Influence of Plant Growth Regulators, Varieties and Phosphorus Levels on the Growth and Flowering 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 of plant growth regulators, varieties and phosphorus levels on the growth and flowering of some varieties of cowpea (Vigna unguiculata L) during 2018, 2019 and 2020 rain fed cropping seasons. The treatments consisted of four 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 number of days to first flowering, number of days to 50 % first flowering, crop growth rate, net assimilation rate and grains yield. Data collected were subjected to analysis of variance (ANOVA) and means were separated using Least Significant Difference (LSD) at 5 % probability level. The results show that application of plant growth regulators (PGRs) was not significant on all the parameters measured. Varietal effects were significant on all the parameters measured. All the erect and semi erect varieties (SAMPEA-7 and SAMPEA-14) produced higher growth rate (crop growth and net assimilation rate) over the local cultivar (“kanannado”). SAMPEA-14 recorded least number of days to first and 50 % flowering; and grains yield was also higher on SAMPEA-14. Effect of phosphorus fertilizer application was highly significant on all the parameters measured. Application of 45 kg P2O5 ha-1 gave the highest crop growth rate and induced early flowering. Higher grains yield was also obtained with the Application of 45 kg P2O5 ha-1 . There was highly significant interaction between PGRs, varieties and phosphorus levels on crop growth rate per plant, net assimilation rate per plant and number of days to first flowering. For the best yields, application of brassinolite and 45 kg P2O5 ha-1 on SAMPEA-14 was found to be realistic and is hereby recommended for the farmers to adopt in Yola, Adamawa State Northern Guinea Savannah zone of Nigeria.