RESPONSE OF GROUNDNUT (Arachis hypogaea L.) TO RHIZOBIA INOCULATION, NITROGEN AND PHOSPHORUS FERTILIZERS ON AN ALFISOL IN THE NORTHERN GUINEA SAVANNA OF NIGERIA

Thesis Abstract

ABSTRACT Groundnut (Arachis hypogaea L.) is an important leguminous crop in the Northern Guinea Savanna of Nigeria. This study aimed to investigate the response of groundnut to rhizobia inoculation, nitrogen, and phosphorus fertilizers on an Alfisol in this region. A field experiment was conducted using a randomized complete block design with a factorial arrangement of treatments. The treatments included two levels of rhizobia inoculation (with and without), three levels of nitrogen fertilizer (0, 40, and 80 kg N/ha), and three levels of phosphorus fertilizer (0, 20, and 40 kg P/ha). The results showed that rhizobia inoculation significantly influenced groundnut growth and yield parameters. Plants inoculated with rhizobia exhibited higher plant height, number of branches, pod yield, and haulm yield compared to non-inoculated plants. This indicates the importance of rhizobia in enhancing groundnut productivity in the region. Nitrogen application also had a significant effect on groundnut growth and yield. The plants treated with 80 kg N/ha showed the highest pod and haulm yields, indicating the positive impact of nitrogen fertilizer on groundnut production. However, excessive nitrogen application beyond 80 kg N/ha did not result in further yield increase, suggesting an optimal nitrogen rate for groundnut cultivation in the Northern Guinea Savanna. Similarly, phosphorus fertilization significantly influenced groundnut growth and yield parameters. Application of 40 kg P/ha resulted in the highest pod and haulm yields, indicating the importance of phosphorus in groundnut production on Alfisols in the region. However, lower levels of phosphorus (20 kg P/ha) also showed a significant improvement in yield compared to the control, highlighting the need for balanced phosphorus fertilization for optimal groundnut production. Overall, the interaction of rhizobia inoculation, nitrogen, and phosphorus fertilizers showed a significant influence on groundnut growth and yield. The combined application of rhizobia with nitrogen and phosphorus fertilizers resulted in the highest pod and haulm yields, indicating the synergistic effects of these factors on groundnut productivity. Therefore, integrated nutrient management practices including rhizobia inoculation and balanced use of nitrogen and phosphorus fertilizers are essential for sustainable groundnut production in the Northern Guinea Savanna of Nigeria.