| 1. |
- Börjesson, Gunnar, et al.
(författare)
-
Markbiologisk uppföljning i åkermark : en undersökning av fosfolipidfettsyror (PLFA) som möjlig mikrobiologisk indikator
- 2010
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Monitoring and assessment of agricultural soils has become requested as means to detect changes in soil quality. Among possible microbial indicators for monitoring soil quality, the most common methods include microbial biomass, respiration, N mineralization and a community profiling method. Among the latter, the most used seem to be DGGE (denaturing gradient gel electrophoresis), PLFA (phospholipid fatty acids), and CLPP (community level physiology profile) analyses. Here we report results from an investigation of the PLFA analysis for the possible use as an indicator for monitoring soil quality. Soil samples were taken 2009 in the Ultuna soil organic matter field experi-ment, which was started in 1956 for investigating the long-term effect of mineral N fertilizers and different organic amendments on crop yields, soil organic matter changes and soil physical properties. PLFAs were extracted from top- and subsoils in ten treatments. PLFA concentrations were compared to other variables, such as total carbon, total nitrogen, pH and respiration, but also to other results reported earlier from the same experiment. Total PLFAs in topsoil samples (0-20 cm) were highest in the sewage sludge (O) treatment, which was almost reflected in subsoil samples, although the highest mean value among those samples was found for the farmyard manure (J) treatment. A good correlation was observed between total PLFAs in topsoil samples and total carbon, but total PLFAs were even better correlated with total nitrogen (r=0.81; p<0.0001). Subsoil samples (27-40 cm depth) reflected topsoil samples for total PLFAs, but the individual PLFAs revealed that the composition of the microbial communities were entirely different. The presence of cyclic fatty acids in the sewage sludge treatment indicated some kind of stress for gram-negative bacteria, probably caused by heavy metals, although a negative effect of the sewage sludge application could not be seen in other ways, e.g. crop yield. In conclusion, the PLFA analysis can give valuable information about the microbial community in soil samples. It can be used in a monitoring programme, although the recommendation is that it would be preferable to combine the PLFA analysis with other methods, for example CLPP, in order to determine trends and changes of microbial communities and activities in soils
|
|
| 2. |
- Börjesson, Gunnar, et al.
(författare)
-
Soil microbial community structure affected by 53 years of nitrogen fertilisation and different organic amendments
- 2012
-
Ingår i: Biology and Fertility of Soils. - : Springer Science and Business Media LLC. - 0178-2762 .- 1432-0789. ; 48, s. 245-257
-
Tidskriftsartikel (refereegranskat)abstract
- The Ultuna long-term soil organic matter experiment in Sweden (59'82A degrees N, 17'65A degrees E) was started in 1956 to study the effects of different N fertilisers and organic amendments on soil properties. In this study, samples were taken from 11 of the treatments, including unfertilised bare fallow and cropped fallow, straw with and without N addition, green manure, peat, farmyard manure, sawdust, sewage sludge, calcium nitrate and ammonium sulphate, with n = 4 for each treatment. Samples were taken from topsoil (0-20 cm) and subsoil (27-40 cm depth) and analysed for concentrations of phospholipid fatty acids (PLFAs), organic C, total N and pH. The results showed that the subsoil samples reflected the total PLFA content of the topsoil, but not the microbial community structure. Total PLFA content was well correlated with total organic C and total N in both topsoil and subsoil. Total PLFA content in topsoil samples was highest in the sewage sludge treatment (89 A +/- 22 nmol PLFA g dw(-1)). This contradicts earlier findings on microbial biomass in this sewage sludge-treated soil, which indicated inhibition of microorganisms, probably by heavy metals added with sludge. A switch towards microbial growth and faster decomposition of organic matter occurred around 2000, coinciding with lowered heavy metal content in the sludge. According to the PLFA data, the microbial community in the sewage sludge treatment is now dominated by Gram-positive bacteria. A lack of Gram-negative bacteria was also observed for the ammonium sulphate treatment, obviously caused by a drop in pH to 4.2.
|
|
| 3. |
- Ekblad, Alf, et al.
