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Fertilized Soils (fertilized + soil)
Selected AbstractsThe effects of chronic nitrogen fertilization on alpine tundra soil microbial communities: implications for carbon and nitrogen cyclingENVIRONMENTAL MICROBIOLOGY, Issue 11 2008Diana R. Nemergut Summary Many studies have shown that changes in nitrogen (N) availability affect primary productivity in a variety of terrestrial systems, but less is known about the effects of the changing N cycle on soil organic matter (SOM) decomposition. We used a variety of techniques to examine the effects of chronic N amendments on SOM chemistry and microbial community structure and function in an alpine tundra soil. We collected surface soil (0,5 cm) samples from five control and five long-term N-amended plots established and maintained at the Niwot Ridge Long-term Ecological Research (LTER) site. Samples were bulked by treatment and all analyses were conducted on composite samples. The fungal community shifted in response to N amendments, with a decrease in the relative abundance of basidiomycetes. Bacterial community composition also shifted in the fertilized soil, with increases in the relative abundance of sequences related to the Bacteroidetes and Gemmatimonadetes, and decreases in the relative abundance of the Verrucomicrobia. We did not uncover any bacterial sequences that were closely related to known nitrifiers in either soil, but sequences related to archaeal nitrifiers were found in control soils. The ratio of fungi to bacteria did not change in the N-amended soils, but the ratio of archaea to bacteria dropped from 20% to less than 1% in the N-amended plots. Comparisons of aliphatic and aromatic carbon compounds, two broad categories of soil carbon compounds, revealed no between treatment differences. However, G-lignins were found in higher relative abundance in the fertilized soils, while proteins were detected in lower relative abundance. Finally, the activities of two soil enzymes involved in N cycling changed in response to chronic N amendments. These results suggest that chronic N fertilization induces significant shifts in soil carbon dynamics that correspond to shifts in microbial community structure and function. [source] Evaluation of laboratory assays for the assessment of leaching of copper and chromium from ground-contact woodENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2007Ana I. García-Valcárcel Abstract Laboratory studies were conducted to assess the leaching of Cu and Cr from wood, treated with a Cu-Cr-B preservative, when placed in contact with soil. Two laboratory assays were performed: Wood in contact with soil solutions over 30 d, and wood in direct contact with soil over 30 weeks. The influence of several factors, such as soil type and fertilizer use, was studied in both assays. In addition, the effect of soil moisture content and temperature was evaluated when wood was in contact with soil. A discrepancy in the results of the laboratory assays was observed. Leaching of Cu and Cr increased when soil in contact with wood was fertilized, but only an increase of Cu leaching was observed when soil solutions from fertilized soils were used. Moreover, soil solutions from a sandy clay loam soil produced a higher Cu leaching than those from a loamy sand soil, whereas the contrary occurred when treated wood was in direct contact with these soils. In the assay of treated wood in ground contact, the highest metal losses were produced in fertilized soils maintained at constant temperature and high soil moisture content, the latter being the most important factor. These losses were in the range of 5.34 to 15.6% for Cu and 1.85 to 2.35% for Cr in the soils studied. The proposed laboratory assay, using treated wood in direct contact with soil at a moisture content near field capacity during a period of 30 weeks, produced total metal losses that were in accordance with those reported by other authors under field conditions, expressed on a per-year basis. [source] Efficiency of acid phosphatases secreted from the ectomycorrhizal fungus Hebeloma cylindrosporum to hydrolyse organic phosphorus in podzolsFEMS MICROBIOLOGY ECOLOGY, Issue 2 2010Julien Louche Abstract Ectomycorrhizal fungi may improve the phosphate nutrition of their host plants by secreting, into the soil solution, acid phosphatases (AcPases) able to release orthophosphate (Pi) from soil organic phosphorus (Po). Using cation-exchange chromatography, we separated four fractions with AcPase activity secreted by the ectomycorrhizal fungus Hebeloma cylindrosporum grown in a pure culture under P-starved conditions. Each AcPase active fraction displayed strong ability in vitro to hydrolyse a wide range of phosphate monoesters, but none of them efficiently hydrolysed phytate. Their efficiency to release