Influence of Minjingu rock phosphate on
biological nitrogen fixation and
performance of Lupin (Lupinus albus) in
Kabete, Kenya
Minjingu rock phosphate (MRP) could be a viable option to the expensive phosphatic fertilizers but its
solubility is low. The challenge therefore is to develop technologies that will accelerate P release from the
MRP for enhanced soil fertility and crop yields. It is envisaged that the use of lupin will boost the solubility
of rock phosphate and in-turn its biological Nitrogen fixation (BNF) and performance of lupin. A
completely randomized design will be used to evaluate the influence of lupin on MRP solubilization. MRP
will be applied at the rates of; 0kg ha-1, 30kg ha-1, 60kg ha-1 and 90kg ha-1 and mixed with 2kg of soil and
placed in pots on which lupin will be grown. Wheat to be used as a reference crop to aid in the
determination of BNF in lupin will similarly be treated. Soil will be sampled prior to planting and at harvest
and analyzed for P, N and pH levels using standard laboratory analytical procedures. Plants will be
sampled at harvest and similarly analyzed for N and P. Application of MRP on lupin will have a synergetic
effect in which the solubility of MRP will be enhanced and concomitantly its BNF and yield enhanced.
Key words: Biological Nitrogen fixation; Minjingu rock phosphate; Lupin; Reference crop