(författare)
-
Determination of Soil Respiration rates and d13C in situ using a spectroscopic Picarro G1101-i instrument
- 2010
-
Ingår i: Geophysical Research Abstracts. - 1607-7962. ; 12
-
Konferensbidrag (refereegranskat)abstract
- Variation in the d13C-signature of soil respiration can be used as a tracer in ecological research. Up until now, isotopic determinations have mainly been performed by gas sampling and expensive and complex laboratory IRMS analyses. Recently, user friendly, portable and less expensive spectroscopic instruments have become available on the market. However, if these instruments give reliable data in dynamic systems under highly variable temperatures and air humidity conditions is unknown. In this talk we will present results from the first summer of tests of the use of a Picarro G1101-i cavity ringdown spectroscopy instrument (size 43 x 25 x 59 cm; 26.3 kg) to determine the d13C of soil respiration in various systems.
|
|
| 4. |
- Kätterer, Thomas, et al.
(författare)
-
Roots contribute more to refractory soil organic matter than above-ground crop residues, as revealed by a long-term field experiment
- 2011
-
Ingår i: Agriculture, Ecosystems and Environment. - : Elsevier BV. - 0167-8809 .- 1873-2305. ; 141, s. 184-192
-
Tidskriftsartikel (refereegranskat)abstract
- We revisited the well documented and ongoing long-term 'Ultuna continuous soil organic matter field experiment' which started in 1956 at the Swedish University of Agricultural Sciences. The objective of the experiment is to quantify effects of six organic amendments and mineral N fertilizers on the crop and soil. We used the 'equivalent soil mass' concept for estimating changes in the topsoil carbon stocks in all 15 treatments. C inputs from amendments were measured and those from crops were calculated using allometric functions and crop yields. Clustering C inputs into seven categories by quality allowed us to calculate a 'humification' coefficient for each category. Here, these coefficients were simply based on the fraction of total C input that still remains in the topsoil after about 50 years. As indicated by previous studies, this coefficient was highest for peat, followed by sewage sludge, manure, sawdust and above-ground crop residues. The most interesting result from the current investigation is that the optimized coefficient for root-derived carbon was about 2.3 times higher than that for above-ground plant residues. The calculated results were found to be robust in a sensitivity analysis. Our findings strongly support the hypothesis that root-derived carbon contributes more to relatively stable soil C pools than the same amount of above-crop residue-derived (C) 2011 Elsevier B.V. All rights reserved.
|
|
| 5. |
- Menichetti, Lorenzo, et al.
(författare)
-
Chemical Properties and Biochemical Activity of Colonized and Abandoned Litter-Feeding Termite (Macrotermes spp.) Mounds in Chromic Cambisol Area on the Borana Plateau, Ethiopia
- 2014
-
Ingår i: Pedosphere. - 1002-0160 .- 2210-5107. ; 24, s. 399-407
-
Tidskriftsartikel (refereegranskat)abstract
- Termite (Macrotermes spp.) mounds are complex biological habitats originated by the termite activity and possessing peculiar physical, chemical and biochemical properties. In this study we examined the concentration of nutrients and the biochemical activity of abandoned soil and mounds colonized by termites of the genera Macrotermes located in the Borana District, Ethiopia. To elucidate the magnitude and persistence of the termite-induced effects, we also studied an abandoned mound, previously colonized by termites of the same genera formed on the same soil. Results confirmed that termite-colonized mounds are 'hot spots' of nutrient concentration and microbial activity in tropical soils. This is due to the termite driven litter input and decomposition. The abandoned mounds showed higher microbial biomass and activity and displayed a nutrient redistribution and a greater microbial activity than the adjacent soils. These findings allowed us to hypothesize a model of nutrient cycling in colonized soils and a partition of the relative roles of termites and soil microorganisms in nutrient location and turnover in tropical soils. These results may be also useful for the optimal management of termite-colonized soils.
