up at the Agricultural Research Station (ATC) in
Machakos, Kenya. Yield data was analyzed with mixed model of analysis of variance, treating tree species, inter/intra row tree spacing and CA/COA as fixed effects, while maize, legume, tree
yield and replication were treated as random effects. Accounting for heteroscedasticity utilized
modeling the covariance structure with power-of-the-mean using Genstat 14. Standard error of
difference of means (SED) test (p < 0.05) was used to evaluate how significant treatments
differed from each other. Results showed that Calliandra spaced at 3 or 4.5 m yielded
significantly (p= 0.003 and 0.01) higher maize yield when compared to spacing Calliandra at
1.5. Yields (Grain=5.31 and stover=5.66 Mg ha-1
) in Gliricidia spaced at 4.5 m were
significantly (p=0.01) higher compared to yield in any other treatments tested. No significant
(p=0.136) differences occurred in maize yields under CA or COA as sole and on integration with
tree species. Yields at researcher managed trials were more than those at on farm trials, whereas
in both, productivity of biomass; growth of canopy; heights and tree circumference were
enhanced in CA than COA. |
