Growth and nodulation of cowpea (Vigna unguiculata) in response to compost and inoculation with Glomus etunicatum and Bradyrhizobium

Abstract

Growth and nodulation of cowpea {Vigna unguiculata) inoculated with Glomus etunicatum and Bradyrhizobium IRc 25B were assessed in two cropping cycles in an Iwo series soil amended with farm waste compost in the greenhouse. In the first cropping, separate or dual inoculation of the test crop with two types of microorganisms had no significant effect on plant height but the treatments led to varying increases in nodule number, plant tissue phosphorus (P), nitrogen (N) and percentage of N derived from the atmosphere. Vesiculararbuscular mycorrhiza (VAM), when separately used, and rhizobium when used along with compost led to slight depressions in nodule weight. Glomus etunicatum, when used alone and in combination with rhizobium led to significant increases in root infection of the fungus but the root weights were not affected by the treatments. In the second cropping cycle, compost alone or when used in combination with VAM or rhizobium led to significant increases in plant height, compared with the control. Dual or separate use of the 2 microorganisms with or without compost led to marked differences in nodule number and weight, shoot and root dry weight, plant tissue P and N and N derived from the atmosphere. Pod number and seed weight were significantly increased by five fold over the control when the combination of VAM and compost was used. There was a progressive decrease in the nutrient levels after the first and second cropping. The endomycorrhiza used enhanced nutrient uptake while the added farm waste compost supplied additional nutrients.