The response of maize to split application of urea and Tithonia diversifolia green leaf manure in western Kenya

Soils in western Kenya have lownitrogen and phosphorus due toinherent low soil fertilityaggravated by continuous croppingwith little or no use of fertilizers,leading to very low crop yields. Toincrease crop yields, it is necessary toadnutrients, particularly nitrogen andphosphorus. A study was carried out toassess split application of Tithoniadiversifolia green leaf manure as asource of nitrogen for maize. The aimwas to determine whether tithoniacould substitute urea as nitrogensource.A field experiment was conducted in aKandiudalfic Eutrudox soil atKhwesero, Butere District, westernKenya during long rains (April toAugust 1998) followed by a residualcrop during the short rains (September1998 to January 1999). Nitrogen, at therate of 60 kg N ha-1 was split andapplied at planting, and also at sixweeks after sowing as follows: 60:0,40:20, 20:40 and 0:60. Tithonia and ureawere used as nitrogen sources on both ow P (10 kg P ha-1) and high P (100 kgP ha-1) soils.Results for cumulative maize grainyields for two seasons were comparablewith either T. diversifolia or urea as thenitrogen source for maize in both lowand high P soils, suggesting thattithonia could substitute urea.However, with high P, application oftithonia at planting time gavesignificantly higher grain yields (5.4 tha-1) compared with the other Napplication timings. For urea, splitapplication of 1/3 at planting followedby 2/3 at six weeks later gave thehighest yield (6.1 t ha-1).In contrast with low P soils, tithoniashowed significantly lower yields whenapplied at planting (2.4 t ha-1)compared with the other N timings,which were similar.