Abstract:
We investigated the response of cowpea (Vigina unguiculata (L.) Walp) to
integrated soil fertility management (ISFM) on nodule formation, growth and
nitrogen fixation in two field sites with contrasting rainfall amounts in a semi-arid
environment. Treatments used included an unamented control, manure, TSP and
manure+TSP. Results indicated that nutrient amendments were most effective during
the drier rain season compared to the wetter season. In addition, combination of
organic and inorganic amendments was more effective during the drier rain season.
Further, low rainfall severely reduced nodule and shoot biomass but not root biomass.
So far we concluded that nutrient addition could be necessary for cowpea growth
during drier seasons. Assessment of biological nitrogen fixation (BNF) revealed a
BNF of between 46 to 53% with significantly (p<0.05) higher N fixed in wetter
compared to the drier study site. We further concluded that BNF was reduced by low
rainfall amounts which also lowered nodulation and shoot biomass.
