Effects of empty fruit bunch biochar and nitrogen–fixing bacteria on soil properties and growth of sweet corn

Empty fruit bunch (EFB) biochar is being used as soil amendment to improve soil productivity of infertile soil for enhanced plant growth. Tropical soils are generally unfertile with, low organic matter, plant nutrients, acidic and low microorganisms that affect crop production. Addition of biochar such as empty fruit bunch (EFB) could improve the soil fertility. Laboratory and glasshouse studies were conducted to determine the effect of EFB biochar and nitrogen-fixing bacteria Stenotrophomonas sp. (Sb16) on soil microbial communities, enzyme activity, chemical properties and growth of sweet corn. Five rates of EFB biochar (0, 0.25, 0.5, 0.75 and 1%) were applied to soil either with or without bacteria Sb16 and incubated for 40 days under laboratory condition. Sweet corn were grown in pots containing 6 kg soil and applied with five rates of EFB biochar (0, 5, 10, 15 and 20 t/ha) with or without bacteria Sb16. The experiment was arranged in a randomized complete block design (RCBD), with 5 replications. Results of laboratory study showed that combination of EFB biochar at 0.5% without inoculation and 0.25% with bacteria Sb16 in both soil, significantly increased populations of soil bacteria, fungi, actinomycetes and N2 -fixing bacteria (NFB), enzymes (urease, acid phosphatase and fluorescein diacetate (FDA) hydrolysis activity), and soil chemical properties (pH, organic carbon, total N, available P and exchangeable K, Ca and Mg). The glasshouse experiment showed that application of EFB biochar at 5 t/ha with bacteria Sb16 significantly (p<0.05) improved growth of corn (shootand root biomass, root length, root volume, plant height, leaf chlorophyll content and nutrient uptake). Addition of higher EFB biochar to soil negatively affected all the observed parameters. The studies showed that application of EFB biochar at 5 t/ha or 0.25% with N2-fixing bacteria Sb16 and 10 t/ha or 0.5% without bacterial inoculation improved corn growth and the quality of soil for sustainable corn production.