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Paul (Eldor A.) Collection

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https://hdl.handle.net/10217/100513
This digital collection includes articles by Eldor A. Paul, a Senior Research Scientist at the Natural Resource Ecology Laboratory and a Professor in the Department of Soil and Crop Sciences at Colorado State University, Fort Collins. Eldor has had a lifelong interest in teaching and research in both grassland ecology and agroecosystems, ranging from wheat fields in Canada, through corn-belt rotations in the Great Lakes region of the US, into the afforested systems in California and Colorado.

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Browsing Paul (Eldor A.) Collection by Author "Anderson, D. W., author"

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    A comparison of humic fractions of Chernozemic and Luvisolic soils by elemental analyses, UV and ESR spectroscopy
    (Colorado State University. Libraries, 1974-11) Paul, E. A., author; Anderson, D. W., author; Russell, D. B., author; St. Arnaud, R. J., author; Agricultural Institute of Canada, publisher
    The Ah horizons of a Brown–Dark Brown–Black–Dark Gray–Gray Luvisolic sequence of Canadian grassland and forest soils were studied. Clay-associated humus was present in greater proportions in the grassland than in forest soils, particularly in the grassland soils of the more arid regions. Amounts of alkali-pyrophosphate-extractable humus increased in the Brown to Gray Luvisolic sequence. Alkali-pyrophosphate-extractable humic acid (HA-A) contents were greatest in the Black and Dark Gray soils. C:H ratios, extinction coefficients at 280 nm (E280), and resistance to acid hydrolysis of the HA-A and clay-associated HA-B increased in the Brown to Gray Luvisolic sequence. Free radical concentrations were least for the Brown and Dark Brown soils, moderate for the Black and greatest for the Gray Luvisolic soils. The data suggest an increase in the proportion of aromatic components in the humic acids in going from the Brown to the Gray Luvisolic soils. An objective, multivariate similarity analysis based on 22 humus characteristics showed a relationship between soil zone or soil environment and the nature of the soil's humus.
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    Decomposition of wheat straw and stabilization of microbial products
    (Colorado State University. Libraries, 1989-02) Voroney, R. P., author; Anderson, D. W., author; Paul, E. A., author; Agricultural Institute of Canada, publisher
    This research examined the effects of soil environment on the decomposition of cereal crop residues and stabilization of microbial products in the field. Microplots at semi-arid and subhumid field sites were amended with 14C-, 15N-labelled wheat straw and with 14C-labelled glucose plus 15N-labelled NH4NO3 and the fate of the residual C and N was monitored over 10 yr. Mineralization of C and N derived from wheat straw was greater at the site in the more moist environment in the short term (2 yr). In the long term (up to 10 yr), however, the residual C and N at this site decayed at a slightly slower rate, providing evidence of stabilization of organic material in chemically resistant forms, as compared to possible physical protection in the semi-arid clay-textured soil. The total recovery of labelled N was 22.5–24% in the harvested crops with 13.4–16% remaining in the surface soil by the end of the study. Mineralized labelled organic N was used with an efficiency ranging from 32 to 51%. However, after summer fallow the crop apparently used mineralized labelled N with an efficiency of only 7%. This study showed that moistness of the soil environment has a considerable effect on residue decomposition. Stabilization of humic material derived from residues relates more to the recalcitrance of microbial products and their interactions with soil mineral colloids than to the nature of the original residue.
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    Extraction and charaterization of humus with reference to clay-associated humus
    (Colorado State University. Libraries, 1974-08) Anderson, D. W., author; Paul, E. A., author; St. Arnaud, R. J., author; Agricultural Institute of Canada, publisher
    An extraction-fractionation method was developed with which it is possible to isolate 60–67% of the humus of Chernozemic and Luvisolic soils. Two humic acid fractions were obtained: (1) a conventional alkali-pyrophosphate extractable HA-A; (2) a clay-associated HA-B fraction isolated after ultrasonic dispersion, in water, of the residue of the alkali-pyrophosphate extraction. As compared to the HA-A, the HA-B fractions had lower C contents but greater N contents, narrower C:H ratios, higher molecular weights, and less resistance to hydrolysis in 6 N HCl. It was concluded that the HA-B is a weakly humified, potentially labile humic constituent stabilized by adsorption to clay. Spectral measurements on low-ash (< 2 %) humic acids showed a positive correlation between extinction coefficient at 280 nm (E280) and C:H ratio, and negative correlations between E280 and percent of hydrolyzable C and N. The E4:E6 ratio was related to molecular weight, as determined by agar gel filtration, increasing with decrease in molecular weight.
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    Organo-mineral complexes and their study by radiocarbon dating
    (Colorado State University. Libraries, 1984-03) Paul, Eldor A., author; Anderson, D. W., author; Soil Science Society of America, publisher
    The objective of this study was to investigate the long-term cycling of organic C in cultivated soils by radiocarbon dating. Samples from a clayey Haploboroll soil (Indian Head) taken in 1963 and 1978 showed a general reduction in radiocarbon age of the whole soil of 20%. This was attributed to the enrichment of 14C in the atmosphere because of nuclear explosions in the 1960s, and its subsequent incorporation into organic matter. Relative decreases in age were least for nonhydrolyzable C and the aromatic HA-A, the oldest and least active fractions. The apparent age of the humin and clay-associated HA-B decreased much more, indicating their greater involvement in short-term cycling. A second clayey Haploboroll soil (Melfort) was studied by chemical fractionation and separation into size fractions after ultrasonic dispersion. The HA-A and coarse clay-associated organic C were oldest, with a much younger date for fine-clay-associated organic C. Fulvic acids purified by dialysis to eliminate materials less than 2000 molecular weight had an old date of 1140 ± 35 yr. Size fractionation of two other Boroll soils indicated young radiocarbon ages (radiocarbon enrichment) of fine clay-associated organic C. These findings are discussed in terms of the cycling of organic matter and nutrients. Particular attention is given to clay-humus interactions and their importance in protecting otherwise labile humic materials to provide a substantial pool of moderately available nutrients.