Document Type: Research Paper
ICAR-Central Tobacco Research Institute, Rajahmundry 533 105, Andhra Pradesh, India.
ICAR-CTRI Research Station, Kandukur, Andhra Pradesh, India.
ICAR-Central Tobacco Research Institute, Rajahmundry 533 105, Andhra Pradesh, India
Increased interests in low-input agriculture in recent years has seen the growing development
in the use of commercial biological inoculants to increase the mobilization of key nutrients such
as nitrogen (N), phosphorus (P) and potassium (K) to enhance their availability to crop plants.
The objectives of this field experiment with tobacco were to determine i) reduced rates of
inorganic fertilizer coupled with microbial inoculants that produce plant growth, ii) yield and
nutrient acquisition levels equivalent to those with full rates of fertilizers and iii) the minimum
level to which fertilizer could be reduced with the use of bioinoculants. The microbial
inoculants used were plant growth promoting bacteria viz., Azospirillum, Azotobacter, Bacillus
subtilis and Frateuria aurantia alone or a mixture of them in combination with 75% chemical
fertilizer. Results showed that supplementing 75% of the chemical fertilizer rate with inoculants
produced plant growth, yield and nutrient (N, P and K) acquisition that were statistically
equivalent to the full fertilizer rate without inoculants. When inoculants were used in single,
double or triple with 75% RDF the beneficial effects were usually not consistent. However,
inoculation with the mixture of PGPR (N, P and K mobilizers) at 75% RDF produced
significantly superior yield better than the full fertilizer dose without inoculants. Without
inoculants use of fertilizer rates lower than the recommended resulted in significantly less plant
growth, yield and nutrient uptake. The results suggest PGPR based inoculants can be used and
should be further evaluated as components of integrated nutrient management strategies.