FACTORS INFLUENCING THE SOIL PENETRATION RESISTANCE OF SOME VERTISOLS IN EGYPT.

The current study aims to determine the soil penetration resistance of some
Vertisols as well as to study the main contributing soil factors. Investigation of
undisturoed sou samples, of eighteen profiles represent the Vertisols in E~ypt,
showed that the soil penetration resistance ranges between 11.3 and 45.6 N/cm , as
affected by different soil constituents and characteristics. The monovariant analysis
reveals that clay content, water stable aggregates, total carbonates and organic
matter contents are positively correlated with the soil penetration resistance.
Whereas, the total soluble salts is negatively and non-significantly correlated to soil
penetration resistance. However, none of the simple linear regression equations could
represent this relationship or predict soil resistance values for given values of the soil
factors. The multivariate analysis results in very highly significant multiple linear
regression equation with high correlation coefficient, meaning that the computed
equation could represent the relationship between soil penetration resistance and soil
constituents and characteristics under consideration. The partial correlation analysis
shows that water stable aggregates, clay content and total carbonates are the most
effective soil factors on the soil penetration resistance and are followed by organic
matter content and total soluble salts. As a conclusion, the soil penetration resistance
is not a function of one soil factor but several factors.