RESPONSE OF SOYBEAN (Glycine max (L.) Merrill) TO METHODS AND TIME OF RHIZOBIAL INOCULATION IN ABEOKUTA, SOUTHWESTERN NIGERIA

Abstract

This study investigated the effect of time and methods of rhizobial inoculation on growth and nodulation of soybean in the screenhouse. The experiment was a 4 x 2 factorial, arranged in completely randomized design with three replications. The treatments were 2 methods of rhizobia inoculation and 4 levels of time of application. The liquid (broth culture) and solid inoculants were applied at different time intervals, at sowing (0 week), 1, 2 and 3 weeks after planting (WAP), respectively. Observations were made on plant height, number of nodules (primary and secondary), root weight, shoot weight, number of pods, number of leaves, nodule dry weight, pod dry weight at 8 WAP and grain yield per plant at harvest. Application of liquid inoculant gave the highest value in almost all the parameters measured compared with solid inoculants. The liquid inoculant gave 100, 60 and 40.3% increase in secondary nodules, total nodule count and grain yield, respectively, over the solid inoculant. The time of inoculant application significantly (p < 0.05) affected shoot weight, number of pods, number of leaves and grain yield per plant of soybean. Generally, inoculation at sowing gave the best performance in most of the agronomic parameters measured with either solid or liquid inoculants. However, plants that received liquid inoculant gave highest number of pods and grain yield at 2 WAP which amounted to 46.7 and 70.6% increase, respectively, over inoculation at sowing.  It is, therefore, concluded that application of liquid rhizobial inoculant at 2 WAP could enhance optimum production of soybean.