PhD Thesis
Studies were conducted at Bumbwi, Mtwango and Kizimbani villages of West District in
Zanzibar to evaluate the fertility status of the soils, and their suitability for rice production
and the response of rice (Oryza saliva L. var. NERJCAX2) to nitrogen (N), and phosphorus
(P). Composite soil samples (0-30cm) were collected from Bumbwi. Mtwango and
Kizimbani villages and analyzed to establish their fertility status. Field experiments were
conducted at each site at (Bumbwi, Mtwango and Kizimbani) to assess the response of rice
to N and P and NxP interaction to establish the optimal economic production of the Rice
variety-NERICA No 12 and the residual effects of nitrogen and phosphorus on subsequent
rice yields were assessed. The experimental design was a Randomized Complete Block
Design (RCBD) with three replications at each site. Phosphorus was applied at the .ates of
0, 20, 40, 80 and 120 kg P ha’1 at planting time and nitrogen was applied at the rates of 0,
50, 100, 150 and 200 kg N ha’1, in two equal splits applied at two weeks after seedling
emergence. Determination of the residual effects of N and P involved growing of rice
during second and third seasons on treated plots without further application of N and P.
Data were collected on the response of rice variety NERICA No. 12 to different rates ofN
and P and their combinations. The nutrient status of the soils at the study areas were low in
total nitrogen (0.01 to 0.1 %) and zinc (1.0 mg Zn/kg); medium in phosphorus (7 to 20 mg
P/kg). The N and P fertilizer significantly (P<0.001) increased grain yield (5.73 t ha’1),
with 200 kg N ha ’’ and 80 kg P ha’1. The residual effects of N and P, significantly
(PO.OOl) increased rice yield during 2012/13, 2.70 to 5.56 t ha’1, 3.26 to 5.73 t ha’1 and
2.93 to 5.70 t ha'1, 2013/4 cropping seasons, 2.40 to 4.60 t ha’1, 2.46 to 4.90 t ha-1,and 2.50
to 5.90 t ha'1 and 2014/5 cropping seasons and 1.90 to 3,50 t ha’1, 2.26 to 3.53 t ha’1 and
2.23 to 3.5 t ha’1 at Mtwango, Bumbwi and Kizimbani respectively.