scholarly journals Measurement of microbial biomass N:C by chloroform fumigation-incubation

1997 ◽  
Vol 77 (4) ◽  
pp. 507-514 ◽  
Author(s):  
D. Harris ◽  
R. P. Voroney ◽  
E. A. Paul
Keyword(s):  
Microbial Biomass ◽  
Soil Microbial Biomass ◽  
C:N Ratio ◽  
Residual Fraction ◽  
Model Parameters ◽  
C Mineralization ◽  
Microbial Biomass Nitrogen ◽  
Soil Microbial ◽  
Biomass N ◽  
Chloroform Fumigation

We present a calculation for soil microbial biomass N:C ratio determined from a 10-d incubation following chloroform fumigation. The calculation is based on a mathematical model of the N content of the pre- and post-fumigation soil microbial biomass and the growth yield of the biomass that develops after fumigation. Biomass N is calculated from the N:C ratio and biomass C. The mineralization of bacteria and fungi, with different N contents, added to fumigated soils was used to establish the model parameters. The model was tested against an independent set of measurements and considers two assumptions: 1) The ratio of N:C mineralized from killed biomass is equal to the ratio of N:C mineralized from soil non-biomass constituents. 2) More realistically, the N and C mineralization in the fumigated soil, from sources other than killed biomass, is a residual fraction of the N and C mineralization in the unfumigated soil. Biomass C:N ratios calculated without a control correction (assumption 1) were, on average, 20% wider than corrected values (assumption 2). Biomass N calculated as the product of N:C and biomass C was compared with published values for several data sets. The new calculation method was robust even when net immobilization of N followed fumigation. Key words: Soil microbial biomass, nitrogen, chloroform fumigation, C:N ratio

scholarly journals Defining a realistic control for the chloroform fumigation-incubation method using microscopic counting and 14C-substrates

1996 ◽  
Vol 76 (4) ◽  
pp. 459-467 ◽  
Author(s):  
William R. Horwath ◽  
Eldor A. Paul ◽  
David Harris ◽  
Jeannette Norton ◽  
Leslie Jagger ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Soil Microbial Biomass ◽  
Microbial Biomass Carbon ◽  
Soil Depth ◽  
Temporal Trends ◽  
Biomass Carbon ◽  
Soil Microbial ◽  
Microbial C ◽  
Parameter Values ◽  
Chloroform Fumigation

Chloroform fumigation-incubation (CFI) has made possible the extensive characterization of soil microbial biomass carbon (C) (MBC). Defining the non-microbial C mineralized in soils following fumigation remains the major limitation of CFI. The mineralization of non-microbial C during CFI was examined by adding 14C-maize to soil before incubation. The decomposition of the 14C-maize during a 10-d incubation after fumigation was 22.5% that in non-fumigated control soils. Re-inoculation of the fumigated soil raised 14C-maize decomposition to 77% that of the unfumigated control. A method was developed which varies the proportion of mineralized C from the unfumigated soil (UFC) that is subtracted in calculating CFI biomasss C. The proportion subtracted (P) varies according to a linear function of the ratio of C mineralized in the fumigated (FC) and unfumigated samples (FC/UFC) with two parameters K1 and K2 (P = K1FC/UFC) + K2). These parameters were estimated by regression of CFI biomass C, calculated according to the equation MBC = (FC − PUFC)/0.41, against that derived by direct microscopy in a series of California soils. Parameter values which gave the best estimate of microscopic biomass from the fumigation data were K1 = 0.29 and K2 = 0.23 (R2 = 0.87). Substituting these parameter values, the equation can be simplified to MBC = 1.73FC − 0.56UFC. The equation was applied to other CFI data to determine its effect on the measurement of MBC. The use of this approach corrected data that were previously difficult to interpret and helped to reveal temporal trends and changes in MBC associated with soil depth. Key words: Chloroform fumigation-incubation, soil microbial biomass, microscopically estimated biomass, carbon, control, 14C

scholarly journals Impact of cadmium and lead on soil microbial biomass nitrogen of the botanical garden of ahmadu bello university, Zaria, Nigeria

2018 ◽  
Vol 3 (3) ◽  
pp. 94-97
Author(s):  
Oijagbe IJ ◽  
Abubakar BY ◽  
Edogbanya PRO
Keyword(s):  
Microbial Biomass ◽  
Room Temperature ◽  
Soil Microbial Biomass ◽  
Botanical Garden ◽  
Soil Samples ◽  
Microbial Biomass Nitrogen ◽  
Soil Microbial ◽  
Soil Microbial Biomass Nitrogen ◽  
Cadmium And Lead ◽  
Chloride Salts

