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This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

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Important pedogenic processes of soils formed on dolomitic limestones are affected by the degree of in-situ weathering of the underlying bedrock. Decalcification and silicate clay illuviation of Haplustalfs and Calciustolls of the Colorado Plateau in northwestern Arizona results from the establishment of effective porosity in the parent rock. The underlying carbonate strata, the Kaibab Formation, are a complex limestone-dolomite-chert marine sediment of Permian age. Diagenetic processes have modified the initial porosity present at the time the sediment was deposited. Pleistocene meteoric waters, percolating downward, have resulted in the solutioning and partial removal of the calcium carbonate and the establishment of a porous dolomitic framework. Under these conditions, soils forming in residuum are able to decalcify and to form argillic horizons. However, in more resistant limestones, compaction during burial has resulted in a nonporous micrite which retards calcite removal by meteoric waters. Under these conditions, soil profiles maintain a high CaCO₃ content and silicate clay illuviation does not occur. Micaceous clay minerals of residual origin are converted to montmorillonite in the Alfisols. A probable sequence of events for this transformation to occur is: (1) the removal of calcite from the dolomitic limestone bedrock and the formation of a dolomitic framework, (2) the slow dissolution of dolomite and release of Mg⁺⁺ into solution, (3) the incorporation of Mg⁺⁺ into the octahedral layer of the mica and the release of K⁺ from the mica interlayer position, and (4) the illuviation of montmorillonite to form the argillic horizon. Eolian dust is also important to soil genesis on the Colorado Plateau. In particular, quartz in the coarse silt fraction (31-44 um) and quartz and biotite in the very fine and fine silt fractions (2.0-16 um). Two alluvial soils of Pleistocene age shows important morphological differences. Thick carbonate accumulations of ground water origin are present in the older soil. The effects of the Pleistocene-Holocene climatic change on this area are: (1) modification of karst topographic features, (2) aggradation of valley bottoms, and (3) the influence of Holocene slope wash Pleistocene soil properties such as calcite, dolomite and organic matter.

Selected components of the water and energy balances at the surface of a bare clay loam were measured at 57 locations in a 1 ha field. Spatial and temporal variability of these components were also studied. Components included evaporation, irrigation, moisture storage, sensible heat flux and long wave radiation. Sub-studies were conducted on irrigation uniformity under low pressure sprinklers; and, on steel versus plastic microlysimeters (ML) of various lengths. An energy balance model of evaporation, requiring minimal inputs, was developed and validated giving an r$\sp2$ value of 0.78. Model improvements included an easy method of accurately estimating soil surface temperature at many points in a field, and an empirically fitted transfer coefficient function for the sensible heat flux from the reference dry soil. The omission of soil heat flux and reflected shortwave radiation terms was shown to reduce model accuracy. Steel ML underestimated cumulative evaporation compared to plastic ML at 20 and 30 cm lengths. Cumulative evaporation increased with ML length. The 10 and 20 cm ML were too short for use over multiple days but 30 cm ML may not be long enough for extended periods. Daily net soil heat flux for steel ML averaged 44% higher than that for both plastic ML and undisturbed field soil. Christiansen's uniformity coefficient (UCC) was close to 0.83 for each of 3 irrigations when measured by both catch cans and by profile water contents. But UCC for the change in storage due to irrigation averaged only 0.43 indicating than the high uniformity of profile water contents was more due to surface and subsurface redistribution than to the uniformity of application. Profile water contents and catch can depths were time invariant across at least 3 irrigations. Midday soil surface temperatures and daily evaporation were somewhat less time invariant. Variogram plots for evaporation and surface temperature showed mostly random behavior. Relative variograms represented well the spatial variability of both catch can depths and profile water contents. A strong link was demonstrated between the time invariance of a variable and the usefulness of kriging on that variable.

Field and laboratory experiments to determine the effect of the quality of irrigation water and the combination effects of the quality of water and chemical amendments (Gypsum and H ₂SO₄) on growth and yields of sudangrass, total soluble salt and ionic distribution and the infiltration rates of a Pima soil were conducted. Pima soil was classified as calcareous saline-sodic soil. A field experiment was conducted on the University of Arizona Experimental Farm at Safford, Arizona, for a period of five years. During the first three years, three qualities of water as supplied by well, river and city were used. During the last two years, these waters were coupled with two chemical amendments, gypsum and sulfuric acid. The experiment was a randomized split plot design with nine main plots and 27 subplots and three replications. The rates of the amendments were arbitrarily chosen 1 and 1.72 ton/acre of H ₂SO₄ and gypsum respectively. Four harvests were made over the two-year period and city water treatment gave the best growth and yield of sudangrass as compared to well and river water treatments. H ₂SO₄ and gypsum increased the yield significantly in comparison to the control in 1975. No significant effects of the chemical amendments on the growth and yield of sudangrass were obtained in 1976. Significant negative correlations between the EC and ESP of the first two feet of soil and yield of sudangrass were obtained. Soil analysis indicated that significant decrease in the pH and ESP of the soil resulted from H ₂SO₄ application with the three water treatments. Gypsum reduced pH and ESP significantly just with well water treatment. Due to the stratified texture of soil profile, ions and salts accumulated in the center of the sampled profile. Infiltration rates were higher for well water treatments than for city water treatments. H ₂SO₄ increased the infiltration rates significantly with all water treatments; gypsum increased infiltration only with well water treatment. Infiltration was further studied in the laboratory using soil columns. Two rates of acid and two rates of gypsum were used (1 or 5 and 1.72 or 8.6 ton/acre H ₂SO₄ and gypsum respectively). The higher rate of H ₂SO₄ gave the highest infiltration rate and the lowest infiltration rates were obtained with control with all water treatments. The low rate of H ₂SO₄ and the high rate of gypsum gave similar infiltration rates with the three water treatments. Gypsum treated soil columns required more water to be leached to a specific EC than H ₂SO₄ treated and control columns. More salt can be removed from the soil per unit volume of water with H ₂SO₄ treatment than gypsum or untreated soil. The poorest quality of irrigation water required the least time and amount of water needed to reach equilibrium between the solid and solution phases of soil. The EC of effluent was found to be an index to predict the presence of gypsum and lime in the soil under very low water penetration. Regression equations were developed to predict the time and depth of water required to leach one foot of Pima soil column to a specific EC with a given quality of water and a given type and rate of chemical amendments (H ₂SO₄ and gypsum). A regression equation was developed to estimate the EC of the saturation extract from that of 1:1 soil :water ratio for Pima soil.

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