Articles
MICROBIAL ACTIVITY OF TEN HORTICULTURAL PEATS UN-DER DIFFERENT INCUBATION CONDITIONS
Article number
891_2
Pages
33 – 39
Language
English
Abstract
The initial characteristics of potting-media have direct influence on plant growth.
When used as a potting-medium constituent, peat should thus be resistant to microbial degradation although such properties could be altered by fertilization and plant root exudates.
In this study, we investigate the effect of C and N additions on the microbial activity of 10 different peats under aerobic incubation condition.
These peats were obtained from Germany, Ireland, Latvia, Lithuania and Sweden.
Quadruplicate subsamples (each corresponding to 10 g oven dry weight) were taken from a given peat and subjected to: (1) no C and N inputs; (2) glucose, 1 g L-1; (3) cellulose, 1 g L-1; and (4) NH4NO3, 1 g N L-1. Each treatment was then placed in a 1.5-L glass jar, sealed tightly and incubated for 20 d at 25°C. Headspace gas was taken at the end of the incubation period and analysed for CO2 concentration using a gas chromatograph.
The von Post humification degree in the tested peats ranged from H3 to H7. The highest organic carbon (OC) and N, and the lowest organic matter (OM)
content was found in the strongly decomposed peats compared with the weakly
decomposed counterpart.
The mean basal respiration in the control treatments
varied between 136 and 341 µg CO2 g-1 d-1, with overall mean value of 237±72. The rate of evolved CO2 showed inverse relationships with the von Post humification degree (r=-0.50) and total organic C (r=-0.76) suggesting that the microbial activity in the strongly decomposed peats could be constrained by the presence of poor
quality organic carbon (i.e., such peats might be rich in recalcitrant C-sources that are not easily degraded by microorganisms). Both OM and C/N ratio had very poor correlations with microbial activity measured as evolved CO2, and hence cannot be used as predictors of microbial activity in Sphagnum-derived peats.
The rate of CO2 production in all peats was significantly increased after the addition of glucose in the range of 1.5- to 3.84-fold.
However, microbial activity in NH4NO3 treated peat samples was considerably lower than the respective control samples (38 to 55%). CO2 evolution in cellulose-amended samples was slightly higher than the control samples but considerably lower than glucose treated samples suggesting that the inclusion of cellulose-C containing potting mixes (e.g., wood bark, fibers and saw dust) into the tested horticultural peats may have little effect on their bio-stability.
In contrast, the addition of easily decomposable C sources (e.g., immature composts) could increase microbial activity in the final mix and thereby affect the bio-stability of peats during cropping regardless of their humification degree.
When used as a potting-medium constituent, peat should thus be resistant to microbial degradation although such properties could be altered by fertilization and plant root exudates.
In this study, we investigate the effect of C and N additions on the microbial activity of 10 different peats under aerobic incubation condition.
These peats were obtained from Germany, Ireland, Latvia, Lithuania and Sweden.
Quadruplicate subsamples (each corresponding to 10 g oven dry weight) were taken from a given peat and subjected to: (1) no C and N inputs; (2) glucose, 1 g L-1; (3) cellulose, 1 g L-1; and (4) NH4NO3, 1 g N L-1. Each treatment was then placed in a 1.5-L glass jar, sealed tightly and incubated for 20 d at 25°C. Headspace gas was taken at the end of the incubation period and analysed for CO2 concentration using a gas chromatograph.
The von Post humification degree in the tested peats ranged from H3 to H7. The highest organic carbon (OC) and N, and the lowest organic matter (OM)
content was found in the strongly decomposed peats compared with the weakly
decomposed counterpart.
The mean basal respiration in the control treatments
varied between 136 and 341 µg CO2 g-1 d-1, with overall mean value of 237±72. The rate of evolved CO2 showed inverse relationships with the von Post humification degree (r=-0.50) and total organic C (r=-0.76) suggesting that the microbial activity in the strongly decomposed peats could be constrained by the presence of poor
quality organic carbon (i.e., such peats might be rich in recalcitrant C-sources that are not easily degraded by microorganisms). Both OM and C/N ratio had very poor correlations with microbial activity measured as evolved CO2, and hence cannot be used as predictors of microbial activity in Sphagnum-derived peats.
The rate of CO2 production in all peats was significantly increased after the addition of glucose in the range of 1.5- to 3.84-fold.
However, microbial activity in NH4NO3 treated peat samples was considerably lower than the respective control samples (38 to 55%). CO2 evolution in cellulose-amended samples was slightly higher than the control samples but considerably lower than glucose treated samples suggesting that the inclusion of cellulose-C containing potting mixes (e.g., wood bark, fibers and saw dust) into the tested horticultural peats may have little effect on their bio-stability.
In contrast, the addition of easily decomposable C sources (e.g., immature composts) could increase microbial activity in the final mix and thereby affect the bio-stability of peats during cropping regardless of their humification degree.
Authors
Y. Amha, H. Bohne, G. Schmilewski, P. Picken, O. Reinikainen
Keywords
cellulose, CO2 evolution, glucose, NH4NO3, von Post humification degree
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