During transient‐state infiltration of steady, low intensity rain into laboratory soil columns, moisture contents at increasing soil depths tended with time to approach a constant level. This level, as well as the observed rates of wetting‐front advance, were higher in cases of more intense rain. For the conditions studied, soil moisture contents and wetting‐front advance rates associated with ponded‐water infiltration were generally considerably higher than those of rain infiltration profiles. The differences between the observed and the theoretically predicted rain infiltration profile data were insignificant for rains of low intensity but significant for those of higher intensity. The wetting front advance observations confirmed certain aspects of the theory presented in part I of this paper.

A technique of utilizing surface runoff from microcatchments was adapted to grow pasture shrubs (Atriplex halimus L.) on a barren saline loessial plain in the desert. The average annual rainfall of the region is about 90 mm. Microcatchments varied in size from 16 m2 to 1,000 m2. Maximum yields were obtained from a 32 m2 microcatchment which produced an average annual yield of 160 feed units/ha/yr, as compared to 5 to 10 feed units/ha, on the untreated plain. Protein yield was about 40 kg/ha. The system costs $5 to 20 per ha to construct and can repay its construction cost within 2 to 3 years. The method is also being adapted to the growing of fruit trees.

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The yield of peanuts (Arachis hypogaea) grown in artificially salinized plots was reduced to 50% at ECe of 4.7 mmhos/cm and by 20% at ECe of 3.8 mmhos/cm. Yield reduction was the same for equal mean soil salinities regardless of the shape of the soil salinity profile. Reduction in water uptake as a result of increased soil salinities was probably the consequence rather than the cause of the reduced growth. The salt tolerance during germination was much higher than during subsequent growth. A 50% reduction in germination was obtained at ECe of 13 mhos/cm and in seedling development at ECe, of 7.2 mmhos/cm.

Different types of solutions of the differential equation describing the process of cation exchange chromatography are compared and evaluated for their applicability to soil conditions. In cases where divalent cations replace monovalent ions, the exchange front assumes a stationary profile at an early stage which then yields an analytical solution provided a fairly simple exchange equation like that of Gapon or Vanselow is applicable. Where monovalent ions replace divalent ions, a non-stationary front arises, which is strongly dominated by the exchange equation. A good approximation of the front can be obtained by an analytical solution taking no account of diffusion or dispersion. Knowledge of the total electrolyte in the soil column is often the limiting factor in predicting the location and shape of the exchange front.[112.23.07]. (Abstract retrieved from CAB Abstracts by CABI’s permission)