(2003) Mugendi, D.N.; Karunditu, M. W.; Kung'u, J.B.; Vanlauwe, B.
Nitrogen (N) is the nutrient most limiting to crop production and effective management is inevitable to minimizeits losses through the many pathways. Nitrogen uptake and use efficiency as affected by soil organic matter status (SOM)in the soil-plant system was studied in three sites located at Eastern, Central and Western parts of Kenya using 15N tracertechnique. Among the three sites calliandra treatment recorded the highest total yields (core, stover, and grain) in themicroplot that was labelled first (L) (17,205 kg/ha). Maize grain yields were observed to be highest again at PM1 trial incalliandra treatment in the microplot labelled first (L) (6,337 kg/ha). Among the three sites Embu recorded the highestuptake and use efficiency in calliandra treatment in the microplot labelled second. The observation made in calliandracould be attributed to its low quality (slow decomposition and N release) hence its ability to build up SOM