Abstract
The aim of this work was to compare aggregate disruption of undisturbed soil samples by ultrasonic energy to aggregate disruption caused by the energy of simulated raindrops, to provide equations that can describe this relationship, and to evaluate whether aggregate stability, expressed by sonication method, may be used to estimate the effect that raindrops have on undisturbed soil samples. Undisturbed soil samples from A, Bi and C horizons of a Cambisol were submitted to different levels of ultrasonic energy and simulated raindrops. Sieved samples (aggregates) were also submitted to different levels of ultrasonic energy so that both disturbed and undisturbed conditions of samples could be compared. The results showed that the method using ultrasonic energy on undisturbed soil samples can simulate the amount of aggregate disruption of soil due to raindrop impact. Dispersion curves of disturbed samples may not be used to estimate the effect of raindrops on undisturbed soil samples.
Highlights
The impact of the raindrops on the soil constitutes the initial and most important phase of the erosive process
The objective of this work was: i) to evaluate the disaggregation of undisturbed samples of a typical Dystrophic Tb Haplic Cambisol (CXbd), resultant from the application of ultrasonic energy compared to the aggregate disruption that is caused by the kinetic energy of simulated raindrops; ii) to obtain a mathematical equation to express the relationship between the ultrasonic energy and kinetic energy of simulated raindrops; iii) to compare the results of disaggregation curves, obtained with application of ultrasonic energy, of samples with deformed structure and samples with undisturbed structure confined in coring cylinders
The undisturbed samples were saturated with distilled water by capillarity for 48 hours and later submitted to aggregate disruption by application of ultrasonic energy and by the kinetic energy of simulated raindrops
Summary
The impact of the raindrops on the soil constitutes the initial and most important phase of the erosive process. Several methods have been proposed for the evaluation of soil erosion, involving field work using natural or simulated rain (CARVALHO et al, 2007) and laboratory analyses based on soil attributes, especially, the stability of aggregates (COSTA et al, 2008). Sá et al (2000b), comparing aggregate stability evaluation methods, found that it does not just depend on the soil attributes, and on the methodology used in the analysis. Ultrasonic energy has been used for evaluation of the aggregate stability through dispersion curves, relating the amount of dispersed material in different levels energy (SÁ et al, 2002). That methodology has shown to be sensitive in detecting differences as to the soil aggregation influenced by physical, chemical, mineralogical attributes, Ciênc. That methodology has shown to be sensitive in detecting differences as to the soil aggregation influenced by physical, chemical, mineralogical attributes, Ciênc. agrotec., Lavras, v. 33, n. 3, p. 814-823, maio/jun., 2009
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