In recent years, the urease enzyme has been used to accelerate the natural precipitation of calcium carbonate (EICP) as a potential method of soil improvement. Optimizing the costs and scale-up is the main pitfall in facilitating the application of this method. Here, the efficiency of crude soybean extract as an alternative substance for purified enzymes has been investigated to reduce costs and achieve an environmentally friendly process. The urease activity of the soybean aerial organ was 9.355 × \(10^{(-3)}(\Delta Abs 340nm)/(\mu g protein ml^(-1) )\) , and for the soybean root was 6.056 × \(10^{(-3)}(\Delta Abs 340nm)/(\mu g protein ml^(-1) )\) . The ideal buffer for extracting the plant is phosphate buffer. The effect of time of adding reactants (CaCl2 and Urea) to the plant extract was investigated for the calcium carbonate precipitation process and the amount of sediment obtained. The highest uniaxial compressive strength of the improved soil sample obtained using the soybean aerial organ extract was equal to 380 kPa. The results of energy-dispersed X-ray spectroscopy and scanning electron microscopy indicate the effective binding of soil particles by calcium carbonate deposits. In conclusion, the crude plant extract can be a proper alternative to pure enzymes in the EICP method to improve soil.
