Plant and Soil

, Volume 95, Issue 1, pp 135–147 | Cite as

Model experiments on the behaviour of roots at the interface between a tilled seed-bed and a compacted sub-soil

II. Entry of pea and wheat roots into sub-soil cracks
  • A. R. Dexter
Article
Received:
Revised:

Summary

Roots which grow down through a seed-bed and encounter a strong, untilled sub-soil beneath may be deflected horizontally. They will continue to grow horizontally along the top of the sub-soil either until the seed-bed dries out and the roots wilt and cease elongating, or until they find some path of low resistance down through the sub-soil. A major source of such paths is vertical cracks in the sub-soil.

Model experiments were done with artificial impenetrable sub-soils containing parallel cracks with widths in the range 0.5–3 mm. Roots of pea and wheat were grown down through beds of aggregates to encounter the artificial sub-soil at random positions. The roots were deflected horizontally until they encountered the vertical cracks. The proportions of roots which entered the cracks were found to decrease strongly with decreasing crack width and increasing (more perpendicular) angle of incidence between the root and the crack.

The experimental results were combined with the results from computer simulation studies which gave the proportions of roots encountering cracks at various angles with both hexagonal and parallel crack patterns. This showed that parallel crack patterns should enable a greater proportion of roots to enter the cracks than hexagonal crack patterns. Monocotyledonous plants which have several seminal root axes per plant have a statistical advantage over dicotyledonous plants which have only one seminal axis per plant with regard to crack entry.

Key words

Compaction pan Crack Hexagonal cracks Parallel cracks Pea Pisum sativum Root entry Triticum aestivum Wheat 
This is a preview of subscription content, log in to check access.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Dexter A R 1986 Model experiments on the behaviour of roots at the interface between a tilled seed-bed and a compacted sub-soil. I. Effects of seed-bed aggregate size and sub-soil strength on wheat roots. Plant and Soil 95, 123–133.Google Scholar
  2. 2.
    Edwards W M, Fehrenbacher J B and Vavra J P 1964 The effect of discrete ped density on corn root penetration in a planosol. Soil. Sci. Soc. Am. Proc. 28, 560–564.Google Scholar
  3. 3.
    Elkins C B, Thurlow D L and Hendrick J G 1983 Conservation tillage for long-term amelioration of plow pan soils. J. Soil and Water Cons., May–June, 305–307.Google Scholar
  4. 4.
    Fox W E 1964 Cracking characteristics and field capacity in a swelling soil. Soil Sci. 98, 413.Google Scholar
  5. 5.
    Hasegawa S, Thangaraj M and O'Toole J C 1985 Root behaviour: field and laboratory studies for rice and non-rice crops.In Proc. Int. Workshop on Physical Aspects of Soil Management in Rice-based Cropping Systems. Int. Rice Res. Inst., Los Baños, Philippines.Google Scholar
  6. 6.
    Heinonen R 1982 Alleviation of soil compaction by natural forces and cultural practices.In Proc. Int. Conf. Land Clearing and Development. Int. Inst. Tropical Ag., Ibadan, Nigeria.Google Scholar
  7. 7.
    Hoogmoed W B and Bouma J 1980 A simulation model for predicting infiltration into cracked clay soil. Soil Sci. Soc. Am. J. 44, 458–461.Google Scholar
  8. 8.
    Johnson W C 1962 Controlled soil cracking as a possible means of moisture conservation on wheat-lands of the South-Western Great Plains. Agron. J. 54, 323–325.Google Scholar
  9. 9.
    Lachenbruch A H 1961 Depth and spacing of tension cracks. J. Geophys. Res. 66, 4273–4392.Google Scholar
  10. 10.
    McGowan M, Wellings S R and Fry G J 1983 The structural improvement of damaged clay subsoils. J. Soil. Sci. 34, 233–248.Google Scholar
  11. 11.
    O'Callaghan J F and Loveday J 1973 Quantitative measurement of soil cracking patterns. Pattern Recognition 5, 83–98.CrossRefGoogle Scholar
  12. 12.
    Oades J M, Lewis D G and Norrish K 1981 Red-brown earths of Australia, Waite Agric. Res. Inst. and CSIRO, Adelaide.Google Scholar
  13. 13.
    Russell E W 1973 Soil Conditions and Plant Growth, Longman, London.Google Scholar
  14. 14.
    Sharma R B and Verma G P 1977 Characterization of shrinkage cracks in a medium black clay soil of Madhya Pradesh. I. Pattern and size of cracking in relation to vegetative covers. Plant and Soil 48, 323–333.CrossRefGoogle Scholar
  15. 15.
    Stefanelli G 1979 Tensioni interne, contrazioni, fessurazioni nei terreni argillosi per diminuzione di umidita. Revista di Ingegneria Agraria 9, 117–126.Google Scholar
  16. 16.
    van de Graaff R H 1978 Size of subsoil blocky peds in relation to textural parameters, depth and drainage.In Modification of Soil Structure. John Wiley, Chichester.Google Scholar
  17. 17.
    White E M 1966 Subsoil structure genesis: theoretical consideration. Soil Sci. 101, 135–141.Google Scholar
  18. 18.
    White E M 1967 Soil age and texture factors in subsoil structure genesis. Soil Sci. 103, 288–298.Google Scholar
  19. 19.
    Whiteley G M and Dexter A R 1981 Elastic response of the roots of field crops. Physiol. Plant. 51, 407–417.Google Scholar
  20. 20.
    Whiteley G M and Dexter A R 1982 Root development and growth of oilseed, wheat and pea crops on tilled and non-tilled soil. Soil and Tillage Res. 2, 379–393.Google Scholar
  21. 21.
    Whiteley G M and Dexter A R 1983 Behaviour of roots in cracks between soil peds. Plant and Soil 74, 153–162.CrossRefGoogle Scholar

Copyright information

© Martinus Nijhoff Publishers 1986

Authors and Affiliations

  • A. R. Dexter
    • 1
  1. 1.Department of Soil Science, Waite Agricultural Research InstituteThe University of AdelaideGlen OsmondSouth Australia

Personalised recommendations