Application of eco-physiological quotients (qCO2 and qD) on microbial biomasses from soils of different cropping histories
TL;DR: In this article, metabolic quotients for CO2 and microbial-C-loss were studied on soil microbial communities under long-term monoculture (M) or continuous crop rotations (CR).
Abstract: Metabolic quotients for CO2C (qCO2C) and microbial-C-loss (qD) were studied on soil microbial communities under long-term monoculture (M) or continuous crop rotations (CR). Under defined laboratory conditions the mean qCO2C (unit CO2C unit−1 Cmic h−1) of different microbial biomasses from 17 M systems amounted to 1.097 μg CO2qCO2CC as compared to 0.645 μg CO2C of microbial biomasses from 19 CR systems. The 1.7 times higher CO2C release per unit biomass and time of microbial biomasses from M systems was significantly different at the P =0.001 level.
In addition, microbial C-loss in samples from M or CR plots was followed for 5 weeks. Again, mean qD per unit microbial biomass and time was 1.6 times higher (P = 0.01) for microbial biomasses from M systems (0.301 μg C, 14 soils) when compared with CR systems (0.188μg C, 14 soils).
These differences were not related to soil texture, Corg or pH of these soils. The effects of environmental influences (soil management) on the microbial pool in terms of a changing energy demand are discussed.
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TL;DR: In this paper, the metal immobilization and phytoavailability of Cd, Cu and Pb was examined using naturally contaminated shooting range and spiked soils using chicken manure and green waste-derived biochar.
Abstract: Biochar has attracted research interest due to its ability to increase the soil carbon pool and improve crop productivity. The objective of this study was to evaluate the metal immobilizing impact of chicken manure- and green waste-derived biochars, and their effectiveness in promoting plant growth. The immobilization and phytoavailability of Cd, Cu and Pb was examined using naturally contaminated shooting range and spiked soils. Biochar samples prepared from chicken manure and green waste were used as soil amendments. Application of biochar significantly reduced NH4NO3 extractable Cd, Cu and Pb concentrations of soils, indicating the immobilization of these metals. Chicken manure-derived biochar increased plant dry biomass by 353 and 572% for shoot and root, respectively with 1% of biochar addition. This might be attributed to reduced toxicity of metals and increased availability of nutrients such as P and K. Both biochars significantly reduced Cd, Cu and Pb accumulation by Indian mustard (Brassica juncea), and the reduction increased with increasing amount of biochar application except Cu concentration. Metal sequential fractionation data indicated that biochar treatments substantially modified the partitioning of Cd, Cu and Pb from the easily exchangeable phase to less bioavailable organic bound fraction. The results clearly showed that biochar application was effective in metal immobilization, thereby reducing the bioavailability and phytotoxicity of heavy metals.
915 citations
Cites background or methods from "Application of eco-physiological qu..."
...The bottles were incubated for 24 h at 22°C (Anderson and Domsch 1990)....
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...Soil basal respiration and dehydrogenase activity (DHA) were analyzed using moist samples to monitor microbial activity (Anderson and Domsch 1990; Casida et al. 1964; Singh and Singh 2005)....
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TL;DR: The sensitivity of soil organic carbon (Corg) and microbial carbon measurements, and the Cm~,/Co, ratio, to reflect climatic, vegetation, cropping and management history was investigated using a range of topsoils in New Zealand.
Abstract: The sensitivity of soil organic carbon (Corg) and microbial carbon (Cmic) measurements, and the Cm~,/Co,, ratio, to reflect climatic, vegetation, cropping and management history was investigated using a range of topsoils in New Zealand. The Cmic generally comprised 1-4% of Corg, with the proportion being consistently greater under pastures, than the equivalent soil under native forest, exotic forest or arable cropping. However, absolute values differed markedly between soils and were greatly influenced by texture, mineralogy and the Corg content. The Cmic recovered more rapidly than Corg on returning to pasture following cropping. There was a generally greater Corg content in those soils from the areas with higher precipitation, but the precipitation-evaporation quotient proposed by Insam et al. (Soil Biol. Biochem. 1989, 21, 211-21) to predict the relationship between Cmic and Corg, greatly underestimated the Cmic content of New Zealand soils and there was too great a scatter in the data to derive a revised regression formula. The Cmic and the Cmic/Cor, ratio are useful measures to monitor soil organic matter and both provide a more sensitive index than COrg measured alone. However, under typical climatic and land use conditions in New Zealand, the values do not appear readily transferrable between soils. To ascertain whether a soil has achieved equilibrium in organic matter status, it will be necessary to establish reference values to which a tested soil can be compared.
816 citations
TL;DR: In this article, the effects of irrigation-induced salinity and sodicity on the size and activity of the soil microbial biomass in vertic soils on a Zimbabwean sugar estate were investigated.
