Abstract:
In the forest zone P is one of the major yield-limiting nutrients in most of the well drained
soils. In this study, attempts were made to improve the phosphorus and calcium status of
the soil for maize production through the use of ground Togo phosphate rock (TPR). Since
TPR is unreactive, it is therefore necessary to allow for a time lag between time of application
and nutrient availability. The possibility that legumes may enhance the dissolution of
TPR was also considered. The experiment was started in the minor season of 1998. Initial
soil properties showed that the soil was acidic with a very low content of available phosphorus.
The experimental design was a split plot. Surface broadcast and broadcast incorporation
were the main plot treatments. Four rates of TPR viz. 400, 600, 800, and 1,200
kg ha-1 and two checks (Control and 200 kg ha-1 SSP) constituted the subplot treatments.
All the treatments (only in the major season) received 30 kg N ha-1 and 30 kg K20 ha-1 at
planting and a second dose of 20 kg N ha-1 six weeks after planting. SSP was applied directly
to maize in the major season, while TPR was applied only to cowpea in the minor season.
For the three year running, cowpea grain yield was similar for all the subplot treatments.
Incorporation gave a significantly higher cowpea grain yield only in the first year. While
maize grain yield was similar for all the treatments in the first year, SSP (4.47 t ha-1), 800
kg TPR ha-1 (4.59 t ha-1), and 1,200 kg (4.35 t ha-1 ) gave a significantly higher yield than
the control (3.19 t ha-1 ) in the second year. Significant improvement of soil properties such
as available P and exchangeable calcium by the TPR 800 and 1,200 kg ha-1 treatments suggests
that these treatments can support a higher maize yield if rates of Nand K are
increased.
