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Soil Biology & Biochemistry | 1981

Microcalorimetry and other methods to assess biomass and activity in soil

G.P. Sparling

Abstract The heat output from 12 soils from the north east of Scotland was measured using microcalorimetry. The results were compared with the biomass estimated by the amount of carbon mineralized after chloroform fumigation and by the rate of respiration in substrate-amended soil and also with the basal rate of respiration, the ATP content and the activities of amylase and dehydrogenase. Microcalorimetric values correlated well with the rate of respiration and to a lesser extent with the biomass, ATP content and amylase activity. It is suggested that microcalorimetry is a useful additional technique for assessing the overall biological activity of a soil.


Soil Biology & Biochemistry | 1981

Microbial biomass and activity in soils amended with glucose

G.P. Sparling; B.G. Ord; D. Vaughan

Abstract Four contrasting soils were amended with glucose at concentrations up to 10 mg g−1 soil. The soils were incubated at 22°C for 14 days and the biomass determined at various times by chloroform fumigation or substrate-induced respiration. The adenosine triphosphate (ATP) content or the amylase and dehydrogenase activities were also determined. The size of the increases in biomass, ATP content and the enzyme activities was generally related to the amount of glucose added. The initially higher ATP levels quickly declined, and apparent substrate conversion figures up to 84% indicated that substrate-induced respiration overestimated the biomass. There were generally no significant correlations between ATP, biomass or enzyme activities.


Soil Biology & Biochemistry | 1981

Changes in microbial biomass and activity in soils amended with phenolic acids

G.P. Sparling; B.G. Ord; D. Vaughan

Abstract The phenolic acids p -hydroxybenzoic, ferulic, caffeic and vanillic acid, were added to soil of the Countesswells series that had been fallow or carried crops of potatoes, peas or barley for two consecutive years. Changes in phenolic acid concentration, the soil biomass, the respiration rate, and soil amylase activity were measured over 28 days. All the phenolic acids were sorbed by the soils which was generally in the order caffeic > ferulic = vanillic > hydroxybenzoic acid. The phenolic acids stimulated soil respiration and increased the biomass as determined by the substrate-induced respiration method. but the fumigation method of biomass assessment gave anomalous results. The soil amylase activity was initially increased by phenolic acid amendments but soon decreased, and after 7 days was less than in non-amended soil although activity had increased again after 28 days. The rates of respiration and the total phenolic acid concentrations were similar to unamended controls after 28 days. The immediate respiration response, measured 1–6 h after amendment, indicated that caffeic acid gave the largest initial response of the phenolic tested, this being 55–72% of that given by glucose. Soil from the potato plot showed the highest immediate response to the phenolic acid amendments measured as a proportion of the respiration response to glucose. The findings suggest that some crops stimulate the growth of phenolic-acid degrading organisms.


Soil Biology & Biochemistry | 1986

Microbial biomass in organic soils: estimation of biomass C, and effect of glucose or cellulose amendments on the amounts of N and P released by fumigation.

G.P. Sparling; B.L. Williams

Abstract The microbial biomass C in forest humus from beneath Scots pine (Pinus sylvestris L.), Japanese larch [Larix kaempferi (Lamb.) Carr.] and surface soil from Calluna heath, was estimated by both direct microscopy and by the substrate-induced-respiration (SIR) method of Anderson and Domsch. There was reasonable agreement between the methods with the larch and heath land samples, but with the pine, the SIR method gave much lower estimates of the biomass. Total biomass C was greatest in the larch samples and in all sites was dominated (>89%) by fungi. The effect of glucose, cellulose and NPK salts on the SIR biomass C and on the amounts of N and P released by CHCl3-fumigation of the pine and larch humus, and a mineral soil, were compared. In general, the effects of glucose and cellulose were similar—the biomass C was increased, but the “flushes” of soluble N and inorganic P decreased. The addition of NPK along with the C substrate did not increase the flushes of N and P. The SIR method appears a useful technique to estimate the biomass C on acid organic soils, but the flushes of N and P were not a reliable measure of the nutrient content of the biomass, especially on C-amended samples.


