| dc.description.abstract | Crop yields in the Kenya Coastal lowlands are low because of poor soil
fertility and high weed infestation. The sandy soils (92% sand), deficient
in all major nutrients N,P,K, are highly leachable and" fertilizer
application is necessary for good crop yields.
Green' leaf Manure (GlM) from Leucaena leucocephala hedgerows (alleys)
established in a split-plot systematic design with 5-replications were
Incorporat.ed to boost soil fertility, by cutting them down to O.5m from the
ground level 2 weeks before maize crop planting. Two additional cuttings
were made during the cropping season for additional GUM and to minimize
Leucaena shading on the crop.
Assessment of crop yields and monitoring of soil fertility trends was
carried out over a period of four years (1982-1985). It was observed that
the usual trend of soil fertility decline that normally results with
continuous cropping was reversed with the use of Leucaena alley farming.
The system was even able 'to increase maize yield by 38% after four
continuous cropping years, except for the period of tree establishment and
pruning during which crops were significantly reduced due to excessive
shade effect.
Soil tests also showed a gradual increase in soil % organic carbon,
phosphorus, potassium, calcium, magnesium and pH over the control plot's.
This was due to the high organic N-additions , up to 283Kg N/ha from
Leucaena GlM, nutrients release from tree root death and decomposition, and
finally, nutrients savings from uptake by weeds. In general, the higher
the tree density/ha, the higher the concentration of soil nutrients
including an increase in soil pH.
Significant weed cqntrol of upto 90% was achieved due to the fallow effect
preceding the alley cropping. Besides, most of the difficult to control
grass weeds were reduced in favour of the easier to control broad-leaved,
non-grass weeds.
The Financial returns and savings from the sale and use of
fuelwood and GLM to the system were also remarkably high.
cuttings during one cropping season yielded 28.3 t/ha of fresh GLM. | en |