Abstract: The effects of irrigation-induced salinity and sodicity on the size and activity of the soil microbial biomass in vertic soils on a Zimbabwean sugar estate were investigated. Furrow-irrigated fields were selected which had a gradient of salinity and sugarcane yield ranging from good cane growth at the upper ends to dead and dying cane at the lower ends. Soils were sampled under dead and dying cane, poor, satisfactory and good cane growth and from adjacent undisturbed sites under native vegetation. Electrical conductivity (EC) and sodium adsorption ratio (SAR) of saturation paste extracts was measured, as well as the exchangeable sodium percentage (ESP). There was a significant negative exponential relationship between EC and microbial biomass C, the percentage of organic C present as microbial biomass C, indices of microbial activity (arginine ammonification and fluorescein diacetate hydrolysis rates) and the activities of the exocellular enzymes beta-glucosidase, alkaline phosphatase and arylsulphatase but the negative relationships with SAR and ESP were best described by linear functions. By contrast, the metabolic quotient increased with increasing salinity and sodicity, exponentially with EC and linearly with SAR and ESP. Potentially mineralizable N, measured by aerobic incubation, was also negatively correlated with EC, SAR and ESP. These results indicate that increasing salinity and sodicity resulted in a progressively smaller, more stressed microbial community which was less metabolically efficient. The exponential relationships with EC demonstrate the highly detrimental effect that small increases in salinity had on the microbial community. It is concluded that agriculture-induced salinity and sodicity not only influences the chemical and physical characteristics of soils but also greatly affects soil microbial and biochemical properties. (C) 2003 Elsevier Science Ltd. All rights reserved.
796 citations
TL;DR: In this paper, soil samples were collected from adjacent well-stocked Shorea robustanatural forest, land reforested with Acacia, grassland and cultivated land, and soil degradation index showed that soil quality deteriorated significantly (44%) under cultivation, while in sites revegetated with fast growing Acacia or grasses, it improved by 6−16%.
733 citations
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TL;DR: The principles of ecological succession bear importantly on the relationships between man and nature and needs to be examined as a basis for resolving man’s present environmental crisis.
Abstract: The principles of ecological succession bear importantly on the relationships between man and nature. The framework of successional theory needs to be examined as a basis for resolving man’s present environmental crisis. Most ideas pertaining to the development of ecological systems are based on descriptive data obtained by observing changes in biotic communities over long periods, or on highly theoretical assumptions; very few of the generally accepted hypotheses have been tested experimentally. Some of the confusion, vagueness, and lack of experimental work in this area stems from the tendency of ecologists to regard “succession” as a single straightforward idea; in actual fact, it entails an interacting complex of processes, some of which counteract one another.
4,419 citations
TL;DR: The respiratory method provides reproducible estimates of biomass size within 1–3 h after soil amendment, and can be combined without difficulty with a selective inhibition method for determination of bacterial and fungal contributions to soil metabolism.
Abstract: A method is described for the rapid and objective estimation of the amount of carbon in the living, non-resting microbial biomass of soils. The method, which is based on the initial respiratory response of microbial populations to amendment with an excess of a carbon and energy source, was quantified using an expanded version of Jenkinson's technique.
The simultaneous application of the two methods to 50 soil samples showed a highly significant correlation (r = 0.96) between both. From this correlation it could be deduced that at 22°C, a substrate-induced maximal respiratory rate of 1 ml CO2· h−1 corresponds to c. 40 mg microbial biomass C. Evidence supporting these results was obtained from pure culture studies. The various soil types investigated were collected from agricultural as well as forest sites and they contained between 15 and 240 mg microbial C·100g dry soil−1. The respiratory method provides reproducible estimates of biomass size within 1–3 h after soil amendment. It can be combined without difficulty with a selective inhibition method for determination of bacterial and fungal contributions to soil metabolism.
2,787 citations
TL;DR: A comparative regression analysis of permanent monoculture plots with continuous crop rotation plots showed both to be highly significantly different at the P = 0.001 level: the regression line of continuous crop rotations shows a steeper slope, suggesting that a higher concentration of microbial carbon is characteristic of the crop rotation.
Abstract: The ratio of microbial biomass carbon (C mic ) to total organic carbon (C org ) was measured in soils from long-term agricultural experiments located in the temperate climatic zone of Central Europe. One hundred and thirty-four plots located in 26 experimental sites were analysed. This survey of C mic -to-C org ratios indicated no universal equilibrium constant. In contrast, a comparative regression analysis of permanent monoculture plots (M) with continuous crop rotation plots (R) showed both to be highly significantly different at the P = 0.001 level: the regression line of continuous crop rotations shows a steeper slope, suggesting that a higher concentration of microbial carbon is characteristic of the crop rotation. The regressions accounted for 87% (M) and 94% (R) of the variances in the data, respectively. Mean % C mic in C org amounted to 2.3 for permanent monocultures and to 2.9 for continuous crop rotations, respectively, of the simplest, the mineral fertilizer management. The differences in C-to-C ratios between the two management systems is thought to be caused by the difference in cropping management rather than by soil texture, i.e. clay content. These C mic -to-C org ratios rose to 4 or 3.7% in both plots under monoculture and plots under rotation, when the plots had received organic fertilizer the year prior to sampling. This rise in C mic over C org is seen as a transient rather than an absolute phenomenon and is believed to be due to the easily available carbon fraction of the introduced organic materia. Linearity of the C mic -to-C org relationship seems to be expressed only up to 2.5% C org . Regressions of C mic -to-N t were as well highly significant ( P =0.001) and in addition, the comparative regression analysis between M and R plots.
1,226 citations