Response of microbial biomass to air-drying and rewetting in soils and compost

European Journal of Soil Biology, 2007

Soil biochemical properties are useful indicators of soil quality as they are very sensitive to disturbance. Sample storage or pretreatments could affect the results in these assays, which are normally determined on fresh samples, kept cold or frozen. The objectives of this study were to (i) evaluate the effect of air-drying or incubation of rewetted air-dried soil samples on microbial biomass carbon (MBC), basal soil respiration (BSR), qCO 2 and water soluble carbon (WSC), in soils from different locations, with different degradation status and sampling seasons, and (ii) assess if air-drying or incubation of rewetted air-dried soil samples is an accurate sample storage and pre-treatment procedure for these soil properties in soil quality evaluations under semiarid Mediterranean conditions. Our results showed that air-drying does not have the same effects on MBC, BSR, qCO 2 and WSC depending on the geographical situation and sampling date. It seems that the warmest and driest place and season show less variation when using air-dried soil samples, with values representative of those obtained under field-moist conditions. Short incubations (4, 8 and 12 days at 23 C) provoked a general decrease in all properties, probably due to labile organic compounds depletion. Hence, air-dried soils can be used as part of soil quality analysis to estimate these biochemical properties in summer time in the semiarid region of South-East Spain, because they have not suffered severe affections. Moreover, MBC could also be determined using air-dried soil in the driest zones during all year. In contrast, estimations with incubated soil samples are not, in any case, representative of field-moist soil values.

2008

In this study, the effect of the addition of various percentages of kitchen waste compost to soil on the soil microorganisms was investigated under laboratory conditions. The compost treatments were done by adding 10 % (compost treatment of 10% = CT-10), 20 % (CT-20) and 30 % (CT-30) compost to the soil. Compost and soil were mixed completely to get homogeneous mixtures. An untreated soil (CS) and a compost without soil (CC) were used as controls. The mixtures incubated for 28 days at 27 o C. The numbers of total bacteria for CT-20 and CT-30 increased by addition of kitchen waste compost, but compost was not effective for CT-10 at the end of the incubation. The actinomycetes numbers increased for CT-10 and CT-20, but decreased for CT-30 at final. In general, numbers of fungi-yeast in soils treated with compost, declined over the incubation period in the present study. Anaerobic bacteria number increased for CT-10 and CT-20 while decreased for CT-30. At the end of the incubation period, proteolytic bacteria numbers decreased for all treatments and controls.

Biology and Fertility of Soils, 2006

Olive-tree leaves (OL) were mixed with olive press cake (OPC) and extracted olive press cake (EPC) at 1:1 dw/dw ratios to prepare two composting mixtures (OL+ OPC and OL+EPC). Both CO 2 -C evolution and fluorescein diacetate (FDA) hydrolysis, determined as estimates of the microbial activity during composting, were related to temperature fluctuations in the compost piles, showing greater values at the temperature peaks, compared to the end, of each thermophilic phase. This, however, was only shown after handling and incubating samples at the temperatures of the compost mixtures at the sampling times and not at a low standard temperature. Incubating samples from thermophilic phases at low standard temperatures resulted in underestimation of the microbial activity occurring during composting. The effect of incubation temperature was less dramatic for FDA hydrolysis compared to CO 2 -C evolution measurements, probably reflecting the reduced dependence of enzymes involved in FDA hydrolysis on the respective temperatures. However, FDA hydrolysis was a less sensitive indicator of microbial activity, probably due to extracellular cleavage of fluorescein by persistent esterases, at lowered microbial activity phases. Total microbial biomass, estimated by the fumigation-extraction method, was not consistently related to temperature fluctuations during composting and showed a clear increase at the end of composting, probably resulting from a large slow-growing mycelial community colonising the end products. Since high temperatures did not induce sig-nificant non-microbial CO 2 -C release and FDA degradation, we propose the performance of microbial activity measurements during thermophilic composting phases at the actual temperatures evolving in the composts.

