Optimization of Azolla pinnata biomass production on cattle manure slurry media: a batch culture greenhouse study

Abstract

Azolla biomass productivity is dependent on doubling time and relative growth rate and for its efficiency as N-biofertilizer, its nitrogen fixing potential is highly desirable. The present greenhouse study aimed to determine the ideal culture media conditions for optimal indoor Azolla pinnata production based on cattle manure through establishing the culture media that produces the highest Azolla biomass yield over the experiment time under greenhouse conditions and determine the culture media that sustains the maximum number of harvests before culture solution replenishment. Using batch culture solutions made up of four different treatments (dairy cattle slurry mixed in water) using a randomized complete block (RCB) design with three replicates. The parameters determined in this study were Azolla growth (biomass, RGR, and doubling time) parameters. All data was subjected to Analysis of variance (ANOVA). When differences between treatments were observed, the Tukey HSD post hoc test was used to separate the means using R software. Regression analysis was used to describe the response of relative growth (RGR) to increasing concentrations of cattle manure slurry in the culture media of A. pinnata. The regression equation obtained was differentiated to determine the optimal concentration of cattle manure slurry needed to optimize RGR in this study. The level for statistical significance was set at p < 0.05. The results revealed that Treatment T2 (0.25 liters of slurry: 4.75 liters water) produced the highest biomass of A. pinnata and also sustained productivity over three harvests compared to the other treatment level under the current experimental conditions. Secondly, based on the set concentration levels, the best ratio cattle manure slurry concentration in the culture media of A. pinnata was obtained at 0.25 liters to 4.75 liters of water. However, regression analysis revealed that the optimal concentration which maximizes relative growth rate of A. pinnata is achieved at a concentration ratio of 0.26 liters of slurry to 4.74 liters of water.