.. rr ,) \ A S'roDY OF AILEY LEUCAENA ~ (( CHOPPING MAIZE AND GREEN GRAM WITH (LAM) DE WIT AT MI'WAPA, COAST PROVINCE, KENYA BY A Thesis submitted in partial fulfilment of the requirements for the degree of MASTER OF SCIENCE IN AGRONa1Y r at the UNIVERSITY OF NAIROBI Faculty of Agriculture 1988 UNlVBRSITY OF NAIRa lFlRARY (xiii) ABSTRACT Crop yields in the Kenya Coastal lowlands are low because of poor soil fertility and high weed infestation. The sandy soils (92% in are all major nutrients N,P,K, highly sand), leachable deficient and" fertilizer application is necessary for good crop yields. Green' leaf Manure established in a (GlM) from split-plot Incorporat.ed to Leucaena systematic made design with hedgerows (alleys) 5-replications were boost soil fertility, by cutting them down to O.5m from the ground level 2 weeks before maize crop were leucocephala during the cropping planting. season Two additional cuttings for additional GUM and to minimize Leucaena shading on the crop. Assessment of crop yields carried a period of four years (1982-1985). out the usual over trend of continuous cropping The system was continuous cropping soil was even pruning during which and monitoring fertility reversed able 'to years, crops of decline with increase soil that fertility trends was It was observed that normally results with the use of Leucaena alley farming. maize yield by 38% after four except for the period of tree establishment and were significantly reduced due to excessive shade effect. Soil tests also showed a gradual increase phosphorus, potassium, calcium, magnesium and pH This was due to the high organic in soil over the N-additions , up Leucaena GlM, nutrients release from tree root death and finally, the tree nutrients savings density/ha, the from uptake by weeds. higher the concentration including an increase in soil pH. % to organic carbon, control plot's. 283Kg N/ha from decomposition, and In general, the higher of soil nutrients (xiv) Significant weed cqntrol of upto 90% was achieved due to the fallow effect preceding the alley cropping. grass weeds were reduced Besides, most of the difficult to in favour of the easier to control broad-leaved, non-grass weeds. The Financial returns and savings fuelwood GLM the system and to control from were the also sale and remarkably use of high. cuttings during one cropping season yielded 28.3 t/ha of fresh GLM.