Rhizobium Inoculation Combined with Organic Ameliorants and Mineral Fertilization Improves Soybean Growth and Productivity in Tidal Swamp Soils

¹ Department of Agronomy and Horticulture, IPB University, Bogor, Indonesia
² Department of Agronomy, Universitas Sriwijaya, Palembang, Indonesia,
³ Doctoral Program, Department of Agriculture Science, Universitas Sriwijaya, Palembang, Indonesia

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Soybean (Glycine max L.) productivity in tidal swamp soils is constrained by soil acidity, low nutrient availability, and poor soil fertility. This study evaluated the interactive effects of mineral fertilizer levels and different combinations of organic ameliorants and Rhizobium inoculation on soybean growth and productivity under tidal swamp conditions. The experiment was arranged in a two-factor factorial randomized complete block design consisting of three mineral fertilizer levels (0, 50%, and 100% of the recommended rate) and four ameliorant-Rhizobium treatments: no ameliorant (A0), organic ameliorants (cattle manure + purun grass compost) (A1), organic ameliorants combined with Rhizobium inoculation (A2), and Rhizobium inoculation alone (A3). Data were analyzed using analysis of variance (ANOVA), followed by Duncan's Multiple Range Test (DMRT) at the 5% significance level. Significant interactions between mineral fertilization and ameliorant treatments were observed for several growth and yield parameters. The combined application of the full mineral fertilizer rate with organic ameliorants and Rhizobium inoculation (P2A2) produced the highest plant height (56.27 cm at 8 weeks after planting) and the highest percentage of filled pods (approximately 94–95%). In contrast, Rhizobium inoculation without organic ameliorants resulted in lower performance under high fertilizer application, indicating that soil improvement was essential for maximizing biological nitrogen fixation. Organic ameliorants improved soil conditions, enhanced rhizosphere activity, and increased the effectiveness of Rhizobium inoculation, resulting in superior soybean growth and reproductive performance. These findings demonstrate that integrating Rhizobium inoculation with organic ameliorants and balanced mineral fertilization is an effective strategy for improving soybean productivity in acidic tidal swamp soils.