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Seasonal fluctuations in soil microbial biomass carbon, phosphorus, and activity in no-till and reduced-chemical-input maize agroecosystems (1992)

Buchanan, M. ; King, L. D.

Springer

Biology and fertility of soils 13 (1992), S. 211-217

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ISSN: 1432-0789

Keywords: Microbial biomass ; No-till agrosystem ; Maize ; Fumigation ; Extraction method

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Summary The soil microbial biomass contains important labile pools of C, N, P, and S, and fluctuations in its size and activity can significantly influence crop productivity. In cropping systems where fertilizer use is reduced or eliminated and green-manure legumes are used, nutrient availability is more directly linked to C-cycle dynamics. We observed the fluctuations in microbial biomass C and P, and in microbial biomass activity over three cropping seasons in continuous maize and 2-year maize-wheat-soybean rotation agroecosystems under no-till and reduced-chemical-input management. We estimated the concentrations of microbial C and P using fumigation-incubation and fumigation-extraction techniques for the surface 20 cm of Cecil and Appling series soils (clayey, kaolinitic, thermic, Typic Kanhapludults). There were significant seasonal fluctuations in microbial C and P under all cropping systems. Generally, the magnitude of fluxes and the quantity of microbial C and P tended to be higher in reduced-chemical-input systems due to tillage and incorporation of crop, weed, and legume residues. Over 3 years, the means for microbial C were 435 under reduced-input maize; 289 under no-till maize; 374 und the reduced-input crop rotation; and 288 mg kg-1 soil under the no-till rotation. The means for microbial P were 5.2 under reduced-input maize; 3.5 under no-till maize; 5.0 under the reduced-input rotation; and 3.5 mg kg-1 soil under the no-till rotation. Estimates of microbial activity, derived from CO2−C evolution and specific respiratory activity (mg CO2−C per mg biomass C), suggest that reduced-chemical-input management may cause a larger fraction of the biomass to be relatively “inactive” but may also increase the activity of the remaining fraction over that in no-till. Thus in these specific systems, the turnover of C and P through the microbial biomass with a reduced chemical input to the soil may be higher than under a no-till system.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00340578

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2

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Allelopathic activity in wheat-conventional and wheat-no-till soils: Development of soil extract bioassays (1992)

Blum, Udo ; Gerig, T. M. ; Worsham, A. D. ; [et al.]

Springer

Journal of chemical ecology 18 (1992), S. 2191-2221

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ISSN: 1573-1561

Keywords: Cover crops ; wheat ; Triticum aestivum ; soybean ; Glycine max ; soil extracts ; germination bioassays ; phenolic acids ; hydroxamic acids ; allelopathy ; slope analysis ; ivy-leaved morning glory ; Ipomoea hederacea ; crimson clover ; Trifolium incarnalum

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Abstract The primary objective of this research was to determine if soil extracts could be used directly in bioassays for the detection of allelopathic activity. Here we describe: (1) a way to estimate levels of allelopathic compounds in soil; (2) how pH, solute potential, and/or ion content of extracts may modify the action of allelopathic compounds on germination and radicle and hypocotyl length of crimson clover (Trifolium incarnatum L.) and ivyleaved morning glory (Ipomoea hederacea L. Jacquin.); and (3) how biological activity of soil extracts may be determined. A water-autoclave extraction procedure was chosen over the immediate-water and 5-hr EDTA extraction procedures, because the autoclave procedure was effective in extracting solution and reversibly bound ferulic acid as well as phenolic acids from wheat debris. The resulting soil extracts were used directly in germination bioassays. A mixture of phenolic acids similar to that obtained from wheat-no-till soils did not affect germination of clover or morning glory and radicle and hypocotyl length of morning glory. The mixture did, however, reduce radicle and hypocotyl length of clover. Individual phenolic acids also did not inhibit germination, but did reduce radicle and hypocotyl length of both species. 6-MBOA (6-methoxy-2,3-benzoxazolinone), a conversion product of 2-o-glucosyl-7-methoxy-1,4-benzoxazin-3-one, a hydroxamic acid in living wheat plants, inhibited germination and radicle and hypocotyl length of clover and morning glory. 6-MBOA, however, was not detected in wheat debris, stubble, or soil extracts. Total phenolic acids (FC) in extracts were determined with Folin and Ciocalteu's phenol reagent. Levels of FC in wheat-conventionaltill soil extracts were not related to germination or radicle and hypocotyl length of either species. Levels of FC in wheat-no-till soil extracts were also not related to germination of clover or morning glory, but were inversely related to radicle and hypocotyl length of clover and morning glory. FC values, solute potential, and acidity of wheat-no-till soil extracts appeared to be independent (additive) in action on clover radicle and hypocotyl length. Radicle and hypocotyl length of clover was inversely related to increasing FC and solute potential and directly related to decreasing acidity. Biological activity of extracts was determined best from slopes of radicle and hypocotyl length obtained from bioassays of extract dilutions. Thus, data derived from the water-autoclave extraction procedure, FC analysis, and slope analysis for extract activity in conjunction with data on extract pH and solute potential can be used to estimate allelopathic activity of wheat-no-till soils

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00984946

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3

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Use of water and EDTA extractions to estimate available (free and reversibly bound) phenolic acids in Cecil soils (1994)

Blum, U. ; Worsham, A. D. ; King, L. D. ; [et al.]

