Aggregate breakdown and dispersion of soil samples amended with sugarcane vinasse

Abstract

Soil aggregation is a very complex issue related to important soil attributes and processes. The aggregate breakdown and dispersion of soil samples amended with sugarcane vinasse were evaluated using ultrasonic energy. Vinasse is an important byproduct of sugarcane industries, intensively applied to soils in Brazil as liquid fertilizer. Samples of two Oxisols and one Ultisol were used in this study. The physical and chemical characterization of soils was performed, and the 1 to 2 mm size aggregates (200 g) were packed in PVC columns (6.0 cm high and 4.0 cm internal diameter) and incubated with sugarcane vinasse under lab conditions for 1, 30 and 60 days. After incubation, aggregates were submitted to levels of ultrasonic energy, and the particle size distribution (53 to 2,000 µm, 2 to 53 µm, and < 2 µm fractions) was quantifi ed.Mathematical equations were used to relate the mass of aggregates in each of these fractions to the applied ultrasonic energy, and parameters related to aggregate stability were then obtained.Soils showed an aggregate-hierarchy resulting in a stepwise breakdown under ultrasonic agitation. Considering this soil-aggregation hierarchy, vinasse contributed even in a short time to the bonding between and within 2 to 53 µm aggregates, mainly in the Oxisols. This may be related to organic compounds present in the vinasse, cementing soil particles. Potassium enrichment of soil samples did not contribute to soil dispersion.

Potential effects of vinasse as a soil amendment to control runoff and soil loss

“…In addition, whenever vinasse is applied to silty loam soil, a part of it fills the voids of soil, and other parts stay on the soil aggregates surface. The effects of vinasse may be temporary, since the organic compounds in vinasse are highly degradable from vinasse cementing the microaggregates and favoring the flocculation of clay fraction (Ribeiro et al, 2013).…”

“…Vinasse, like other organic fertilizers, has high organic matter, N, and K contents (Madejón et al, 2001), which promotes nutrient recycling in ecosystems, and causes less environmental impacts during production. It is an important byproduct of the ethanol and sugarcane industries and is intensively applied to soils in Brazil as liquid fertilizer (Ribeiro et al, 2013). However, the direct application of vinasse is constrained by its high salinity and high density of organic matter and other chemical materials.…”

“…Many studies have been performed to identify the effects of vinasse application on growth, development, and production of sugarcane and the physical properties of soil (e.g., Tejada et al, 2009;Jiang et al, 2010;Prado et al, 2013;Ribeiro et al, 2013), but very few studies have investigated the effects of application of vinasse on surface runoff and water soil loss rate. According to previous studies Gonzalez, 2006a, 2007;, the application of beet vinasse had unfavorable impacts on some soil properties, viz.…”

Factors affecting clay dispersion in oxisols treated with vinasse

“…Iron oxides are known flocculant agents and their higher content may also have contributed to the absence of response in clayey soil (Table 1) (RIBEIRO et al, 2013). It is known in the pH CaCl 2 range of this experiment (4.98 -6.33) that iron oxides have net positive charge and the presence of particles of opposed charges favors flocculation, because there is no electrostatic barrier between them to keep the system dispersed (TREFALT et al, 2014).…”

“…Organic compounds, charges in mineral particles and adsorbed cations can affect the stability of a clay suspension, changing the stability of aggregates, which are important for the maintenance of soil physical quality (RIBEIRO et al, 2013;VICENTE et al, 2012). Clay flocculation is the initial process of soil aggregation and is mainly affected by electrostatic forces (CARDOSO et al, 2013;CHOROM;RENGASAMY, 1995).…”