Combining biochar and PGPR as a replacement for soil fertilization is a practical approach to agricultural sustainability. Chemical fertilizers used in agriculture show a harmful impact on the ecosystem although we do rely on them to enhance agricultural production. The major drawbacks of sandy regosol are poor water and nutrition retention. In low-fertility soils, applying biochar as a soil amendment is feasible thus improving soil quality. However, biochar is not a substitute to fulfill the total fertilizer requirement. PGPR has been identified as an alternative fertilizer for increasing soil fertility. However, there is limited study on the effect of combine application of biochar and PGPR in field conditions. Therefore, this study was contemplated to determine the impact of lower rates of inorganic fertilizers combined with PGPR and biochar on leaf performance and kernal yield of maize grown in sandy regosols. The field study was conducted at Eastern University, Sri Lanka. There were eight treatments replicated three times in a RCBD experiment (Randomized Complete Block Design). Among the 8 treatments: four treatments combining sole PGPR (Azospirillum sp., Azotobacter sp., Phosphorous Solubilizing Bacteria (PSB) (Pseudomonas) and Potassium Solubilizing Bacteria (KSB) (Bacillus sp.) respectively with biochar and 50% Recommended Chemical Fertilizers (RCF), two treatments by combined PSB, KSB, biochar, 50% RCF with Azospirillum and Azotobacter respectively, a treatment combining biochar with 50% RCF, and control as RCF. Biochar was made by using coconut husk in a modified traditional kiln preparation technique and used at the rate of 8 t/ha. PGPR inoculants were used in field application at the rate of 300ml/acre. Triple Super Phosphate fertilizer (TSP), Muriate of Potash fertilizer (MOP) and urea fertilizer were used as RCF. All the agronomic practices were carried. At four weeks after planting (WAP) and 9 WAP leaf number was counted and leaf width and leaf length were measured. The kernals/ cob were counted at harvesting. All the data was subjected to analyze of variance (ANOVA) (α=0.05) based on the RCBD. Data evaluation was analyzed through “Mini tab” software statistical package. Mean separation was done with Turkey’s test. The results indicated that the co-inoculated Azotobacter combined treatment positively influenced on leaf performance and kernals yield of maize grown in sandy regosols.

Keywords: Biochar, Biofertilizer, PGPR, PSB, KSB.