Deep lime incorporation ameliorates the profile by reducing the activity of soluble Al, increasing soluble Ca and reducing resistance to root penetration by disturbing the hard, dense subsoil structure. Gypsum increases soluble Ca and reduces soluble Al and resistance to penetration by a mechanism not yet elucidated. The lack of movement of soluble Al down the profile in response to the gypsum front points to some type of precipitation mechanism such as the formation of alunite or basaluminite (Adams and Rawajfih, 1977). Conditions prevailing in this system appear to favor this possibility, which is being explored further. Treatments that brought about both chemical and physical amelioration resulted in yield increases.

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