Plant and Soil

, Volume 149, Issue 1, pp 129–139 | Cite as

Root elongation of seedling peas through layered soil of different penetration resistances

  • A. G. Bengough
  • I. M. Young
Research Article


Field soils contain localized zones of larger penetration resistance within peds and compacted layers, while cracks and biopores offer low resistance pathways to roots. Root responses to such localized conditions have not been investigated in detail. This study examined what happens to the root elongation rate when roots grew through a layer of hard soil into a layer of looser soil for a 4 day period.

The experiment was performed twice; firstly with the shoot in continuous darkness, and secondly with it exposed to a day-night cycle to prevent etiolation of the shoot. Pea seedlings were grown in columns of a sandy loam soil which was packed to bulk densities of 0.85, 1.1, 1.3 or 1.4 Mg/m3 in the top layer and 0.85 Mg/m3 in the bottom layer.

The root elongation rate in the top layer of 1.4 Mg/m3 soil (penetrometer resistance=1.8 MPa) was only 55% of the elongation rate in the top layer of 0.85 Mg/m3 soil (penetrometer resistance=0.06 MPa). The elongation rate of roots that had grown through the top layer of 1.4 Mg/m3 soil into the bottom layer of loose soil was reduced by some residual effect of the mechanical impedance. The root elongation rate in the bottom layer of loose soil decreased as the penetrometer resistance of the top layer of soil increased. The daily elongation rate of the roots in the bottom layer that had grown through the 1.4 Mg/m3 soil averaged only about 65% of the elongation rate of the roots that had grown through the 0.85 Mg/m3 soil.

This residual effect of mechanical impedance on root elongation persisted for at least 2 days and was more severe in the day-night cycle experiment than in the dark experiment. These results have important implications for modelling root elongation in any soil in which the soil strength changes with distance or with time.

Key words

compaction mechanical impedance penetrometer Pisum sativum root diameter sandy loam shoot elongation soil strength 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Barley K P 1962 The effects of mechanical stress on the growth of roots. J. Exp. Bot. 13, 95–110.Google Scholar
  2. Barley K P 1963 Influence of soil strength on growth of roots. Soil Sci 96, 175–180.Google Scholar
  3. Barley K P 1965 The effect of localized pressure on the growth of the maize radicle. Aust J. Biol. Sci. 18, 499–503.Google Scholar
  4. Bengough A G and Mullins C E 1990 Mechanical impedance to root growth: A review of experimental techniques and root growth responses. J. Soil Sci. 41, 341–358.CrossRefGoogle Scholar
  5. Bengough A G and Mullins C E 1991 Penetrometer resistance, root penetration resistance and root elongation rate in two sandy loam soils. Plant and Soil 131, 59–66.Google Scholar
  6. Dexter A R 1978 A Stochastic model for the growth of roots in tilled soils. J. Soil Sci. 29, 102–116.Google Scholar
  7. Eavis B W 1967 Mechanical impedance to root growth. Ag. Eng. Symp., Silsoe. Paper 4/F/39, 1–11.Google Scholar
  8. Greacen E L 1986 Root response to soil mechanical properties. Trans. 13th Int. Cong. Soil Sci. 5, 20–47.Google Scholar
  9. Goss M J 1977 Effects of mechanical impedance on root growth in barley (Hordeum vulgare L.). I. Effects on elongation and branching of seminal roots. J. Exp. Bot. 28, 96–111.Google Scholar
  10. Goss M J and Russell R S 1980 Effects of mechanical impedance on root growth in barley (Hordeum vulgare L.). III. Observations on the mechanism of response. J. Exp. Bot. 31, 577–588.Google Scholar
  11. Jakobsen B F and Dexter A R 1987 Effect of soil structure on wheat root growth, water uptake and grain yield: A computer simulation model. Soil Till. Res. 10, 331–345.CrossRefGoogle Scholar
  12. Masle J and Passioura J B 1987 The effect of soil strength on the growth of young wheat plants. Aust. J. Plant Physiol. 14, 643–656.CrossRefGoogle Scholar
  13. Passioura J B and Gardner P A 1990 Control of leaf expansion in wheat seedlings growing in drying soil. Aust. J. Soil Sci. 17, 149–157.Google Scholar
  14. Sarquis J I, Jordan W R and Morgan P W 1991 Ethylene evolution from maize (Zea mays L.) seedling roots and shoots in response to mechanical impedance. Plant Physiol. 96, 1171–1177.PubMedCrossRefGoogle Scholar
  15. Taylor H M and Ratliff L F 1969 Root elongation rates of cotton and peanuts as a function of soil strength and water content. Soil Sci. 108, 113–119.Google Scholar
  16. Voorhees W B, Farrell D A and Larson W E 1975 Soil strength and aeration effects on root elongation. Soil Sci. Soc. Am. Proc. 39, 948–953.CrossRefGoogle Scholar
  17. Yorke J S and Sagar G R 1970 Distribution of secondary root growth potential in the root system of Pisum sativum. Can. J. Bot. 48, 699–704.Google Scholar

Copyright information

© Kluwer Academic Publishers 1993

Authors and Affiliations

  • A. G. Bengough
    • 1
  • I. M. Young
    • 1
  1. 1.Soil-Plant Dynamics Group, Department of Cellular and Environmental PhysiologyScottish Crop Research InstituteDundeeUK

Personalised recommendations