Laboratory studies of crust development in irish and iraqi soils

Thirty soils differing widely in origin, texture and organic carbon content were used to study crust properties and development under laboratory conditions. Crust strength was measured as penetration resistance to an upward moving probe both with and without artificial rain treatment. The patterns of penetration resistance with time of drying under infra-red lamps varied considerably, the time taken to reach maximum and steady values for penetration resistance varying from 4 to 10 days. Maximum penetration resistance values ranged from approximately 50 to 500 kPa with one Iraqi soil recording a value of 800 kPa. The soils separated into 3 fairly distinct groups when penetration resistance was plotted against moisture content: Group I showed a sudden and sharp increase, Group II a gradual increase, whereas Group III did not show a definite relationship. A positive linear relationship was found between maximum penetration-resistance values of soils with and without artificial rain treatment. There was also a high positive correlation between small (2−0.53 mm) water-stable aggregates and penetration resistance and a negative correlation between penetration resistance and percentage water-stable aggregates of > 2 mm in size. In seedling emergence trials with spring barley (Hordeum vulgare L.), maximum emergence (90–98%) was recorded at penetration resistance (no rain treatment) of 75–110 kPa and zero emergence at approximately 300 kPa, with a good negative relationship between these values. There was a positive relationship between seedling emergence and penetration resistance values < 75 kPa, failure to emerge being due to a lack of anchorage and radial support for the shoot. Simulated rain treatment, which led to additional crust strength, reduced seedling emergence further for the limited number of soils tested.

[1]  W. C. Moldenhauer.  Influence of rainfall energy on soil loss and infiltration rates : II. Effect of clod size distribution. , 1970 .

[2]  M. F. O'sullivan,et al.  Soil strength and crop emergence in direct drilled and ploughed cereal seedbeds in seven field experiments , 1982 .

[3]  E. Stibbe,et al.  Soil Crusting and Emergence of Wheat Seedlings1 , 1977 .

[4]  B. P. Ghildyal,et al.  Effect of surface crusting on emergence of soybean (Glycine max L. Merr) seedlings II. Influence of tillage treatment, planting method and time of crust formation , 1983 .

[5]  H. M. Taylor,et al.  Soil Strength and Seedling Emergence Relations. I. Soil Type, Moisture Tension, Temperature, and Planting Depth Effects1 , 1965 .

[6]  L. A. Richards.  Modulus of Rupture as an Index of Crusting of Soil1 , 1953 .

[7]  L. E. Allison.  Soil and Plant Responses to VAMA and HPAN Soil Conditioners in the Presence of High Exchangeable Sodium1 , 1956 .

[8]  W Arndt,et al.  The nature of the mechanical impedance to seedlings by soil surface seals , 1965 .

[9]  K. Barley,et al.  Mechanical Resistance as a Soil Factor Influencing the Growth of Roots and Underground Shoots , 1967 .

[10]  K. Brown,et al.  Evaluation of simulated seedling emergence through rainfall-induced soil crusts , 1974 .

[11]  R. J. Hanks,et al.  Seedling Emergence of Wheat, Grain Sorghum, and Soybeans as Influenced by Soil Crust Strength and Moisture Content , 1957 .

[12]  W. D. Kemper,et al.  Irrigation Method as a Determinant of Large Pore Persistence and Crust Strength of Cultivated Soils1 , 1975 .

[13]  Sheila M. Royle,et al.  Soil Impedance and Field Emergence in Calabrese , 1977 .

[14]  E. Epstein,et al.  Soil Losses and Crust Formation as Related to Some Soil Physical Properties 1 , 1967 .

[15]  Howard M. Taylor,et al.  SOIL STRENGTH‐ROOT PENETRATION RELATIONS FOR MEDIUM- TO COARSE‐TEXTURED SOIL MATERIALS , 1966 .