Expl Agric. (2007), volume 43, pp. 477–487 C  2007 Cambridge University Press doi:10.1017/S0014479707005315 Printed in the United Kingdom EFFECT OF PHOSPHATE FERTILIZER APPLICATION METHODS AND NITROGEN SOURCES ON MAIZE IN WESTERN KENYA: AN AGRONOMIC AND ECONOMIC EVALUATION By P. A. OPALA†, B. A. JAMA‡, C. O. OTHIENO¶ and J. R. OKALEBO¶ Bukura Agricultural College, P.O. Box 23, Bukura, Kenya, ‡International Center for Research in Agroforestry (ICRAF), P.O. Box 30677, Nairobi, Kenya, and ¶Moi University, Department of Soil Science, P.O. Box 1125 Eldoret, Kenya (Accepted 7 March 2007 ) SUMMARY Simultaneous deficiencies of nitrogen (N) and phosphorus (P) which limit crop production in western Kenya can be overcome through a combined application of organic and inorganic fertilizers. An experiment was conducted with maize (Zea mays) for two seasons to compare two methods of applying inorganic P fertilizer (broadcast versus spot) in a factorial combination with three N sources, i.e. farmyard manure (FYM), Tithonia diversifolia green manure (tithonia) and urea. Net financial benefits of the tested practices were computed using partial budgeting. Maize yield was not significantly affected by the P fertilizer application method in the first season, but the broadcast method was generally superior to spot application in the second season. The three N sources produced maize yields that were comparable in both seasons. FYM integrated with P fertilizer applied using the broadcast method, however, had the highest cumulative net benefit and was therefore the most economically attractive input combination. INTRODUCTION Phosphorus deficiency is a major constraint to crop production in many parts of western Kenya. Correction of P deficiency in these soils requires the application of mineral P fertilizers because most of the commonly available organic materials are low in P. However, P in most of the P fertilizers applied to these soils is rapidly fixed and this may impact negatively on the profitability (Buresh et al., 1997). The method of application can significantly influence the availability of added P fertilizer to the crop. Broadcasting (BR) of P fertilizer at low rates enhances P fixation by bringing the fertilizer into close contact with the soil (Sanchez and Salinas, 1981). Therefore spot application (SP) which minimizes contact between the fertilizer and the soil has been recommended for smallholder farmers in western Kenya. However, SP is laborious and hence less attractive to the farmers especially where labour is limiting. Moreover, there are conflicting reports on the superiority of SP over BR in increasing crop yields with some results suggesting that BR could in fact be superior to SP in P-fixing soils (Warren, 1992). †Corresponding author. Email: ptropala@yahoo.com