|
|
| 6. |
- Menichetti, Lorenzo
(författare)
-
Improving our understanding of carbon cycling in agroecosystems by studying δ¹³C signatures in soil carbon stocks and fluxes : results from a Swedish long-term field experiment
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Soil carbon (C) storage has gained much attention in the past decade due to its potentially huge impact on climate change mechanisms. Particular focus has been paid to possible feedback mechanisms, whether soil can be considered a sink or source of C and how soils can be managed in order to mitigate climate change. However, there is still a lack of knowledge about the contribution of different C sources to soil organic carbon (SOC) formation, particularly in the subsoil. As the subsoil can store approximately as much C as the topsoil, such information is crucial. In a series of studies described in this thesis, data from the Ultuna long-term field experiment established in 1956 were used to study the effects of different organic amendments and mineral fertilizers, which were found to have influenced topsoil and subsoil in several ways. Cultivation of maize, a C₄ crop, began in the experiment in 2000, but prior to that only C₃ crops were grown. By exploiting the natural difference in C isotopic signature between the metabolisms in these two plant types, the role of these two sources in soil organic matter turnover could be quantified. The isotopic composition of C fluxes and stocks in the Ultuna experiment revealed the contribution of different sources to different C pools. Old (>10 years) SOC resulted contributing as much as young (<10 years) SOC to soil respiration. A set of soil respiration measurements with a cavity-ring-down spectrometer directly in the field at different times over the growing season allowed the relative contributions of autotrophic and heterotrophic respiration to be determined. Another set of measurements on soil samples from 0 to 50 cm depth was used to estimate the contribution of different SOC sources within the profile, finding a high contribution of root-derived C on total SOC in the topsoil and upper subsoil. By utilizing the topsoil C isotope and SOC data the root humification coefficient with two different methods could be calculated, suggesting that contribution of root-derived C on total SOC is often underestimated. The measured changes in the δ¹³SOC signature over the years in European bare fallow plots receiving virtually no C input during several decades allowed the natural δ¹³C enrichment occurring in SOC to be measured and modelled. The results validated those of the natural abundance-based techniques over the mid- to short-term. The natural δ¹³SOC enrichment was modelled by calibrating a Rayleigh distillation function. The enrichment kinetic resulted similar in all the sites, and the general calibration could be extended to other studies. This thesis studied the C cycle in a managed long-term field experiment from several perspectives and across different scales, so providing valuable information of potentially high importance for understanding the general dynamics of C in soil. During the 53 years of the Ultuna long-term field experiment, significant differences between the treatments have developed, with clear C accumulation or depletion in soil to 35 cm depth. Thus, SOC changes below ploughing depth should be considered in SOC balance studies and as a viable C sequestration strategy.
|
|
| 7. |
- Menichetti, Lorenzo, et al.
(författare)
-
Organic amendments affect delta C-13 signature of soil respiration and soil organic C accumulation in a long-term field experiment in Sweden
- 2013
-
Ingår i: European Journal of Soil Science. - : Wiley. - 1351-0754 .- 1365-2389. ; 64:5, s. 621-628
-
Tidskriftsartikel (refereegranskat)abstract
- The contribution of young and old soil organic carbon (SOC) pools to soil CO2 fluxes and specific respiration rates of these fluxes was determined by using C-13 signatures in the Ultuna long-term continuous soil organic matter experiment (C-SOME). Initiated in 1956, the experiment had a range of treatments amended organically and with mineral nitrogen fertilizer under C-3 cultivation until 1999, and thereafter under C-4 (maize) cultivation. In 2011, soil respiration was measured in situ prior to planting, during growth and after harvest. The contributions from C-4- and C-3-C as well as their specific respiration rates were estimated from C-13 differences in SOC and CO2 fluxes. The contributions from C-4-C sources were further separated into autotrophic and heterotrophic respiration by comparing respiration rates before and after harvest. Between 165 and 385g C-4-Cm-2 accumulated during 10years of maize growth, contributing between 4.9 and 8.1% to the total SOC stock. Although recent C-4-C had an average specific respiration rate that was 8.4-22.6 times greater than C-3-C, total soil respiration was generally equally split between C-3-C and C-4-C. Both pools are therefore important sources of CO2 in the overall C budget, and a crucial factor in accounting for SOC stock change caused by management. Experimental treatments influenced specific respiration rates of C-4 plant material and accumulation of SOC stock, demonstrating how greater SOC accumulation can be favoured by high-quality C inputs.
|
|