This study is aimed at evaluating the effect of heavy metals on soil microbial processes. The effects of Lead (Pb) and Cadmium (Cd) at different concentrations were investigated over a period of eight weeks. Chloride salts of Pb and Cd were added singly and in combination to soil samples at room temperature (27°C) in different polythene bags. Samples were taken from the bags at two weeks interval and measurements were taken of the rate of microbial biomass nitrogen (MBN). The results showed that there was a significant decrease in the microbial biomass for all treated soils from the second week to the sixth week. But there was an observed increase in microbial biomass Nitrogen on the eight week. On the 6thweek, 40mgkg-1Cd gave the most significant decrease (16µg/g) and 1000mgkg-1 Pb gave the least significant decrease (70µg/g) of MBN.

scholarly journals Assessing the Response of Tomato Yield, Fruit Composition, Nitrogen Absorption, and Soil Nitrogen Fractions to Different Fertilization Management Strategies in the Greenhouse

HortScience ◽  
2019 ◽  
Vol 54 (3) ◽  
pp. 537-546
Author(s):  
Pengpeng Duan ◽  
Ying Sun ◽  
Yuling Zhang ◽  
Qingfeng Fan ◽  
Na Yu ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Soil Microbial Biomass ◽  
Organic N ◽  
Microbial Biomass N ◽  
Mineral N ◽  
Soil Microbial ◽  
Tomato Yield ◽  
Fruit Composition ◽  
Soil Microbial Biomass N ◽  
Biomass N

A greenhouse field experiment involving tomato (Solanum lycopersicum) was performed using different nitrogen (N) management regimes: sole application of differing rates of chemical N fertilizer (SC) (SC treatments: N0, N1, N2, and N3) and combined application of manure and chemical N fertilizer (MC) (MC treatments: MN0, MN1, MN2, and MN3). These were used to understand the relationship between comprehensive fruit composition, yield, and N fractions (soil mineral N; soil soluble organic N; soil microbial biomass N, and soil fixed ammonium) under greenhouse conditions. The results showed that the MC treatments significantly increased vitamin C and soluble sugar content compared with SC treatments. In addition, the MN2 treatment produced a high yield and had a positive effect on fruit composition. The N3 (563 kg N/ha) and MN3 (796 kg N/ha) treatments resulted in a high loss of N below the root zone (0–30 cm), consequently reducing N use efficiency. Soil mineral N, soil soluble organic N, and soil fixed ammonium tended to be higher during the first fruiting period, whereas soil microbial biomass N tended to be higher during the second fruiting period. MC treatments significantly increased the N fraction in the 0- to 30-cm soil layer; N fractions tended to be higher with the MN2 treatment. According to an optimum regression equation, soil fixed ammonium during the first fruiting period and soil microbial biomass N during the second fruiting period had a more significant influence on tomato yield and fruit composition. Overall, application MC at an appropriate rate (MN2: 608 kg N/ha) is a promising approach to achieving high yields and optimum taste, and it offers a more sustainable fertilizer management strategy compared with chemical N fertilization.

scholarly journals Pesticides effect on soil microbial ecology and enzyme activity- An overview

2016 ◽  
Vol 8 (2) ◽  
pp. 1126-1132 ◽  
Author(s):  
Sanjay Arora ◽  
Divya Sahni
Keyword(s):  
Microbial Biomass ◽  
Soil Microbial Biomass ◽  
Soil Microbes ◽  
Microbial Biomass Carbon ◽  
Soil Microbial Communities ◽  
Field Application ◽  
Microbial Biomass C ◽  
Microbial Biomass Nitrogen ◽  
Soil Microbial ◽  
Chemical Pesticides

In modern agriculture, chemical pesticides are frequently used in agricultural fields to increase crop production. Besides combating insect pests, these insecticides also affect the activity and population of beneficial soil microbial communities. Chemical pesticides upset the activities of soil microbes and thus may affect the nutritional quality of soils. This results in serious ecological consequences. Soil microbes had different response to different pesticides. Soil microbial biomass that plays an important role in the soil ecosystem where they have crucial role in nutrient cycling. It has been reported that field application of glyphosate increased microbial biomass carbon by 17% and microbial biomass nitrogen by 76% in nine soils at 14 days after treatment. The soil microbial biomass C increased significantly upto 30 days in chlorpyrifos as well as cartap hydrochloride treated soil, but thereafter decreased progressively with time. Soil nematodes, earthworms and protozoa are affected by field application rates of the fungicide fenpropimorph and other herbicides. Thus, there is need to assess the effect of indiscriminate use of pesticides on soil microorganisms, affecting microbial activity and soil fertility.

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