Effects of Integrated Use of Calliandra calothyrsus and Maize Stover with Urea on Soil Mineral Nitrogen, Striga Infestation and Maize Yields in Western Kenya

Abstract

This study investigated the effects of applying different combinations of two contrasting plant residues, Calliandra calothyrsus (Calliandra) and maize stover, with urea on Striga infestation and maize yield in western Kenya. A randomized complete block design (RCBD) with 12 treatments replicated four times was used. The following plant residue: urea combinations was used so as to supply a total of 75 kg ha-1 in each treatment combination; 75:0, 60:15, 45:30, 30:45, 15:60, and 0:75 for five seasons (2007-2009). A control treatment where no nutrient inputs were applied was included. Calliandra applied at 45 kg N ha-1 plus urea (30 kg N ha-1) and maize stover applied 15 kg N ha-1 plus urea (60 kg N ha-1) had consistently lower Striga infestation compared other treatments. Negative linear relationship between maize yield and Striga population were observed in the first three seasons i.e. 2007 LR, 2007 SR and 2008 LR. Overall mean maize grain yields over the five seasons were highest (3.0 t ha-1) under maize stover (30 kg N ha-1) combined with urea (45 kg N ha-1) followed by Calliandra (45 kg N ha-1) combined with urea (30 kg N ha-1) with (2.7 t ha-1). Maize stover (30 kg N ha-1) in combination with urea (45 kg N ha-1) increased maize grain yields relative to the control by 275%, 107% and 155% in the first, second and third seasons respectively. Treatments with Calliandra (45 kg N ha-1) in combination with urea (30 kg N ha-1) increased maize grain yields relative to the control by 191%, and 233% in the first and third seasons respectively. The control and sole maize stover (75 kg N ha-1) had the lowest yields across all the seasons. The optimum application rate for stover was 30 kg N ha-1 nitrogen equivalent while that for Calliandra was 45 kg N ha-1.