Maize Yield Response to Green Manure Application from Selected Shrubs and Tree Species in Western Kenya: A Preliminary Assessment

Three field experiments were carried out to test the response of maize grain yield to the application of green manure from five species of shrubs and one tree species in four sites in Western Kenya. The species tested were Senna (=Cassia) spectabilis, Lantana camara, Tithonia diversifolia, Calliandra calothrysus, Psidium guajava (guava) and Grevillea robusta. At two of the experimental sites, groups of farmers tested the response of maize to the application of green manure from tithonia and lantana under their own field conditions and management. The rate of green manure application ranged from 5 to 20 t/ha on dry matter basis. The control plot that was adopted in this experiment was a continously cropped plot which did not receive green manure. Tithonia and lantana green manure gave the highest maize grain yields (4–5 t/ha) when applied at the rate of 5 t/ha but there were no yield differences between treatments with the two species when the rate of application of green manure was increased to 10 and 20 t/ha. The residual effect from tithonia and lantana green manure was more pronounced than from treatments with phosphoric fertilisers. Farmers realised comparatively higher maize grain yields from the application of tithonia green manure than from lantana although most them did not apply the prescribed quantitites of the green manure. Tithonia was the more preferred manure spices by farmers.