Responses of Anabaena azollae for difierent organic fertilizers; cow dung and banana peel water

Abstract

Organic farming is becoming popular around the globe due to increased public consciousness related to human health risks and environmental impacts associated with using commercial inorganic fertilizers. Nitrogen (N) limitation in organic fertilizers is one of the main constraints which discourage farmers from using them in their fields. Azolla sp. is a floating aquatic fern that contains 4-596 of N content from its dry weight. Furthermore, the presence of symbiont Anabaena azof/ae (cyanobacteria) enhances the N content through the N- fixation. Therefore, Azofla sp. is a potential N source in the production of organic fertilizers. This study aimed to determine the responses of both Azolla sp. and Anabaena azo//ae in liquid cow dung (CD) and banana peel (BP) water and finally to determine the better medium for the growth ofAzof/a sp. The 0.25g of Azo/la sp. was cultured in each water (control) and two treatments such as liquid CD, and BP in a concentration series with triplicates. The CD and BP treatment series were prepared with changing volume ratios such as, 1:0 (TO), 1 :1 (T1), 1:2 (T2), 1:3 (T3), 1:4 (T4) and 1:5 (T5). The biotic parameters ofAzo//a sp. (wet weight, surface area, relative growth rate and total nitrogen content) and Anebaene azollae (heterocyst frequency (HF) and the total number of Anabaena filaments (TF)) were measured at three-day intervals throughout the experiment. Additionally, the water quality parameters (pH, temperature, conductivity, turbidity and salinity) were measured at three-day intervals during the 21 days of the experimental period.The significantly high wet weight (0.314 g),surface area (16.097 cm2) and relative growth rate (0.012 g/g/day) ofAzo//a sp. were recorded at TO in the BP series (p<0.05). Also, the highest total nitrogen content (TN) of Azo/is sp. was recorded as 3.092 mg N/mg in TO of the BP series where only the liquid CD was available in the growth media. The rapid growth ofAzo/fa sp. was observed in that treatment within the first 02 weeks. When considering the measurements of Anabaena azollee, the maximum HF was recorded as 19.35 96 in TO of the BP series while the highest TF was reported as 21 in both T1 in the CD series andT0 in the BP series. A moderately strong correlation (r= 0.3548) was recorded between the HF of Anabaena azollae and the total nitrogen content (TN) of Azo/la sp. Additionally, the RGR ofAzo//ssp. showed a significant positive correlation with both TF and HF of Anabaena azollae under both treatment series. For example, the BP series showed a strong correlation between TF and RGR(r=0.887, p=0.000) (R2 = 78.4696) as welt as between HF and RGR (r = 0.726, p=0.000) (R2 = 52.5596). These correlations indicate the potential use of RGR of the Azolla sp. Which is easy to measure to use in predicting/extrapolating microscopic observations such as HF or TF of Anabaana azollee. Overall, our results suggested that the fertilizer with only cow dung (CD) was the best treatment for increasing the growth and the total nitrogen content ofAzo/la sp. These insights help to develop organic fertilizers using “Azo/la - Ane6aena” the existing Pteridophyte — Blue green algae ecological interaction.