Effectiveness of Organic Fertilizer and Rhizobium Biofertilizer in Improving Soybean Growth and Yield (Glycine max L. Merrill)

Abstract

Soybean productivity in Indonesia remains constrained by declining soil fertility and inefficient nutrient management. This study evaluated the effectiveness of Sokom organic fertilizer and Rhizobium biofertilizer, applied individually and in combination, on the growth and productivity of soybean (Glycine max L. Merrill). The experiment was conducted from October to December 2024 at the experimental field of the Faculty of Agriculture, Islamic University of North Sumatra, Medan, Indonesia, using a factorial randomized block design with four organic-fertilizer rates (0, 20, 25, and 30 tons/ha) and three Rhizobium application methods (control, seed soaking, and soil application). Observed parameters included plant height, flowering age, filled and empty pods, seeds per plant, and yield per plot. Organic fertilizer significantly affected yield, with the highest mean yield of 3.16 kg/plot at 20 tons/ha. Rhizobium seed soaking significantly accelerated flowering to 27.33 days. The interaction between organic fertilizer and Rhizobium significantly affected seeds per plant and yield, and the combination of 20 tons/ha Sokom with soil-applied Rhizobium produced the highest observed yield of 3.43 kg/plot. The principal advantage of this treatment was its ability to combine a moderate organic-fertilizer rate with biological nitrogen fixation, providing a practical option for reducing dependence on synthetic nitrogen fertilizer. For farmers under similar agroecological conditions, 20 tons/ha Sokom combined with soil-applied Rhizobium is recommended as the most promising treatment, subject to local validation and economic assessment.