Springer

Journal of chemical ecology 20 (1994), S. 341-359

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ISSN: 1573-1561

Keywords: EDTA extraction ; water extraction ; NaOH extractions ; Cecil soil ; ferulic acid ; p-coumaric acid ; p-hydroxybenzoic acid ; vanillic acid ; sorption ; free phenolic acids ; reversibly bound phenolic acids ; allelopathy ; soil microbial ecology

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Abstract Sterile and microbe reinfested Cecil Ap and Bt soil materials amended with 0 to 5 µmol/g of ferulic acid,p-coumaric acid,p-hydroxybenzoic acid, or vanillic acid were extracted after varying time intervals with water, EDTA, or NaOH to characterize sorption of cinnamic and benzoic acid derivatives and to determine the effectiveness of water and EDTA extractions in estimating concentrations of free and reversibly bound phenolic acids in soils. Basic EDTA (0.5 M, pH 8) extractions and water extractions provided good estimates of both free and reversibly bound cinnamic acid derivatives, but not of benzoic acid derivatives. Neutral EDTA (0.25 M, pH 7) and water extractions, however, were effective for both cinnamic and benzoic acid derivatives Rapid initial sorption of both cinnamic and benzoic acid derivatives was followed by slow long-term sorption of the cinnamic acid derivatives. Slow long-term sorption was not observed for the benzoic acid derivatives. The amount of sorption of phenolic acids in soil materials was directly related to the concentration of phenolic acids added to soil materials. The addition of a second phenolic acid to the soil materials did not substantially affect the sorption of each individual phenolic acid. Sodium hydroxide extractions, which were made only after phenolic acids in phenolic acid-amended and non-amended soil material were depleted by microbes, confirmed that neutral EDTA and water extractions of soils can be used to make accurate estimates of baseline (residual) levels of free and reversibly bound phenolic acids available to soil microbes and, thus, potentially to seeds and roots.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02064442

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4

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Phenolic acid content of soils from wheat-no till, wheat-conventional till, and fallow-conventional till soybean cropping systems (1991)

Blum, U. ; Wentworth, T. R. ; Klein, K. ; [et al.]

Springer

Journal of chemical ecology 17 (1991), S. 1045-1068

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ISSN: 1573-1561

Keywords: Wheat ; Triticum aestivum ; soybean ; Glycine max ; no till ; conventional till ; soil extracts ; allelopathy ; phenolic acids ; Folin & Ciocalteu's phenol reagent ; HPLC

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Abstract Soil core (0–2.5 and/or 0–10 cm) samples were taken from wheat no till, wheat-conventional till, and fallow-conventional till soybean cropping systems from July to October of 1989 and extracted with water in an autoclave. The soil extracts were analyzed for seven common phenolic acids (p-coumaric, vanillic,p-hydroxybenzoic, syringic, caffeic, ferulic, and sinapic; in order of importance) by high-performance liquid chromatography. The highest concentration observed was 4 μg/g soil forp-coumaric acid. Folin & Ciocalteu's phenol reagent was used to determine total phenolic acid content. Total phenolic acid content of 0- to 2.5-cm core samples was approximately 34% higher than that of the 0- to 10-cm core samples. Phenolic acid content of 0- to 2.5-cm core samples from wheat-no till systems was significantly higher than those from all other cropping systems. Individual phenolic acids and total phenolic acid content of soils were highly correlated. The last two observations were confirmed by principal component analysis. The concentrations were confirmed by principal component analysis, tions of individual phenolic acids extracted from soil samples were related to soil pH, water content of soil samples, total soil carbon, and total soil nitrogen. Indirect evidence suggested that phenolic acids recovered by the water-autoclave procedure used came primarily from bound forms in the soil samples.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01402933

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5

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Modification of allelopathic effects ofp-coumaric acid on morning-glory seedling biomass by glucose, methionine, and nitrate (1993)

Blum, Udo ; Gerig, T. M. ; Worsham, A. D. ; [et al.]

Springer

Journal of chemical ecology 19 (1993), S. 2791-2811

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ISSN: 1573-1561

Keywords: Morning-glory ; Ipomoea hederacea ; growth inhibition ; p-coumaric acid ; allelopathic interactions ; leucine ; methionine ; glucose ; nitrate

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Abstract Studies of allelopathy have emphasized primarily the identification and quantification of phytotoxins in soils, with only limited attention directed toward how organic (carbon) and inorganic constituents (nutrients) in the soil may modify the action of such phytotoxins. In the present study, increasing carbon (C) levels (up to 108μg C/g soil) supplied as glucose, phenylalanine, orp-hydroxybenzoic acid did not alter morning-glory biomass, but similar C levels supplied as leucine, methionine, orp-coumaric acid were inversely related to morning-glory biomass. Similar joint action and multiplicative analyses were used to describe morning-glory biomass response to various C sources and to generate dose isolines for combinations ofp-coumaric acid and methionine at two NO3-N levels and for combinations ofp-coumaric acid and glucose at one NO3-N level. Methionine, glucose, and NO3-N treatments influenced the inhibitory action ofp-coumaric acid on biomass production of morning-glory seedlings. For example, results from the multiplicative analysis indicated that a 10% inhibition of morning-glory biomass required 7.5μgp-coumaric acid/g soil, while the presence of 3.68μg methionine/g soil thep-coumaric acid concentration required for 10% inhibition was only 3.75μg/ g soil. Similar response trends were obtained forp-coumaric acid and glucose. The higher NO3-N (14 vs. 3.5μg/g) treatments lowered the methionine and increased thep-coumaric acid concentrations required for 10% inhibition of morning-glory biomass. These results suggested that allelopathic interactions in soil environments can be a function of interacting neutral substances (e.g., glucose), promoters (e.g., NO3-N), and/or inhibitors (e.g., methionine andp-coumaric acid) of plant growth.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00980584

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