Abstract
Soil compaction has been recognized as a severe problem in mechanized agriculture and has an influence on many soil properties and processes. Yet, there are few studies on the long-term effects of soil compaction, and the development of soil compaction has been shown through a limited number of soil parameters. The objectives of this study were to evaluate the persistence of soil compaction effects (three traffic treatments: T0, without traffic; T3, three tractor passes; and T5, five tractor passes) on pore system configuration, through static and dynamic determinations; and to determine changes in soil pore orientation due to soil compaction through measurement of hydraulic conductivity of saturated soil in samples taken vertically and horizontally. Traffic led to persistent changes in all the dynamic indicators studied (saturated hydraulic conductivity, K0; effective macro- and mesoporosity, εma and εme), with significantly lower values of K0, εma, and εme in the T5 treatment. The static indicators of bulk density (BD), derived total porosity (TP), and total macroporosity (θma) did not vary significantly among the treatments. This means that machine traffic did not produce persistent changes on these variables after two years. However, the orientation of the soil pore system was modified by traffic. Even in T0, there were greater changes in K0 measured in the samples taken vertically than horizontally, which was more related to the presence of vertical biopores, and to isotropy of K0 in the treatments with machine traffic. Overall, the results showed that dynamic indicators are more sensitive to the effects of compaction and that, in the future, static indicators should not be used as compaction indicators without being complemented by dynamic indicators.
Highlights
In recent decades, in agricultural production organized to meet the demands of an increasing population, the weight of agricultural machines has steadily increased, leading to soil compaction processes (Berisso et al, 2012).Soil compaction has been recognized as a severe problem in mechanized agriculture and has an influence on many soil properties and processes, as well as on crop yield (Servadio et al, 2005)
We hypothesized that static determinations such as total porosity (TP) and macroporosity derived from tension table measurements are not good indicators of soil compaction effects, and dynamic determinations such as K and effective macroporosity are well suited to establish these effects
The objectives of this study were to evaluate the persistence of soil compaction effects on pore system configuration, through static and dynamic determinations; and to determine changes in soil pore orientation due to soil compaction through the measurement of near-saturated hydraulic conductivity in samples taken vertically and horizontally
Summary
In agricultural production organized to meet the demands of an increasing population, the weight of agricultural machines has steadily increased, leading to soil compaction processes (Berisso et al, 2012).Soil compaction has been recognized as a severe problem in mechanized agriculture and has an influence on many soil properties and processes, as well as on crop yield (Servadio et al, 2005). Bulk density (BD) is used to evaluate the effects of traffic on soil quality (Petelkau, 1999; Arvidsson, 1999; Duttmann et al, 2014) This holds true only for a pure compaction process as variation of soil volume, but it does not include more complex processes like changes in pore orientation or tortuosity that result in no change in volume at all. These changes imply an intense deterioration of structure and homogenization of the pore system (Horn et al, 2003). Results obtained by Tarawally et al (2004) suggested that soil TP was not a good indicator of compaction effects, and that, it should not be used as a soil compaction index, as previously recommended by Al-Adawi and Reeder (1996), and later by Kuncoro et al (2014a)
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