Effects of Varieties, Plant Growth Regulators and Phosphorus Levels on Root, Nodulations and Yield Response of Cowpea (vigna Unguiculata (l.) Walp) in Yola, Adamawa State, Nigeria

The experiments were conducted at the Teaching and Research farm of the Department of Crop Production and Horticulture, Faculty of Agriculture, Modibbo Adama University Yola, to investigate the effects varieties, plant growth regulators and phosphorus levels on the growth and yield of cowpea (Vigna unguiculata L) during 2018, 2019 and 2020 raining seasons. The treatments consisted of four different plant growth regulators (Cytokinins, gibberellins, brassinolite and water sprays), four levels of phosphorus fertilizer (0, 15, 30 and 45 kg P2O5 ha-1 ) and three cowpea varieties (SAMPEA-7, SAMPEA-14 and red “kanannado”) which were factorially combined and laid out in a Split-Split Plot Design replicated three times. Data were collected on root length, number of nodules, number of effective nodules and grains yield. All data collected were subjected to analysis of variance (ANOVA) and means were separated using Least Significant Difference (LSD) at 5% probability level. Results showed that, application of cytokinins recorded significantly higher root length, gibberellins recorded the highest number of nodules per plant while the application of plant growth regulators did not significantly influence number of effective nodules per plant and grains yield. Each variety performed differently in terms of the growth parameters measured. SAMPEA-14 produced higher root length and grains yield than the rest of the varieties while SAMPEA-7 produced the highest number of nodules and number of effective nodules per plant. Significantly higher root length, number of nodules, number of effective nodules and grains yield was obtained in the application of 45 kg P2O5 ha-1 . There was highly significant interaction (P≤0.01) between PGRs, varieties and phosphorus levels on root length and number nodules per plant. For the best grains yield, application of 45 kg P2O5 ha-1 on SAMPEA-14 recorded a promising yield and are hereby recommended for the farmers in Yola, Adamawa State Northern Guinea Savannah zone of Nigeria.