Soil Biology & Biochemistry | 1982

Critical evaluation of the acetylene reduction test for estimating the activity of nitrogen-fixing bacteria associated with the roots of wheat and barley

G. Lethbridge; M.S. Davidson; G.P. Sparling

Abstract The reliability of the C2H2 reduction test for estimating the activity of N2-fixing bacteria associated with the roots of cereals has been evaluated in Scottish soils. Six wheat cultivars, including two chromosome substitution lines, and five barley cultivars were grown in a glasshouse in nine soils from the North East of Scotland. All the soils exhibited C2H4 oxidase activity which was completely inhibited by 0.0001–0.1 atm C2H2. Over-estimation of C2H2 reduction, resulting from the accumulation of endogenous C2H4, could, therefore, occur in assays of undisturbed plants, with the real possibility of deducing the existence of N2-fixation where none existed. However, radiolabelled C2H2 reduction tests on undisturbed plants producing 2.4–18.0 μmol C2H4 day−1, showed that all the C2H4 had been derived from the C2H2. With less active plants, the source of the C2H4 could not be accurately determined by this tracer method. These low rates of C2H4 production ( The highest C2H2 reduction activities were observed in soils at maximum water holding capacity (MWHC). Roots removed from these soils reduced C2H2 immediately, if the initial partial pressure of O2 (pO2) was Even with the possibility of over-estimation of N2-fixation, the C2H2 reduction activities measured were considered to be too low to contribute significantly to the nitrogen requirement of the cereals grown under field conditions in Scotland. Some guidelines for screening programmes of N2-fixation associated with the roots of grasses are suggested.


Soil Biology & Biochemistry | 1981

Heat output of the soil biomass

G.P. Sparling

Abstract Amending soils with glucose (5 mg g −1 ) resulted in an immediate increase in microbial activity and within 30 min the rates of heat output and respiration at 22° C were increased by up to 17.8 and 23.4 times, respectively. The increased rate of heat output remained stable for up to 6 h and there was good correlation with the amount of CO 2 respired. The soil biomass was calculated by the method of Anderson and Domsch (1978). The rate of heat output of the biomass varied in different soils and ranged from 11.5 to 83.7 Jh −1 g −1 biomass C. In glucose-amended soils, however, the rate of heat output was much more consistent; the soils were in two groups having between 169–265 Jh −1 g −1 biomass C or 454–482 J h −1 g −1 biomass C, both the latter two soils were from pasture. The increased rate of heat output from the amended soils was lower than expected from the respiration rate and the heat of oxidation of glucose, suggesting that a proportion of the CO 2 respired was from catabolism of substrates other than glucose. Use of 14 C-glucose confirmed that between 57–91% of the CO 2 was derived from the glucose substrate.


Soil Biology & Biochemistry | 1979

Ammonium and nitrate in the rhizosphere of spring barley, hordeum vulgare L., and take-all disease

J.F. Darbyshire; M.S. Davidson; N.M. Scott; G.P. Sparling; P.J. Shipton

Abstract The incidence and severity of take-all disease, due to Gaeumannomyces graminis (Sacc.) Arx & Olivier var. tritici Walker, was observed on spring barley plants growing in soil in two glasshouse experiments. Soil amendments of NH+4-N significantly increased the number of diseased plants and roots during the first month after germination in comparison with controls unamended with N (P


Soil Biology & Biochemistry | 1983

Amelioration of the phytotoxicity of phenolic acids by some soil microbes

D. Vaughan; G.P. Sparling; B.G. Ord


Soil Biology & Biochemistry | 1982

Measurement of the microbial biomass in composted wheat straw, and the possible contribution of the biomass to the nutrition of Agaricus bisporus

G.P. Sparling; T.R. Fermor; D.A. Wood


Soil Biology & Biochemistry | 1983

A comparison of methods for measuring ATP and microbial biomass in soils

G.P. Sparling; F. eiland

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D.A. Wood

Crops Research Institute

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T.R. Fermor

Crops Research Institute

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