Hydraulic Properties and the Water-Conducting Porosity as Affected by Subsurface Compaction using Tension Infiltrometers

Abstract

Changes in soil physical properties due to compaction are a major concern in agricultural production and modeling of soil water movement and plant growth. The objectives of this study were to measure water infiltration under different compaction levels and to characterize the effects of compaction on the soil's porosity and its associated water-conducting properties. On a silt loam soil, relative to a control, four levels of subsurface compaction were induced: loosening and light, medium, and heavy compaction. Infiltration characteristics were measured in situ using tension infiltrometers. Near-saturated conductivities were calculated using Wooding's equation and further analyzed to derive the hydraulically effective macro-and mesoporosities and the flow-weighted mean pore radii. The data were also used for parameterization ofthe van Genuchten-Mualem model by inverse parameter estimation. A high susceptibility to the applied compaction was found: the saturated hydraulic conductivity of the heavily compacted soil was 81% less than that ofthe loosened soil. This soil property may be used as a proxy for compaction-induced changes in hydraulic characteristics. Increasing compaction also decreased the number of hydraulically effective macropores, reduced the flow-weighted mean pore radius, and the ttyj-parameter ofthe van Genuchten-Mualem model. Our findings give indirect evidence for two main efFects ofthe applied compaction.First, the reduced saturated hydraulic conductivity might be due to distortion of structural flow paths, reducing the connectivity and hydraulic effectiveness of many macropores. Second, compaction rearranged the pore space, resulting in more water-conducting mesopores.

Effects of tillage on the soil water retention curve during a fallow period of a semiarid dryland

“…As observed by Schwen et al (2011a, b) in a similar experiment, tillage operations had not a significant influence on n. This behavior could be due to the fact that the n parameter is more related to the soil texture (Jirku et al, 2013), while θ s and α are more associated to the soil structure. This hypothesis agrees with Schwen et al (2011c), who found that α was significantly affected by soil compaction. The increase of PSD max due to tillage operations (Fig.…”

Changes in the Structure of a Nigerian Soil under Different Land Management Practices

“…Analyses of h and r data showed that the average proportion of soil pores under the arable system can be grouped as 35, 28, and 37 % for transmission, storage, and residual pores, respectively; whereas for soils under the fallow system, these averages are 9, 18, and 73 % respectively. These results further reflect the comparative values of plant available water θ PAW , (i.e., storage pores) of both land management systems ( Figure 1d); and such changes in pore configuration place further restrictions on hydraulically effective (fluid conductivity) pores in fallow system soils (Kutílek, 2004;Schwen et al, 2011).…”

“…Land-management induced changes in PSDs demonstrate the ability of soil pores to hold water (Schwen et al, 2011). The change in porosity can be better appreciated when we look at pore size in a functional manner.…”

“…Changes in soil structure can be due to modification in soil aggregates or pores or both (Sasal et al, 2006). The soil pore system is critical to agriculture and the environment since it is the principal pathway for water and air transport in soils, and can be modified by land management practices (Schwen et al, 2011;Guedes et al, 2012). Therefore, understanding land management-induced changes that soil pore systems undergo becomes important for sound land use planning and management.…”

Near-saturated hydraulic conductivity measured on a swelling silty clay loam for three integrated weed management based cropping systems

“…Different studies suggest an increase of K(h) for clayey tilled soils shortly after tillage followed by a considerable decrease during winter and, finally, by an increase during spring/summer due to enhanced soil macroporosity (i.e., cracks, root development, earthworms channels) (Messing and Jarvis, 1993). These studies allowed identifying the key factors involved in the general temporal dynamics of K(h), such as initial soil water content (e.g., Das Gupta et al, 2006Zhou et al, 2008, porosity network (e.g., Buczko et al, 2006;Schwen et al, 2011b), crusting (e.g., Vandervaere et al, 1997Vandervaere et al, , 1998, crop and cropping periods (e.g., Castellini and Ventrella, 2012;Rienzner and Gandolfi, 2014) and tillage treatments (e.g., conventional tillage, reduced tillage, no-till) (e.g., Daraghmeh et al, 2008;Fuentes et al, 2004). However, less attention has been paid to the assessment of vertical variability compared to horizontal variability (Schwen et al, 2014).…”