Abstract

Yields of maize, melon, cassava and cowpea as well as changes in soil chemical contents were examined under different fertilizer treatments in a mixed cropping system. The results showed that fertilizer treatments had significant effects on the yields of maize, cassava and cowpea but no significant effect on melon yield. Total nitrogen decreased in all the plots after cropping and available phosphorus reduced from initial value of 4.72 mg/kg to between 3.37 mg/kg where no fertilizer was added and 3.83 mg/kg under inorganic fertilizer. Exchangeable potassium decreased in all the plots irrespective of fertilizer type and the changes ranged between 25% under organic fertilizer and 53% under inorganic fertilizer treatment. The level of organic carbon decreased by about 17% under organic fertilizer but by 59% where inorganic fertilizer was applied. Calcium (Ca) and magnesium (Mg) increased by 21% and 20%, respectively with the application of organic fertilizer. Though yields of crops increased with application of inorganic fertilizer, organic fertilizer and combination of both in this experiment, changes in soil nutrients status after cropping showed that the fertilizer rates used might not be able to sustain soil fertility under the system.

Key words: Organic fertilizer, inorganic fertilizer, mixed cropping.