M.Sc

The study entitled “Standardization of liquid formulation of PGPR mix–I and its evaluation for plant growth promotion in Amaranthus (Amaranthus tricolor L.)” was conducted in the Department of Agricultural Microbiology, College of Agriculture, Vellayani during the period 2016-2018. The main objectives of the study were standardization of liquid formulation of PGPR mix–I and its evaluation for plant growth promotion along with saving of chemical fertilizers in amaranthus.
The component cultures of PGPR mix-I, Azospirillum lipoferum, Azotobacter chroococcum, Bacillus megaterium and Bacillus sporothermodurans were procured from the Department of Agricultural Microbiology, College of Agriculture, Vellayani. All the isolates produced significant quantity of IAA under in vitro conditions. The nitrogen (N) fixers, Azospirillum lipoferum and Azotobacter chroococcum produced 40.31 and 36.43 ppm of IAA respectively, whereas Bacillus megaterium and Bacillus sporothermodurans produced 1.28 ppm and 3.36 ppm of IAA respectively.
The in vitro estimation of N fixation by N fixing organisms namely, Azospirillum lipoferum and Azotobacter chroococcum recorded a significant quantity of 21 and 14 mg N g-1 of carbon source respectively.
Quantitative assessment of solubilization of phosphorus (P) by Bacillus megaterium present in PGPR mix–I under in vitro conditions recorded 69.36 ppm, whereas qualitative assessment recorded a clearing zone of 8 mm and 12 mm diameter in NBRIP and Pikovaskayaˈs medium respectively. Similarly, in vitro assessment of K solubilization by Bacillus sporothermodurans recorded 12.18 ppm of potassium (K) and a clearing zone of 18 mm diameter in Glucose Yeast Agar medium.
Morphological and biochemical characterization of the isolates supported the genus level identification of the isolates.
An experiment was carried out to standardize the protocol for the preparation of liquid formulation of PGPR mix–I in completely randomized design with different treatments such as 2% Glycerol, 2% Polyvinylpyrrolidone (PVP), 15mM Trehalose, 1% Glycerol + 1% PVP, Glycerol (2%) + Trehalose (1%) + Yeast extract (1%) + PVP (1%) + Proline (1%) and control without any additives in four replications. Talc based formulation was kept as a standard. In spite of inconsistent viable count recorded in different treatments till eighth month, from ninth month onwards, formulation amended with 15mM Trehalose exhibited maximum viable count until fourteenth month. A significant decline of total viable population in talc based formulation was observed in each month compared to 15mM Trehalose amended formulation. Based on the population study, 15mM Trehalose amended formulation was adjudged as the best liquid biofertilizer formulation. Even after fourteenth month significant population was observed in 15mM Trehalose amended formulation and hence the shelf life studies of the same have to be continued.
A pot culture experiment was conducted in completely randomized design using sterilized soil under glass house conditions to test the efficacy of the best treatment ( liquid formulation amended with 15mM Trehalose ) with amaranthus as the test crop The seven treatments included 100% NPK as per KAU recommendation as chemical fertilizer alone, talc based or liquid formulation of PGPR mix–I each alone and with 100% and 50% NPK, control with additives without PGPR microorganisms and absolute control in three replications. Roots of seedlings were dipped in 2 per cent of the freshly prepared liquid formulation at the time of transplanting and 50 ml of 2 per cent liquid was drenched in the soil in each pot two weeks after transplanting.
The results indicated that the treatment T6- liquid formulation of PGPR mix–I+ 100% NPK recorded, maximum plant height of 37.54 cm, leaf number of 44.44 and leaf area index of 4.97 at harvest, but was on par with T3- talc based formulation of PGPR mix–I+ 100% NPK. The treatment T6 also recorded maximum fresh and dry weight of shoot (55.41 and 4.97 g plant-1 respectively)
and fresh and dry weight of root (6.6 and 0.56 g plant-1 respectively). However, the treatment T6 was found to be on par with T3 in these characters also. But T6 recorded the least oxalate content of 0.39 per cent as well. The treatment liquid formulation of PGPR mix–I + 50% NPK (T7) was found to be statistically on par with chemical fertilizer @ 100% NPK (T1) in parameters such as plant height, number of leaves, leaf area index, fresh and dry weight of shoot and root and oxalate content.
Application of treatments had significant effect on the soil available NPK content. Analysis of rhizosphere population after application of PGPR mix-I revealed successful colonization of organisms of PGPR mix-I in the rhizosphere of amaranthus.
The present investigation could standardize the protocol for liquid formulation of PGPR mix-I with 15 mM Trehalose as the best amendment. The study revealed that liquid formulation of PGPR mix–I is equally effective as talc based formulation of PGPR mix–I along with 100% NPK chemical fertilizers in enhancing yield and other biometric parameters of amaranthus. Compared to talc based formulation, the liquid formulation of PGPR mix–I showed higher shelf life beyond fourteenth month. The study also indicated that liquid formulation of PGPR mix–I + 50% NPK as chemical fertilizers was on par with chemical fertilizer @ 100% NPK and hence a saving of 50 per cent of chemical fertilizers could be advocated after confirmatory field trials.