Responses of Biopore Channels from Roots to Compression by Vertical Stresses

Abstract

The channels created in soil by roots and soil animals (biopores) play an important role in the subsequent movement of water, air, and new roots through irrigated clay soils in southeastern Australia. The maintenance of these biopores is critical for both crop productivity and erosion control. If these biopores are to remain open, they must be able to withstand the vertical stresses associated with vehicle and animal traffic. This study had three aims: (i) to examine the influence on porosity and permeability of naturally occurring channels, (ii) to determine the magnitude of vertical stresses that artificially created channels could withstand, (iii) to test the effect of channel angle to the direction of the stress. Air‐filled porosity of soil cores at −10 J/kg was decreased in a linear fashion as the applied stress was increased from 50 to 400 kPa. The reduction in air‐filled porosity was relatively independent of the size or the presence of biopores. However, the intrinsic permeability of the soil cores to air was positively correlated with the diameter of the biopores, and the permeability was little affected by applied stresses up to 200 kPa if the initial diameter of the biopores was >3.5 mm. The resistance of the channels to stresses was greatest if the vertical stress was parallel to the axis of the channels. Agricultural practices on these soils should not only encourage formation of biopores, but should also minimize stresses >200 kPa to the subsoil so that these biopores can remain open.

Infiltration Rate of a Sandy Loam Soil: Effects of Traffic, Tillage, and Plant Roots

“…The minimum or no tillage plus the extensive tap-root system of the alfalfa would have promoted and protected the macropores, which would conduct water even in compacted soil. Blackwell et al (1990) demonstrated that biopore channels formed by alfalfa roots can be very stable at diameters >4 mm under stresses up to 200 kPa.…”

Influence of time and method of alfalfa stand termination on yield, seed quality, N uptake, soil properties and greenhouse gas emissions under different N fertility regimes

“…In a rotation, alfalfa reduces the input of N fertilizer for the succeeding annual crops while also improving seed yield and protein content (Badaruddin and Meyer 1990;Zentner et al 1990Zentner et al , 2001Entz et al 1995;Mohr et al 1999). It also helps to reduce soil salinity (Agriculture Canada 1991), soil erosion (Stinner and House 1989) and weed populations (Dryden et al 1983;Harvey and McNevin 1990), and improve soil moisture by snow trapping (Cutforth et al 2002), improving physical properties (Blackwell et al 1990) and organic matter . However, after about 3 years, the productivity of alfalfa stands tends to decline and the stands are terminated.…”

Soil and macro-pores under uniaxial compression. I. Mechanical stability of repacked soil and deformation of different types of macro-pores

“…Soils restored from excavation material which was temporarily removed, for example during gravel exploitation, are particularly susceptible to compaction, as excavation, transport and repacking disrupt their structure and destabilize them (Lebert and Springob, 1994). Impacts on the macro-pores are of particular concern, as these structures play a crucial role for many soil processes such as drainage or aeration (Blackwell et al, 1990;Allaire-Leung et al, 2000).…”