The role of organic manures in plant growth cannot be underscored. Organic manures have been shown to supply
the required plant nutrients, improve soil structure and water holding capacity, increase microbial population and
at the same time promote plant growth (Dauda et al., 2008). Findings of the current study support these
arguments. An increase in all measured growth parameters was observed with successive increase in bio-slurry
manure levels. Carrot plants treated with highest level (7.8 t/ha) of bio-slurry manure grew taller and had more
number of leaves than control plants. The higher plant heights and leaf numbers obtained in the current study
could be attributed to the ability of organic manure to supply the required plant nutrients and improve soil
structure and water holding capacity, thereby promoting plant growth. Similar to the findings of this study,
Mbatha (2008) also observed increased plant height and leaf numbers of carrots subjected to higher rates of
different organic fertilizers (chicken, kraal and compost). Nitrogen, phosphorous and potassium are essential for
good growth of plants. In the current study, higher plant heights and leaf numbers obtained could also be
attributed to better levels of major nutrients (N, P, and K) in the bio-slurry manure, as reflected by higher nutrient
levels in the growing medium at the end of each growing season. Hailu et al. (2008) similarly observed higher
plant height of carrots treated with organic P fertilizer (Orga) compared to control plants, which was attributed to
the ability of phosphorus to enhance early plant growth