Quantitative Modeling of the Potassium Release from Feldspar by Bacillus sp.

Potassium (K) is one of the essential nutrients for plant growth and it is found in the structure of many silicate minerals of soils. Soil microorganisms such as bacteria, fungi, algae and lichens have high efficiency in silicates decomposing and releasing elements such as potassium. The purpose of this study was to model and evaluate the effects of pH, incubation time and different amounts of feldspar on K release by Bacillus sp. For this reason different ranges of these three variables, including pH (5-9), incubation time (1-17 days) and feldspar (1-7 g.l-1) was considered and a central composite design with 20 experiments was used to evaluate the effects of the coded independent variables on K release from the feldspar. Results indicated that the central composite design has high efficiency (R2= 0.982, RMSE= 1.96mgl-1) in predicting soluble K concentration. Sensitivity analysis of the central composite design revealed that the pH and treated feldspar concentration are the most important factors in K release and the effect of these factors on K release are 37.48 and 31.80 percent, respectively. The highest concentration of the K was observed at high concentrations of feldspar and lowest levels of pH. Incubation time also had a significant effect on potassium release. In the early stages of the incubation time, the trend of potassium release was increased, in middle stages, K amount decreased but it was accelerated at the long times of incubation. Generally, increasing of the feldspar concentration and incubation time along with low initial pH lead to the high amounts of K release from feldspar.