ABSTRACT*

    The effects of chemicals applied to the soil through the irrigation system are more Intense than with standard roadcast applications. A review of literature indicated evidence for both the use of high quality, low eieitrical conductivity waters and the use of ammonium containing fertilizers as causes of soil clay dispersion, resulting in reductions in water permeability of the soil. Field trials compared urea ammonium nitrate and calcium nitrate applied at the rate of 20 pounds N per acre on the distance across the wetted area, soil ammonium levels, and soil electrical conductivity (ECe) levels on four sampling dates Hesults indicated that the soil had established an equilibrlum with the high quality irrigation water being used as indicated by soil ECe measureinents. Laboratory studies indicated that leaching with monovalent fertilizer salts resulted in a net loss of calcium from the soil and reduction irr solution permeability of as much as 900 percent.

*Bianchi, M.L. 1985. Effects of fertilizer and gypsum on soil water permeability. Masters Thesis, Library, California Polytechnic State University, San Luis Obispo.