The co-inoculation effect of Azotobacter spp. and Trichoderma asperellum with inorganic fertilizer on growth and yield of carrot

- Fertilizers play a prominent role in increasing the productivity of crops in the country. Phosphate solubilizing and nitrogen fixing microorganisms based biofertilizers can be used to reduce the inorganic nitrogen and phosphorous based chemical fertilizer usage and increase the plant availability nitrogen and phosphorous requirement. This study was aimed to use Sri Lankan isolates Azotobacter spp. and Trichoderma asperellum combination with lower rates of chemical fertilizers to evaluate their efficiency as biofertilizers for growth and yield characters of carrot. Further, possibility of combination use of both microorganisms were assessed. The pot experiment was carried out in Completely Randomized Design (CRD), consisting six treatments and four replications. The Treatments were namely T1 (No Fertilizer), T2 (100% NPK - DOA Recommendation), T3 (50% NP + K), T4 (50% NP + Azotobacter spp. + Trichoderma asperellum + K), T5 (75% NP +K) and T6 (75% NP + Azotobacter spp. + Trichoderma asperellum + K). The results of compatibility test resulted with 100% compatibility of Azotobacter spp. and Trichoderma asperellum isolates respectively. According to the results of pot experiment, best results of growth and yield parameters were observed from treatments T4, T6 and T2. The results of the present study reveals that combined use of Trichoderma asperellum and Azotobacter spp. with reduced levels of (25% and 50%) nitrogen and phosphorous based inorganic fertilizers could enhance the growth and yield of carrot equivalent or higher than those obtained by using full rates of Department of Agriculture Sri Lanka recommended inorganic fertilizers.