Effect of conservation tillage on soil moisture and crop yields in Mwala District, Kenya 1

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

3 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. 4

Data collection Soil moisture - at depths of cm and 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 5

6 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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8 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)

9 T = OX > SR > MB > HTR > H > MBH (p = 0.158) C = M > B > M+B ( p = 0.684) Time x C = (p = 0.003)

10 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. 11

12 T, S = (p < 0.001)

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14 T = (p = 0.057)

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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 16

17 ACKNOWLEDGEMENT

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