1Agricultural College and Research Institute, Tamil Nadu Agricultural University, Tiruchirappalli - 620 009 Tamil Nadu.
2Department of Microbiology, Tamilnadu Agricultural University, Coimbatore 641003.
*E-mail: thamizhvendan@yahoo.co.in, Tel: 91 431 2690692; Fax: 91 431 2690693.
Azospirillum bioinoculant is well known for its high nitrogen fixing and plant growth promoting characters. The carrier based bioinoculants generally suffer from shorter shelf life, poor quality, high contamination and low field performance. Therefore, it is desirable that new inoculant formulations be developed where liquid inoculants play a significant role. To develop liquid Azospirillum formulations the amendments viz., trehalose (10 mM), polyvinylpyrollidone (2%) and glycerol (10 mM) were added separately to N2 free malic acid broth. Addition of these amendments enhanced and maintained the population level at 108 up to 10 months of storage, whereas the control treatment (without any amendments) recorded this level only up to 3 months. Thus the liquid formulation has a shelf life of ten months, whereas the solid carrier based inoculant has a shelf life of only three to six months. Standardization of dosage of liquid formulation of Azospirillum for various inoculation methods and its survival was studied. The inoculum level of 10 ml/kg seeds, 150 ml/ha seedlings and 300 ml/ha were found to be the optimum dose for seed treatment, seedling root dipping and soil application methods respectively. The liquid formulation shows better adherence and survival on seeds, roots of seedlings and in the rhizosphere soil than the solid carrier based Azospirillum inoculant.
Azospirillum, Liquid formulation, Standardization
