The objective of this study was to determine the correlation between potentiometric surface and the depth to selected soil morphological indicators of wetness for the Glynwood (Aquic Hapludalf), Blount (Aeric Epiaqulaf), and Pewamo (Typic Argiaguoll) soils in Delaware County, Indiana. Four years of potentiometric surface measurements were averaged and compared to detailed soil descriptions performed by the Natural Resources Conservation Service. Significant correlations exist between the morphological indicators and the potentiometric surface for the Glynwood (moderately well drained) 2-m depth piezometers and 2-m depth slotted pipes, the Blount (somewhat poorly drained) top of the C horizon and 2-m depth piezometers, and the Pewamo (poorly drained) top of the B horizon piezometers. The relationships among the horizons in which potentiometric surface correlated to indicator depth may be a function of the increased persistence and shallowness of the potentiometric surface in mid-April. / Department of Natural Resources and Environmental Management

A field lysimeter experiment was conducted on a sandy loam soil during the growing seasons of 1989 and 1990. The experiment tested the effects of four water table treatments on soybean (Glycine max) yields. The water table depths were 40, 60, 80, and 100 cm in depth. / Yields were measured in terms of: total seed mass per plant, number of seeds per plant, number of pods per plant, number of seeds per pod, and speed protein content at harvest. / The water management simulation model DRAINMOD, was used to develop irrigation and drainage strategies for soybean production. Three water table management methods were tested with each of three water table depths. The methods were conventional drainage, controlled drainage, and subirrigation, and the water table depths were 40, 60, 80, and 100 cm. / It was shown that for the driest year highest yields are obtained with subsurface irrigation and a weir setting of 40 cm. For the average year, highest yields are obtained with subirrigation and a 60 cm weir setting. For the wet years, best results are found when controlled drainage is used with 80 cm weir setting. It was found that in all but the driest and wettest years controlled drainage improved yields by 10% or more.

Thesis (M.S.)--University of Nevada, Reno, 2004. / "December, 2004." Includes bibliographical references (leaves 79-83). Online version available on the World Wide Web.

Thesis(M.S.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references.

Thesis (Ph.D.) --Murdoch University, 2004. / Thesis submitted to the Division of Science and Engineering. Includes bibliographical references (leaves R-1 - R-24). Also available via the World Wide Web at.

Thesis (M.S.)--Oregon State University, 1998. / Typescript (photocopy). Includes bibliographical references (leaves 129-135). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1993. / Typescript (photocopy). Includes bibliographical references (leaves 98-105). Also available on the World Wide Web.

Thesis (M.S.)--Brigham Young University. Dept. of Geological Sciences, 2007. / Includes bibliographical references (p. 38-41).

Water table control by subsurface drainage has been shown to affect leaching losses of nitrate-nitrogen: a concern both for economic use of fertilizer, and for maintenance of water quality. The effect of water table height on leaching of NO₃⁻-N was investigated in this study in nineteen 15cm x 100cm undisturbed cores of silty clay loam. The experiment simulated fertilization followed by rainfall, then rapid water table rise and fall, under conditions similiar to those experienced in the early spring in the Lower Fraser Valley. In the first part of the experiment, a concentrated solution of KNO₃ and KG (equivalent to 35 kg/ha of N and 22 kg/ha of Cl) was applied to the columns, followed by intermittent leaching with distilled water. Leachate from two depths in each column was collected before and after a period of static water table, and analyzed for NO₃⁻, No₂⁻, NH₄⁺, and Cl⁻. This procedure was repeated without nutrient addition in the second part of the experiment. Chloride was used an inert tracer to follow anion movement and retention within the columns. There was no significant difference in the leachate NO₃⁻ concentration or leachate N/CI ratio from any of the four water table heights tested (15, 35, 55, and 75 cm above drain depth). The NO₃⁻ concentrations and N/CI ratios decreased with depth in the soil columns, indicating removal of N from the percolating soil solution, either by denitrification or immobilization. The variability in leachate concentrations among all columns was very high (eg. for a typical sample time, NO₃⁻-N ranged from 0.01 to 15.72 mg/L, and Cl⁻ ranged from 4.8 to 14.5 mg/L), as was the variability in constant head satiated hydraulic conductivities (range: 1 to 1468 cm/day; CV = 181%), and drainable porosity (range: 2.7 to 10.4%; CV = 39%). Cross sections of columns leached with 1% methylene blue solution did not reveal differences in patterns of water transmission between low and high conductivity columns. Indications were that penetration of dye was greater in columns with higher conductivities, and that preferential flow occurred in all columns examined. Leachate concentrations and N/CI ratios correlated significantly with hydraulic conductivity: Spearman's correlation coefficients were always > 0.8 for samples obtained from the bottom of the columns. However, even when the conductivity was included as a covariate in an analysis of covariance, there was no significant effect of water table height on nitrate leaching. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

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