IMPROVING SOIL FERTILITY AND SOYBEAN PRODUCTION BY GROWTH-PROMOTING BACTERIA IN DRYLANDS

Declining arable land for crop production is a major threat to Indonesia’s food security. Utilizing marginal land such as dryland for crop production is crucial. However, dryland has many limitations, such as low productivity and high variability of soil fertility. This study aimed to explore the beneficial effect of plant growth-promoting bacteria isolated from different organic materials such as compost in improving dryland fertility and soybean production. This study was started with compost preparation from maize and soybean biomass and plant growth-promoting (PGP) bacterial isolation and identification: indole acetic acid production, non-symbiotic N-fixing, and P-solubilizing. PGP assay was done qualitatively and quantitatively. Thus, a pot experiment was conducted in a completely randomized design with six treatments and four replications, including unsterilized and sterilized soil. This study showed that PGP bacteria inoculation, Bacillus aerophilus and B. subtilis, improved soybean production, specifically on seed dry weight (9.30%), N uptake (9.51%), and the number of soybean root nodules (17.24%). Compost application and the bacterial inoculation improved soil fertility, precisely the number of bacteria in unsterilized (29.03%) and sterilized soil (39.34%). However, a long-term application of organic materials and beneficial microorganisms (as biofertilizers) is crucial for supplying organic C and essential nutrients in drylands.