A study was conducted to determine relationships among physical, mineralogical, and soil hydraulic properties of Ultisols developed in unconsolidated sediments of the Lower Coastal Plain. Soil water retention curves, saturated hydraulic conductivity, bulk density, quantitative mineralogy, surface area, and particle size distribution were determined by horizon for seven pedons and relationships among them were analyzed by regression analysis procedures. Fine sand, sand and clay percentages were highly correlated with saturated hydraulic conductivity, surface area and volumetric water contents at specific pressure heads. Correlation coefficients > 0.95 were obtained for regression equations estimating soil water retention curves from particle size data. These relationships can be useful for quick characterization of soil hydraulic properties from particle size distribution data. No significant correlations were found between soil hydraulic and mineralogical properties of the clay fraction.

Imazaquin {2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid} sorption and mobility were studied in five Alabama soils ranging from sandy loam to clay. Techniques included thinlayer soil chromatography, batch equilibrium, and soil solution recovery. Imazaquin was mobile in all soils with Rfvalues of 0.8 to 0.9. Sorption based on batch equilibrium was minimal with Kdvalues ranging from 0.001 to 0.21. The soil solution recovery technique was used to evaluate imazaquin sorption in each soil as influenced by imazaquin concentration, wetting and drying, and pH. As herbicide concentration added to the soils was increased from 0.1 to 10 mg/kg, the amount of14C-imazaquin in soil solution increased. Temporarily drying each soil to 25 or 50% of field capacity resulted in maximum sorption of imazaquin. Lowering the pH enhanced sorption in all soils such that the amount of imazaquin in solution ranged from 38 (low pH) to 100% (high pH). Soil sorption appeared to be governed by the pH-dependent charge surfaces from aluminum and iron oxyhydroxides (specifically hematite and gibbsite) and kaolinite.

Soil cores were taken from each of three, 2‐, 23‐, and 52‐yr‐old research ponds (650–1,010 m2 area) at Auburn, Alabama. Many physical and chemical variables changed in intensity with increasing depth in cores. Compared to original compacted pond soil, sediment contained more moisture; had lower bulk density (<1.4 g/cm3); possessed higher percentages of silt and clay; had greater porosity, specific surface area, and cation exchange capacity; and contained greater concentrations of organic matter and nutrients. Sediment organic matter was highly decomposed as evidenced by low proportions (5–15%) of carbon and nitrogen associated with the light fraction (soil retained on a 53‐μm sieve). Sediment depth at 100‐cm water depth increased with pond age (11.7 cm, 28.3 cm, and 48.3 cm in 2‐, 23‐, and 52‐yr‐old ponds, respectively), but sediment composition did not change greatly over time. Successive layers in cores were as follows: 1) water near the soil‐water interface with a high concentration of solids; 2) high moisture content sediment with dry bulk density <0.3 g/cm3; 3) lower moisture content sediment with bulk density between 0.3 and 0.5–0.7 g/cm3; 4) rapid transition of bulk density from 0.5–0.7 g/cm3 to 1.4 g/cm3; 5) original compacted soil with bulk density of 1.4–1.7 g/cm3. We propose that these five layers be referred to as F (flocculent layer), S (stirred or mixed sediment), M (mature, bulk, un‐mixed sediment), T (transitional layer), and P (original, undisturbed pond bottom) horizons, respectively. Superficial, oxidized sediment is termed an So horizon, and the reduced part of the S horizon is termed an Sr horizon. The upper part of the T horizon is an MT horizon when it is similar to the M horizon, or a FT horizon when it resembles the P horizon. A system for delineating horizons in pond soil profiles will be valuable in future attempts to classify pond soils.

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Mobility and sorption of radiolabeled sulfometuron {2-[[[[(4,6-dimethyl-2-pyrimidinyl)amino] carbonyl] amino] sulfonyl] benzoic acid} and imazapyr {(±)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-pyridinecarboxylic acid} were evaluated in five soils representative of the major soil types in Alabama. Thin-layer soil chromatography indicated that sulfometuron was slightly more mobile (average Rf= 0.86) than imazapyr (average Rf= 0.79). Sulfometuron was more subject to sorption (average kd= 0.29) than imazapyr (average kd= 0.09) in batch equilibrium experiments. Least sorption of both herbicides occurred on clay soils, and maximum sorption occurred on a sandy clay. Similar results were obtained with a soil solution recovery technique. Sorption of both herbicides was exhanced by temporary reduction in soil water content and by lowering soil pH. The pH response of imazapyr was greater than that of sulfometuron.

Soil thin-layer chromatography and a soil solution technique were used to evaluate chlorimuron adsorption and mobility in five Alabama soils. The order of adsorption was atrazine > metribuzin > chlorimuron; mobility was chlorimuron > metribuzin > atrazine. The order of adsorption of chlorimuron in the five soils was Sumter clay > Eutaw clay > Lucedale fine sandy loam > Decatur silt loam > Dothan sandy loam, and Rfvalues were 0.63, 0.73, 0.69, 0.76, and 0.80, respectively. Chlorimuron mobility and adsorption were not highly correlated to any one soil type. Adsorption of all herbicides was inversely related to soil pH. Maximum chlorimuron adsorption in the Hiwassee loam was attributed to the high hematite and gibbsite content of the soil.

Analyses of bottom soils from three recently-established (newer) and three older ponds on each of two, semi-intensive shrimp farms near Choluteca, Honduras, revealed that the 0 to 2.5 cm layer had greater concentrations of most variables than deeper layers. Concentrations of total carbon, nitrogen, sulphur, phosphorus, calcium, iron, manganese, and zinc were greater in older than in newer ponds on one or the other of the farms. After 8-11 y of continuous production, total carbon concentrations varied over pond bottoms, and concentrations usually were greatest (1.5-2.5%) in inlet sections. Nitrogen concentrations were about 20% those of carbon and changes in nitrogen concentration closely followed those of carbon. Precipitation of iron pyrite (FeSz) in anaerobic soil layers was the apparent cause of sulphur accumulation in older ponds. Phosphorus accumulated in older ponds on the farm where heavy doses of fertilizer were applied. Soils of both older and newer ponds on both farms had large accumulations of major cations, a large portion of which were water-soluble salts. There was no evidence of development of adverse soil quality in older ponds.