Effect of conservation tillage on soil moisture and crop
yields in Mwala District, Kenya
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Introduction, Problem statement & Justification
 Conventional tillage (CT) – the mechanical soil manipulation; the
cultivation using ploughs, harrows or mechanical implements to
prepare the field for crop prodn (FAO, 2000).
 Causes soil compaction, affects soil phy properties, provokes
biological degradation......declined crp yields.
 CT in Kenya, involves hand hoes, ox drawn mould board ploughs,
tractor drawn disc ploughs and harrows tog with straw collection and
burning (Gachene and Kimaru, 2003).
 Conservn tillage (CA) practices e.g. tied ridging, subsoiling & ripping
hv the potential of soil moisture retention & mitigation of intraseasonal dry spells that result in low prodty and crp failure (Manyatsi et
al., 2011).
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 In Kenya, CA practices involve use of mulch, ripping and sub-soiling without
inverting soil (Gitonga et al., 2008).
 Although practiced by large-scale farmers esp in the Mt Kenya region, CA is
slowly being adopted by some small-scale farmers, and evaluating its
performance in these condns is presently a priority.
 Although CA is highly advocated, there is strong evidence that this kind of
tillage may not be good with soils prone to surface crusting and sealing, a
xstic of most of the soils in semi arid areas of Kenya (Unger et al., 1991, Mudjeci
et al., 2010).
 Therefore, the objective of this study was to assess the effect of conservation
tillage on soil water conservation and yields of maize and beans relative to
the conventional tillage in a semi arid region of Eastern Kenya.
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Materials and Methods
 Study area: Mbiuni Location, Mwala District, Kenya
 The mean annual rainfall for Mwala District is 596 mm
 Trials established during the long rains (LR) and short rains (SR) of
2012/13.
 6 tillage sys: Disc plough (MB), Disc plough and Harrowing (MBH),
Ox-ploughing (OX), Hand hoe and Tied Ridges (HTR), Hand hoe only
(H) and subsoiling – ripping (SR)
 3 cropping sys- sole maize (M), sole bean (B) and maize-bean
intercrop (M + B)
 Split-plot design with 4 reps.
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Data collection
 Soil moisture - at depths of 0 - 20 cm and 20 - 40 cm using the
gravimetric method (Okalebo et al., 2002).
 Test crops - dryland maize variety (DH 02) and beans (rose coco -
GLP 2)
 Final crop biomass and grain yields were det from plants harvested in
a 2 × 2 m at the centre of the plot.
 The data was subjected to ANOVA to evaluate the trt effects
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Locally manufactured Magoye ripper and subsoiler, which can fit onto the
same frame as the plough beam (Source: Kaumbutho and Kienzle, 2007)
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T = HTR > MBH > H > OX > MB (p = 0.019)
C = B > M > M+B (p = 0.891)
Time x T x C = (p = 0.005)
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T = OX > SR > MB > HTR > H > MBH (p = 0.158)
C = M > B > M+B ( p = 0.684)
Time x C = (p = 0.003)
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T = OX > SR > H > MB > MBH > HTR (p = 0.003)
C = B > M+B > M (p = 0.057)
Time x tillage (p < 0.001)
Time x C (p = 0.044)
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3 season moisture average indicate;
 Tillage trend is OX > H > MB > MBH > HTR > SR.
CT practices had the highest soil moisture content compared to
the CA methods (effect of pry and sec tillage implements used,
which improved porosity and WHC of the soil)
 Cropping sys - Sole bean > Sole maize > Intercrop (surface
cover - reduce evaporn, increasing infiltration, increased plant popl
density…higher moisture extraction.
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16.00
14.00
Maize grain and biomass yields as affected by
tillage
12.00
10.00
T = (p = 0.008)
S = (p < 0.001)
T, S = (p < 0.001)
8.00
6.00
4.00
2.00
0.00
LR 2012
SR 2012
LR 2013
LR 2012
Maize grain yield (Mg/ha)
SR 2012
LR 2013
Maize biomass yield (Mg/ha)
Tillage
H
HTR
MB
MBH
OX
SR
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Maize grain and biomass yields as affected by
cropping system
14.00
12.00
10.00
C = P < 0.001
8.00
6.00
4.00
2.00
0.00
LR 2012
SR 2012
LR 2013
Maize grain yield (Mg/ha)
Maize
LR 2012
SR 2012
LR 2013
Maize biomass yield (Mg/ha)
Maize + bean
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4.00
Bean grain and biomass yields as affected by tillage
T = (p = 0.046)
3.50
T = (p = 0.057)
3.00
2.50
2.00
1.50
1.00
0.50
0.00
LR 2012
SR 2012
LR 2012
Bean grain yield (Mg/ha)
SR 2012
Bean biomass yield (Mg/ha)
Tillage
H
HTR
MB
MBH
OX
SR
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3.50
Bean grain and biomass yield as affected by
cropping system
3.00
2.50
2.00
1.50
1.00
0.50
0.00
LR 2012
SR 2012
Bean grain yield (Mg/ha)
Bean
LR 2012
SR 2012
Bean biomass yield (Mg/ha)
Maize + bean
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CONCLUSIONS
 These results suggest that tillage methods and cropping
sys hv an influence on soil moisture conservn and crop
yields in the semi arid areas of Kenya.
 Inconsistencies in relative grain and biomass yields among
tillage treatments likely ass with the presence of soil
moisture at the time of tillage/planting, growing season and
prevailing climatic conditions
 Long term tillage expts are req!!! (diff locations, under
various environt’l and soil condns
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ACKNOWLEDGEMENT
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