University of Minnesota, Duluth
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Nitrate-nitrogen in effluent from agricultural tile drains in California
No full textSubsurface drainage water of agricultural lands collected in tile lines may contain nitrate-nitrogen which serves to pollute surface waters. The objective of the research was to determine quantities and concentrations of nitrate-nitrogen in tile drainage and their relationship to soil, fertilizer input, crop, and time with respect to water applicaiton. The first research phase consisted of extensive monitoring of tile drainage effluents collected in important agricultural areas in California. More intensive investigation of nitrate-nitrogen within a few soil profiles was done during the second phase. Nitrate-nitrogen concentrations were not well-correlated with any measured parameter. The amount of nitrate-nitrogen contained in tile effluent was quite well-correlated with total water discharge and fertilizer nitrogen application. Higher amounts of nitrate-nitrogen were removed from coarse-textured soil profiles as compared to profiles containing a layer of fine-textured material. Some alluvial soils on the west side of the San Joaquin Valley apparently contain significant native nitrogen which contributes both to high nitrate-nitrogen concentrations and total mass emissions in tile effluent. Implications of the research findings to nitrogen and water management to achieve a desired water quality standard are discussed. It appears that the most positive approach to controlling nitrate-nitrogen in irrigated agriculture is through control of leaching
Geologic nitrogen and the occurrence of high nitrate soils in the western San Joaquin Valley, California
No full textThe content of total, nitrate, fixed, exchangeable, and organic nitrogen in Cretaceous and Tertiary formations in two representative drainage basins of the east central Diablo Range was determined. The results of these analyses showed that high concentrations of organic nitrogen (up to 1,200 ?g/g) occur predominantly in the Cretaceous formations while high concentrations of nitrate (up to 4,800 ?g/g) occur predominantly in the younger Tertiary sediments. The concentrations of fixed and exchangeable ammonium were variable and generally low
Scaling of field-measured soil-water properties: I. Methodology
No full textConcepts of similar soil and scaling are applied to investigate the spatial variability of the field-measured soil-water properties, soil-water pressure head, hydraulic conductivity, and soil-water diffusivity associated with unsaturated flow. The classical, analytical aspects of scale factors as regards the invariance of the flow equations expressed in terms of “reduced variables” are reviewed and extended by considering stochastic aspects of random variations in soil-water properties. It is demonstrated that scaling can best be achieved when soil-water properties are represented by a set of related model functions
Scaling of field-measured soil-water properties: II. Hydraulic conductivity and flux
No full textConcepts of similar soil and scaling are applied to investigate the spatial variability of the field-measured soil-water properties, soil-water pressure head, hydraulic conductivity, and soil-water diffusivity associated with unsaturated flow. The classical, analytical aspects of scale factors as regards the invariance of the flow equations expressed in terms of “reduced variables” are reviewed and extended by considering stochastic aspects of random variations in soil-water properties. It is demonstrated that scaling can best be achieved when soil-water properties are represented by a set of related model functions
Factors affecting vegetation on a serpentine soil: II. Chemical composition of foliage and soil
No full textThe Use of Computer-Assisted Mapping Techniques to Delineate Potential Areas of Salinity Development in soils: I. A Conceptual Introduction
No full textSeveral interacting factors are generally associated with the development of soil salinity on irrigated lands of the arid Southwest. Notable examples include physical edaphology (clay content and soil permeability), depth to the perched water table, salinity of the perched groundwater, and irrigation efficiency. By creating map overlays of these properties and noting the areas of intersection of specific levels or thresholds of these properties, areas can be delineated that demonstrate varying propensities for salt accumulation in the soil profile
Experimental studies on poisoning pocket gophers
No full textField and laboratory tests on poisoning the Sacramento Valley pocket gopher (Thomomys bottae navus Merriam) are here reported. Nine poisons (including common and newly discovered rodenticides) and many kinds of bait materials were evaluated, graded dosages of the best poisons were bioassayed, and the effects of season of year, lures, and refrigeration on bait performance were tested
Prevention of copper and iron turbidities in wine
No full textA search was conducted for a satisfactory substitute for potassium ferrocyanide in removing copper from wine to prevent formation of copper casse, at present the most important problem in wine stabilization. The most promising among the relatively nontoxic organic compounds tested was rubeanic acid. Cysteine and related sulfhydryl compounds and ascorbic acid precipitate excess copper, but further tests under winery conditions are needed. Aside from potassium ferrocyanide itself, the only other material that gave satisfactory results was an adsorption complex of potassium ferrocyanide and Prussian blue. Properly prepared and used—possibly with the addition of denatured protein—this complex would avoid contamination of the wine with ferrocyanide. Neither it nor rubeanic acid was as effective as the soluble ferrocyanide in removing iron from wine; but iron casses if troublesome might be dealt with by other means
Field testing of grape maturity
No full textSince harvesting grapes at the proper stage of maturity is essential to quality—whether the grapes are intended for winery, table, or raisin use—an accurate means of estimating maturity in the field is necessary. Experiments were designed to measure the reliability of three field sampling methods—individual berry, cluster, and whole vine—in order to provide a more rational basis for grower practice. The varieties tested were Semillion and Carignane in regions II, IV, and V, Thompson Seedless in regions IV and V, and Flame Tokay in region IV. The degree Balling, Abbé refractometer reading, per cent reducing sugar, per cent total acidity, and pH were determined on all samples. According to these analyses, the three methods compare very favorably. It is suggested, however; that berry sampling, since it is the simplest and most rapid of the three methods, may be the most practical