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 intra-seasonal dry spells that result in low

prodty and crp failure (Manyatsi et al., 2011). 2

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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.

 

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)

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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T, S = (p < 0.001)

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T = (p = 0.057)

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CONCLUSIONSThese 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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