Production of biofertiliser from soybean cake and soypod

Soil fertility can be improved by the use of fertiliser, from chemical or biological sources. Excessive use of chemical fertiliser has caused a large number of environmental pollutions in water, air and soil. This research aimed to produce organic fertiliser from soybean cake and pod using Solid State Fermentation (SSF). Soybean cake and pod samples from WASIL Oil Company, Sagamu, Nigeria, underwent NaOH pretreatment for delignification. Physico-chemical parameters, including temperature, Total Dissolved Solids (TDS), moisture content (MC), pH, phosphate, potassium, calcium, nitrate, and sulphate, were analyzed using standard methods. Microbial populations were determined through agar plate and broth culturing, while SEM, FTIR, and EDX analyses were conducted on raw and pretreated samples. Results showed that for soybean cake, temperature was 28.50 °C, TDS 34.9 mg/l, MC 58.4%, pH 7.56, phosphate 2.81 mg/l, potassium 2.50 mg/l, calcium 38 mg/l, nitrate 2.69 mg/l, and sulphate 32 mg/l. For soybean pod, values were 28.40 °C, 33.1 mg/l, 51.2%, 7.06, 2.90 mg/l, 2.8 mg/l, 41 mg/l, 2.84 mg/l, and 36 mg/l respectively. Microbial counts for soybean cake included Salmonella (2.4×10⁴), E. coli (2.1×10⁴), Bacillus (2.7×10²), and Aspergillus (3.7×10²), while the soybean pod showed Salmonella (1.9×10⁴), E. coli (2.1×10⁴), Bacillus (2.4×10²), and Aspergillus (3.4×10²). SEM revealed irregular morphological shapes at the surface layers. FTIR confirmed the presence of amine and carboxyl groups indicative of fertilisers, while EDX detected nitrogen, phosphorous, and other nutrients. The study concluded that SSF is suitable for the production of effective and economical organic fertiliser from soybean cake.