Abstract
Humic acid (HA) is a material that could be used to decrease erosion and improve soil structure. It is also known that biological soil crusts (biocrusts) have a major role in soil stabilization, but the mechanism is not well understood in the presence of HA, especially with mechanistic soil detachment rate parameters (b0 and b1) of the Wilson model, where b0 is the dimensional soil detachment parameter and b1 is the dimensional soil threshold parameter. Therefore, this study intends to (1) investigate the effect of different humic acid (HA) concentrations (0%, 4%, and 8%) on mechanistic soil detachment rate parameters (b0 and b1,) in the Tigris Riversides of the Gheraiat region, Baghdad City, Iraq, of the crusted versus uncrusted soils using a small scale model of the jet erosion tests (mini-JET) at different curing periods (1 week, 2 weeks, and 3 weeks), and (2) examine the impact of HA on b0 and b1 parameters versus some soil characteristics, such as electrical conductivity, cation exchange capacity, and soil organic matter for uncrusted and crusted soils. Thirty-six undisturbed soil specimens (18 for crusted soils and 18 for uncrusted soils) were acquired from the Tigris Riverbank. On these specimens, the mini-JET was used to determine the mechanistic cohesive soil erodibility parameters b0 and b1. The results showed that the value of b0 decreased up to 60% with an increase in curing times for crusted soils until they reached their optimum values at 2 weeks. There was no consistent pattern for b1 at different curing times. As the concentration of HA increased, the value of b0 decreased up to 86% and 99% for crusted and uncrusted soils, respectively. HA significantly improved electrical conductivity, exchange capacity, and organic matter in the soil and reduced soil erodibility. This study provides the benefits of adding HA to the soils as a soil stabilizer using a low-cost technique, which is the JET instrument.
Highlights
Humic acid (HA) is a major constituent of humic substances, which are the key organic components of soil, peat, coal, upland streams, dystrophic lakes, and ocean water
For a case without humic acid (Figure 3a) for uncrusted soil, the value b0 increased as curing time increased, whereas for biocrusts, the parameter b0 decreased until it reached its low peak after 2 weeks
A reduction in values b0 for crusted and uncrusted soils was observed in the presence of HA at 4% and 8% concentrations, as shown in Figure 3b,c, respectively
Summary
Humic acid (HA) is a major constituent of humic substances, which are the key organic components of soil, peat, coal, upland streams, dystrophic lakes, and ocean water. The addition of humic acid to the soil leads to an increase in the absorption of nutrients by the plant, as HA acts as a medium for transferring nutrients from the soil to the plant, especially in the case of soil drought [1,2]. By improving the soil properties and increasing the soil’s ability to hold water, HA increases the number of beneficial microbes in the soil, dismantles heavy soil granules, and enhances its physical, chemical, and biological qualities [3]. The dynamics of SOM are motivated by the addition of organic compounds that are transformed by a combination of physical, chemical, and biological factors as time progresses [5,6]. For example, play a role in the transport of cations between the organic−mineral complexes exchanged [7]
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