PERFORMANCE OF SOYBEAN (Glycine max L.) INFLUENCED BY DIFFERENT RATES AND SOURCES OF PHOSPHORUS FERTILIZER IN SOUTH-WEST NIGERIA

Abstract

Low yields of soybean in Nigeria are attributed to many factors such as decliningsoil fertility and use of low yielding soybean varieties. Phosphorus is a soybeanplant growth-limiting nutrient.Therefore, application of phosphorus fertilizer atoptimum level is essential. Two experiments were carried out at Ibadan, Nigeria toestimate the optimum P-fertilizer rate for soybean and to investigate the responseof soybean to different sources of P fertilizer applied at the optimum rate. Thetreatments in the first experiment were two soybean varieties (TGX1987-10F andTGX1987-62F) and single superphosphate (SSP) fertilizer applied at five rates:0kgPha-1, 20kgPha-1, 40kgPha-1, 60kgPha-1 and 80kgPha-1. The treatments in thesecond experiment were: SSP, Tithonia compost (TC), poultry manure (PM),TC+PM, SSP+TC, SSP+PM applied at optimum P (40kgPha-1)rate obtained fromExperiment 1and control. Data collected on morphological parameters, grain yield(GY) and nutrient uptake were subjected to analysis of variance, the means wereseparated using least significant difference (p<0.05). Results showed thatTGX1987-62F (1.96Mgha-1) produced significantly higher GY than TGX1987-10F(1.26Mgha-1). Application of SSP at 40kgPha-1 produced tallest plants (131.8cm),highest number of leaves/plant (19.0), number of pods/plant (19.4), and GY(2.28Mg/ha) across the two varieties. Highest K-uptake (6.1mgplant-1) and Puptake(2.6mgplant-1) were obtained in plants treated with TC+SSP and SSP,respectively. The combination of TC and SSP at 40kgPha-1 produced highestnumber of flowers/plant (35.6), pods/plant (38.7) and GY (3.9Mgha-1). Acombination of Tithonia compost and SSP applied at 40kgPha-1 will increase grainyield of soybean in South-West Nigeria.