Shrinkage of Bare and Cultivated Soil

Abstract

The surface subsidence of shrink‐swell soils may be used to estimate the soil profile water content and soil behaving. Roots are known to affect cracking patterns by anchoring the soil mass, thus influencing soil shrinkage. Our hypothesis was that plant roots will influence soil shrinkage measured by vertical surface subsidence. We tested this hypothesis by measuring shrinkage in a large weighing lysimeter for bare soil with no root system and for soils under wheat (Triticum turgidum L.) and alfalfa (Medicago sativa L.) crops possessing fibrous and tap root systems, respectively. The volume‐loss shrinkage curves for both bare and cultivated soil were found to conform to the straight‐lines model, with distinct changes in shrinkage zones, in spite of uneven water‐content distributions in the profile. The shrinkage characteristic (i.e., the differential change in bulk volume divided by the change in volume water) was greater for fallow (0.677) than for wheat (0.380) and alfalfa (0.377), with the cultivated conditions being similar. These data suggest that plant roots may have large effects on in situ soil shrinkage rates and the water‐content zones throughout which they occur. This result means that a soil's shrinkage characteristic may change depending on the cropping condition. It also means that shrinkage measurements from soils without rooting systems (e.g., small cores or clods) are not necessarily representative of actual shrinkage properties observed in the field.

Numerical analysis of crack generation in saturated deformable soil under row-planted vegetation

“…Fox (1964) found that the formation of inter-row cracks could be attributed to the anchoring of soil to the roots of the crops. Sharma and Verma (1977), Mitchell and van Genuchten (1992), and Dasog and Shashidhara (1993) provide supplementary explanations of the effect of vegetation on crack formation. These studies suggest that both anchoring of soil to roots and bidirectional water movement caused by the spread of roots under the rows affect the generation of inter-row cracks.…”

Effects of cropping and puddling practices on the cracking patterns in paddy fields

“…Fox (1964) reported that the formation of inter-row cracks could be attributed to the anchoring of soil by the roots of the crops. Sharma and Verma (1977) and Mitchell and van Genuchten (1992) also provided supplementary explanations for the formation of cracks between rows. In a laboratory experiment, Yoshida et al (2001) observed that bidirectional water movement occurring between rows of crops could lead to the formation of inter-row cracks.…”

Soil water characteristic curve measurement without bulk density changes and its implications in the estimation of soil hydraulic properties

“…2. Although, the slope of the basic zone is not necessary equal to 1 Braudeau et al, 1999;Braudeau et al, 2005;Mitchell and van Genuchten, 1992) and may be occasionally higher than 1 (Boivin et al, 2006a;Boivin et al, 2006b;, the type of larger slope obtained here, as shown in Fig. 3, was quite exceptional.…”