Growth of two cowpea [Vigna unguiculata (L.) Walp.] varieties as influenced by arbuscular mycorrhizal fungi and tithonia (Tithonia diversifolia Hemsl.) application under screen house conditions

The fragile nature of the tropical soils and several reports on its degradation have raised the need for a sustainable management that will increase production while maintaining a healthy soil and environment. There is possibility of varied responses by crop varieties to soil management strategies. Hence, the growth of two cowpea [Vigna unguiculata (L.) Walp.] varieties (IT97K-499-35 and IT97K-390-2) as influenced by soil amendment was determined in a screenhouse trial at the Department of Agronomy, University of Ibadan. A factorial combination of arbuscular mycorrhizal inoculation (with and without) and Tithonia diversifolia application (with and without) in a complete randomized design was used with three replications. Growth, yield and nutrient uptake parameters were determined and analysed using ANOVA. At eight weeks after sowing, IT97K-499-35 with tithonia application and mycorrhizal inoculation was significantly (P≤0.05) higher compared to the treatment without soil amendments. The application of tithonia without mycorrhizal inoculation significantly increased the pod dry weight and Ca uptake of IT97K-499-35 compared to that of IT97K-390-2 with similar treatments. However, the soil amendments significantly increased (P≤0.05) percentage root colonization of the two cowpea varieties compared to their respective control. The combined application of T. diversifolia and mycorrhizal fungi inoculation had a positive impact on the performance of cowpea. However, varied responses of the two cultivars to soil amendments call for screening of more cultivars to identify those with effective synergy to soil amendments in tropical low fertile soils.