Residual Effect of Phosphorus Fertilizer on Yield of Pigeon Pea (Cajanas cajan) in Ultisol

Phosphorus (P) is one of the essential plant nutrients and plays an important role in nitrogen fixation of leguminous crops. A two-year experiment was conducted at the Teaching and Research Farm of Ambrose Alli University, Ekpoma, Nigeria to investigate the effect of different rates of phosphorus fertilizer on the growth, yield, nodulation and nutrient uptake of pigeon pea (Cajanas cajan). Seven P rates (0kg (control), 25, 50, 75, 100, 125 and 150kg ha-1) were laid out in a Randomized Complete Block Design with three replicates and managed for two consecutive years. Data on plant growth, yield, nutrient uptake and soil properties were collected for the two seasons. The application of phosphorus significantly increased the soil nutrient content after the first season. There was no significant difference in height and stem girth of pigeon pea. The application of 75 kg ha-1 significantly (p=.05) increased the number of leaves, biomass and nodules of pigeon pea. The application of 25 - 75kg ha-1 of phosphorus fertilizer increased the grain yield of pigeon pea than other rates of application in the first cropping season. In the residual experiment, the control and 25kg ha-1 application of P had the grain yield of 1,493.3kg ha-1 and 1,498.0kg ha-1 respectively, and were significantly (p=.05) higher compared to other treatments. The application of phosphorus fertilizer at the rate of 25 – 75kg ha-1 significantly improved the yield, nodulation and nutrient uptake of pigeon pea in degraded ultisol. Increasing the quantity of P fertilizer above 25kg ha-1 showed no significant difference in the yield of pigeon pea, it will be more ideal to use 25kg ha-1 as the recommended rate.