Biology and Fertility of Soils, 1993

Six composts from different sources (wheat and barley straw; coniferous bark; mixed hop rape and bark; two from household garbage; mixed paper dust and sewage sludge) were characterized by chemical methods, including various forms of N and organic matter fractionation, and by microbiological methods. The dehydrogenase activity, respiration rate, and arginine ammonification were investigated, which represent different aspects of C and N metabolism. Only a few significant correlations were found between different maturity indexes. Dehydrogenase activity was in agreement with the widely accepted humic acid C to fulvic acid C ratio and might therefore be acceptable as a maturity index. Arginine ammonification provided valuable information on the N status in composts; negative values indicated that considerable amounts of easily degradable organic compounds with wide C: N ratios were still present, which would lead to microbial immobilization of soil N after the application of these composts. A combination of dehydrogenase activity and arginine ammonification data led to an unambiguous classification of all composts, and is therefore recommended for further consideration; in contrast, chemical data were contradictory and markedly dependent on the original substrates. The respiration rate, which was closely correlated with the percentage of organic C, did not contribute to the assessment of compost maturity.

Biology and Fertility of Soils, 2018

We report a preliminary investigation into soil microbial biomass C, ATP, microbial community composition and gaseous emissions when an upland Chinese and an immediately adjacent paddy soil were incubated with increasing percentage water holding capacities (WHC) from 10% WHC to waterlogging for 10 days. The aim was to see what adaptations, if any, occur when a paddy soil is incubated under conditions of increasing soil moisture, from 10% WHC to waterlogging and an adjacent upland soil is subjected to the opposite moisture changes, from waterlogging to 10% WHC. The main differences were that soil ATP remained quite constant in the paddy soil, irrespective of the different WHCs while in the upland soil, it increased from a low level between 10 and 20% WHC to a maximum at 60% WHC declining to a similar low level as 10 and 20% when waterlogged. The most striking feature was that although there were significant changes in biomass C, ATP and biomass ATP concentrations, of up to 3-fold or more, due to changing soil moisture, the changes in relative abundance of the microbial community composition measured by gene sequencing, particularly for fungi, were small and often insignificant, especially between 40% WHC and waterlogging. There were significant changes in bacterial community composition between 10 and 40%, where 45 to 61% of bacteria responded to the change. However, the changes were very few between 40% WHC and waterlogging. Thus, there was no clear link between the large changes in microbial biomass and microbial community composition.

Plant litter decomposition is not a purely chemical or physical process, it is basically a biological one resulting from the diverse activities of microorganisms, protozoa and various other soil organisms like insects and worms. The bacteria and fungi play a very significant role in plant litter decomposition and humus formation. The fungi which colonized decaying substrates could use only simple substrates such as sugars and they referred as sugar fungi. Garrett suggested that the root infecting fungi open the way for a sequence of saprophytic sugar fungi, cellulose decomposers and finally lignin decomposers. The initial rates of losses of differrent components could be ranked as sugar > hemicelluloses> cellulose> lignin. During this succession, the substrates were found to become progressively depleted. This biochemically based succession was believed to be reflected in a taxonomic way as the Phycomycetes to be considered as sugar fungi, the Ascomycetes and Deuteromycetes as cellulolytic and finally Basidiomycetes as lignin decomposers.

Biology and Fertility of Soils, 2003

Composting of pruning waste, leaves and grass clippings was monitored by different parameters. A windrow composting pile, having the dimensions 2.5 m (height) x 30 m (length) was establish. The maturation of pruning waste compost was accompanied by a decline in NH4+-N concentration, water soluble C (WSC) and an increase in NO3–-N content. Both organic matter (OM) content and total N (TN) losses during composting followed a first-order kinetic equation. These results were in agreement with the microbiological activity measured either by the CO2 respiration or dehydrogenase (DH-ase) activity during the process. Statistically significant correlations were found between DH-ase activity, easily biodegradable organic C forms, NH4+-N and NO3–-N concentrations and organic matter content and N losses. For this reason, DH-ase activity and the CO2 evolution could be used as good indicators of pruning waste compost maturity. In contrast, humification parameters data from the organic matter fractionation did not agree with the initially expected values and did not contribute to the assessment of compost maturity. Neither the cation exchange capacity nor the germination index showed a clear tendency during the composting time, suggesting that these parameters are not suitable for evaluating the dynamics of the process.

