## 4 Discussion  
Soil erosion, carbon sequestration, infrastructure rehabilitation, hazardous waste disposal, and water resources protection are all 21 st-century global challenges. Many of these challenges occur within or are supported by soil. The conventional perspective views soil as an infinite resource, composed of discrete functions, e.g., hydraulic, mechanical, and ecological, among others. However, soil is also a diverse ecosystem. The biotic potential in soil offers prospects for innovative and sustainable  
Figure 4: Urea concentrations measured in precipitation experiments following bacterial stimulation in soils from the Rotem Plateau. Figure 5: XRD patterns of precipitates produced by biostimulated soil (1) bacteria grown in CaCl\({}_{2}\) precipitation media. Counts in arbitrary units. CaCO\({}_{3}\) is calcite reference RRUFF R040070. solutions for some of these challenges. Harnessing natural biogeochemical processes to improve the environmental conditions and/or engineering properties of geological deposits has received significant attention in the scientific community [5; 22; 36; 38; 39]. Microbial-induced calcite precipitation (MICP) is one of the most promising biogeochemical treatments that effectively changes the hydromechanical and environmental properties of materials. Potential applications range from groundwater remediation and sequestration of radionuclides [40] to self-healing concrete [41]. For engineered materials, such as concrete, MICP can be achieved via bioaugmentation only, i.e., the introduction of monoclonal cultivated bacteria. In natural environments, such as soils, effective bioaugmentation by exogenous bacteria is not warranted, as the introduced bacteria are likely to decline in numbers due to low compatibility to the environment, as well as competition and predation by indigenous bacteria [18]. Moreover, producing and transporting large volumes of these cultures is an expensive and delicate procedure; their injection and homogeneous distribution throughout the treated site are difficult to achieve and might encounter regulatory hindrances. The ability to hydrolyze urea is widely distributed among indigenous bacteria in soils [15]. Hence, the biostimulation approach of MICP in soils is tangible. The main challenge with biostimulated MICP is inducing effective urea hydrolysis, which requires a sufficiently large ureolytic population. This challenge is even greater in nutrient-poor soils, where the initial bacterial abundance is low. Gat [31] showed that for MICP, effective biostimulation of an indigenous, ureolytic population in soil from a semiarid region (BSh (hot semiarid climate) in Koppen climate classification) requires an energy (carbon) source, in addition to urea. No ureolysis was observed in the absence of a carbon source. The authors showed significant changes to the indigenous bacterial population following biostimulation, where ureolytic bacteria population increased from 5% in the native sand up to 99% in carbon high dosage treatments. The primary goal of our research was to evaluate the potential of biostimulating urea-hydrolyzing bacteria in desert soils of the Rotem Plateau of the northern Negev Desert, Israel (BWh (hot desert climate) in Koppen climate classification), for soil erosion mitigation via MICP biocementation of the topsoil. We found that indigenous urea-hydrolyzing bacteria are naturally present in the desert soils and can be readily stimulated to achieve effective urea hydrolysis and calcite precipitation within days. These results are consistent with the results of [31]. It was also found that bacteria stimulation was not affected by differences in soil mineralogy observed between the two soils. [PERSON] [5] showed that urea hydrolysis could be effectively stimulated even at greater depths (10 m) using low doses of yeast extract and alkaline pH adjustment of the treatment media. Biostimulation rates in the desert soils were accelerated by providing a yeast extract dose of 1.0 g/L, whereas a lower dose of 0.1 g/L was found to be ineffective.