Abstract:
Paddy cultivation predominantly depends on inorganic fertilizers due to the limited availability
of high-quality organic alternatives. Cyanobacteria have emerged as a widely accepted tool in the
agriculture sector, due to their macro and micronutrient profiles. Among these Nostoc stands as a
popular nitrogen fixing cyanobacteria, capable of surviving, in both terrestrial and aquatic
environments. In this study, a pot experiment was conducted to find the potential of Nostoc grown
in parboiled water, in combination with either organic or inorganic fertilizers, on the growth, yield
and residual nutrient content in soil. The experimental design was CRD with five treatments,
namely T1 – control, T2- 100 % IF (inorganic fertilizers), T3- 100 % OF (organic fertilizers =
compost), T4- Nostoc + 50 % IF except N, + Nostoc foliar application (NF), T5- Nostoc + 50 %
compost + NF and three replicates. Data was analyzed by SAS with LSD mean separation at P=0.05.
Various growth parameters, such as plant height, leaf numbers per plant, number of effective
tillers and grain yield were measured. Additionally residual nitrogen, phosphorus, potassium and
carbon content of the soil was measured after paddy harvesting. The results revealed that Nostoc
combination treatments (T4 & T5) exhibited significantly higher values in leaf numbers (T4-31.99
and T5-32.11 @ 6th week), effective tillers (T4-5.44 and T5-5.56), and residual nutrient content
of available nitrogen (T4-12.96 ppm and T5-16.83 ppm), phosphorous (T4-11.26 μg/g and T5-
17.37 μg/g), potassium (T4-509.45 μg/g and T5-501.25 μg/g) and total carbon(T4-3.75 μg/g and
T5-3.84 μg/g) compared that of sole inorganic (T2-26.99, 4.56, 5.329ppm, 3.09μg/g,
461.17μg/g,3. 47μg/g respectively) or organic treatments (T3-30.34, 4.44, 7.61ppm, 18.83μg/g,
413.59μg/g, 3.93μg/g respectively). Notably T4 (11.22g/plant) recorded the highest grain yield
while T2 (10.36) and T5 (10.02g/plant) yielded comparably. The results therefore highlighting
the potential of Nostoc to substitute the inorganic nitrogen application and to cut down 50% of P
and K inorganic fertilizers in paddy cultivation. In addition, 50% of the compost also could be
substituted by Nostoc in the organic paddy cultivation. Further, Field level studies are suggested
in different agroecological conditions, to find the suitability of Nostoc as a biofertilizer.