1 The changes in population size of different microbial groups (total aerobic het-erotrophs, actinomycetes, fungi, fecal coliforms, ammonium-and nitrite-oxidizing bacteria, and denitrifying bacteria) and the activities of 19 different enzymes (three phosphatases, threeesterases, two proteases, three amino-peptidases, and eight gly-cosyl-hydrolases) were examined during cocomposting of poultry litter (a mixture of poultry manure, waste feed, feathers, and wood shavings) and yard trimmings (a mixture of grass clippings, leaves, and wood barks). Three piles with forced aeration were established by mixing 2:1 (vIv) ratio of poultry litter and yard trimmings. During composting, samples were taken at three different locations (top, middle, and bottom) of the forced aeration piles for microbial and enzyme analyses. Results demonstrated that population size of different microbial groups was not a limiting factor in this composting process as the microorganisms in the poultry litter + yard trimmings compost are in great abundance. Although the numbers of these microbial groups were reduced by high temperature, their populations multiplied rapidly as com-posting progressed. Fecal coliforms were eliminated by day 49, suggesting that the poultry litter + yard trimmings compost showed an overall increase in diversity and relative abundance of extracellular enzyines present as composting progressed. The population of fungi and actinomycetes (microorganisms active in degradation of cellulose , hemicellulose, and lignin) were positively correlated with esterase, valine amino-peptidase, a-galactosidase, l3-glucosidase, and lipase. Of all 19 enzymes examined , :B-galactosidase (enzyme involved in the hydrolysis of lactose) had the most significant positive correlation with microbial populations, such as total aerobic het-erotrophs, ammonicyn-and nitrite-oxidiiing bacteria, denitrifying bacteria, and fecal coliforms. Cystine amino peptidase, chymotrypsin, and trypsin showed no evidence of activity during the entire period of composting. This composting process repre-'seri.ted a combined activity of a wide succession of environments in the compost pile as one microbial group I enzyme overlapped the other and each emerged gradually as a result of the continual Ch3.J.lge in temperature as well as moisture content, °2 and CO2 level, and progressive breakdown of complex compounds to simpler ones.

Applied Soil Ecology, 2020

How litter at various stages of decomposition reacts to C and N additions is unclear. Here we used five substrates (litter, fermentation [Oe] layer, bulk soil, and the light fraction [LF] and heavy fraction [HF] of SOM) obtained from sites supporting five plant monocultures (Alnus glutinosa, Quercus robur, Salix caprea, Calamagrostis epigejos, or Picea omorica) with foliage C:N ratios ranging from 17 to 48. These plant-specific communities were experimentally planted on a post-mining heap and had affected the substrates used in this study for 40 years. Soils and other environmental factors were similar among the sites. Substrates were incubated for 3 weeks without nutrient addition or with C (glucose) or N (ammonium nitrate) addition, and microbial respiration was determined weekly. Substrate C:N ratios were determined at the start of the incubation and were highest for litter followed by Oe layer > LF > bulk soil and HF. Foliage C:N ratio was a better indicator of microbial respiration than the substrate C:N ratio, suggesting that the foliage C:N ratio reflected unmeasured leaf properties that determined microbial respiration. Respiration was highest in the litter followed by Oe layer > bulk soil > LF > HF. C addition increased respiration of the bulk soil (+39%), LF (+48%), and HF (+72%). Priming of SOM respiration was therefore higher in substrates with less available C. N significantly increased respiration of litter (+19%) but decreased respiration of bulk soil (−18%). The difference in respiration of HF vs. bulk soil following N addition suggested that, in addition to the stage of decomposition, environmental properties present in bulk soil but absent in HF may cause the reduction in respiration after N addition to bulk soil. Overall, the results indicate that differences in the contents of SOM fractions among soils will affect the responses of those soils to C and N additions.

Applied Biological Chemistry

Despite the widespread use of food waste compost as a soil organic amendment, there is limited information on how it affects the composition of the microbial community as well as its relationship on soil environmental factors. This study investigated the effects of food waste compost on soil microbial-community composition by using FAME analysis. It was established that the application of food waste composts in water saturated paddy and unsaturated upland soils increased pH levels, electrical conductivity (EC) values, total carbon (TC), and ESP contents. It also increased the total phospholipid fatty acid (T-PLFA) and fungi resulting in a significant rise in the fungi to bacterial ratio. Furthermore, microbial community composition shifted depending on the quantity of food waste compost applied after crop harvest in both paddy and upland soils. Also, a positive correlation was found between changes in soil microbial community and changes in TC, EC, and water availability for crop growth. These results suggest that soil fertility and its microbial composition depends on the amount of food waste compost applied in both water saturated the paddy and unsaturated upland soils. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.