“…This was demonstrated by Carminati and Vetterlein (2013) and Carminati et al (2010) who found that hydraulic conductivity and water uptake were enhanced by exudates after multiple cycles of wetting and drying. One driver is enhanced pore structure, which Reszkowska et al (2011) found helped to recover hydraulic conductivity of rhizosphere soil in a degraded pasture field under wet conditions. Exudates can therefore decrease plant water stress by regulating water content dynamics and aiding capture of water in the rhizosphere Ahmed et al 2014).…”
Background and aim Plant exudates greatly affect the physical behaviour of soil, but measurements of the impact of exudates on compression characteristics are missing. Our aim is to provide these data and explore how plant exudates may enhance the restructuring of compacted soils following cycles of wetting and drying. Methods Two soils were amended with Chia (Salvia hispanica) seed exudate at 5 concentrations, compacted in cores to 200 kPa stress (equivalent to tractor stress), equilibrated to −50 kPa matric potential, and then compacted to 600 kPa (equivalent to axial root stress) followed by 3 cycles of wetting and drying and recompression to 600 kPa at −50 kPa matric potential. Penetration resistance (PR), compression index (C C ) and pore characteristics were measured at various steps.
“…This was demonstrated by Carminati and Vetterlein (2013) and Carminati et al (2010) who found that hydraulic conductivity and water uptake were enhanced by exudates after multiple cycles of wetting and drying. One driver is enhanced pore structure, which Reszkowska et al (2011) found helped to recover hydraulic conductivity of rhizosphere soil in a degraded pasture field under wet conditions. Exudates can therefore decrease plant water stress by regulating water content dynamics and aiding capture of water in the rhizosphere Ahmed et al 2014).…”
Background and aim Plant exudates greatly affect the physical behaviour of soil, but measurements of the impact of exudates on compression characteristics are missing. Our aim is to provide these data and explore how plant exudates may enhance the restructuring of compacted soils following cycles of wetting and drying. Methods Two soils were amended with Chia (Salvia hispanica) seed exudate at 5 concentrations, compacted in cores to 200 kPa stress (equivalent to tractor stress), equilibrated to −50 kPa matric potential, and then compacted to 600 kPa (equivalent to axial root stress) followed by 3 cycles of wetting and drying and recompression to 600 kPa at −50 kPa matric potential. Penetration resistance (PR), compression index (C C ) and pore characteristics were measured at various steps.
“…On the other hand, animal trampling during grazing causes external stresses on the soil altering its structure and pore functions (Reszkowska et al, 2011). Thus, the physical quality of soils can be studied based on two concepts: the soil's physical resistance and its resilience (Gregory et al, 2009).…”
Section: A)mentioning
confidence: 99%
“…This is relevant in soils derived from volcanic ashes in southern Chile, since livestock production systems are based on pastures, which are grazed throughout the year, leaving the soil exposed to the effect of external pressures caused by grazing animals, and internal stresses due to wetting and drying cycles . While the first type of stress (animal trampling) can cause compaction, negatively affecting soil structure and its physical functions like hydraulic conductivity (Reszkowska et al, 2011), the internal stress allows the soil to recover its functions like air conductivity due to crack formation (Dörner et al, 2011.…”
Section: A)mentioning
confidence: 99%
“…Pore continuity was determined using two indexes of continuity proposed by Groenevelt et al (1984) and used by Dörner and Horn (2006) and Reszkowska et al (2011). These indexes are calculated from the relationship between air permeability (k a ) and air-filled porosity (� a ) and the relation between k a and a 2 .…”
Section: Evaluation Of the Porous System Before And After The Stressesmentioning
In southern Chile, different strategies have been utilized to improve the production levels of degraded pastures. Due to grazing, soils are subjected to mechanical and hydraulic stresses throughout the year. The aim of the study was to evaluate the effect of different strategies to improve a degraded naturalized pasture under sheep grazing on the resistance and resilience of the pore system of an Andisol subjected to mechanical and hydraulic stresses. Undisturbed soil samples were collected from two tilled, seeded and fertilized pastures (T1-T2), a non-tilled degraded and naturalized pasture with no fertilization (T3), a fertilized pasture (T4) and a non-tilledfertilized and ungrazed pasture (T5). Also, cylinders were filled with homogenized soil (T6). The tilled and non-tilled pastures (T1-T5) were able to maintain their functions of storage and transport of water and air as well as their mechanical properties against both stresses. No significant differences between the pasture improvement strategies were observed when evaluated during the second year after the implementation of the improvement strategies, which highlights the high resistance and resilience capacity of the Andisol. However, some tendencies (e.g. while the air capacity and permeability tended to increase following mechanical stress, plant available water increased; the opposite was observed following hydraulic stress) and significant differences (due to the simulated effect of aggregate destruction during tillage, a decrease in air capacity, and an increase in soil shrinkage capacity after compaction were assessed) were observed, which highlight the necessity for further studies to better understand the complex interactions in pasture systems.
“…Summarizing and integrating current knowledge and recent experimental findings Kölbl et al (2011, this issue) show that intensive grazing clearly decreased soil aggregation and the amount of fresh, litter-like particulate organic matter. As a consequence of weak aggregation in combination with animal trampling, soil organic matter mineralization is enhanced, whereas topsoil bulk densities were increased and infiltration rates, saturated hydraulic and air conductivities (Reszkowka et al, 2011, this issue) were found to be decreased. The effects of soil structure disruption due to grazing was further amplified by the degradation of vegetation patches and resulted in a texture controlled wettability of the soil surface (Kölbl et al, 2011, this issue).…”
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