Pi from soil NaHCO3 -extractable Po was studied in a sandy podzol used intact or autoclaved. Soils were collected in a 15-year-old Pinus pinaster stand, receiving regular fertilization or not. Autoclaving increased the NaHCO3 -extractable Po concentrations by 55% in unfertilized and by 32,43% in fertilized soils. The efficiency of each AcPase fraction was affected significantly by the soil fertilization regime and the soil treatment (intact vs. autoclaved). The proportion of labile Po enzyme ranged from 0% to 11% and 14% to 48% after 1 h of incubation in bicarbonate solutions extracted from intact and autoclaved soils, respectively. This work suggests that AcPases secreted from H. cylindrosporum could be efficient in recycling Po pools from soil microorganisms that may be delivered by soil autoclaving. [source] The response of heterotrophic activity and carbon cycling to nitrogen additions and warming in two tropical soilsGLOBAL CHANGE BIOLOGY, Issue 9 2010DANIELA F. CUSACK Abstract Nitrogen (N) deposition is projected to increase significantly in tropical regions in the coming decades, where changes in climate are also expected. Additional N and warming each have the potential to alter soil carbon (C) storage via changes in microbial activity and decomposition, but little is known about the combined effects of these global change factors in tropical ecosystems. In this study, we used controlled laboratory incubations of soils from a long-term N fertilization experiment to explore the sensitivity of soil C to increased N in two N-rich tropical forests. We found that fertilization corresponded to significant increases in bulk soil C concentrations, and decreases in C loss via heterotrophic respiration (P< 0.05). The increase in soil C was not uniform among C pools, however. The active soil C pool decomposed faster with fertilization, while slowly cycling C pools had longer turnover times. These changes in soil C cycling with N additions corresponded to the responses of two groups of microbial extracellular enzymes. Smaller active C pools corresponded to increased hydrolytic enzyme activities; longer turnover times of the slowly cycling C pool corresponded to reduced activity of oxidative enzymes, which degrade more complex C compounds, in fertilized soils. Warming increased soil respiration overall, and N fertilization significantly increased the temperature sensitivity of slowly cycling C pools in both forests. In the lower elevation forest, respired CO2 from fertilized cores had significantly higher ,14C values than control soils, indicating losses of relatively older soil C. These results indicate that soil C storage is sensitive to both N deposition and warming in N-rich tropical soils, with interacting effects of these two global change factors. N deposition has the potential to increase total soil C stocks in tropical forests, but the long-term stability of this added C will likely depend on future changes in temperature. [source] Use of labelled nitrogen to measure gross and net rates of mineralization and microbial activity in permanent pastures following fertilizer applications at different time intervals,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2002David J. Hatch Measurements of some of the main internal N-cycling processes in soil were obtained by labelling the inorganic N pool with the stable isotope of nitrogen (15N). The 15N mean pool dilution technique, combined with other field measurements, enabled gross and net N-mineralization rates to be resolved in grassland soils, which had previously either received fertilizer N (F), or had remained unfertilized (U) for many years. The two soils were subdivided into plots that received N at different time intervals (over 3 weeks), prior to 15N measurements being made. By this novel approach, possible ,priming' effects over time were investigated to try to overcome some of the temporal problems of isotopic labelling of soil N (native plus fertilizer) and to identify possible changes in a range of primary N-transformation processes. The results suggested that an overall stimulation of microbially mediated processes occurred with all N treatments, but there were inconsistencies associated with the release of N, both in the timing and the degree to which different processes responded to the application of fertilizer N. The rates of these processes were, however, within the range of previously reported data and the 15N measurements were not adversely affected by the differences in N pools created by the treatments. Thus, the mean pool dilution technique was shown to be applicable to agricultural soils, under conditions relevant to grass swards receiving fertilizer. For example, between the,U and F treatments, the size of inorganic N pools increased by five-fold and gross rates of mineralization reached 3.5 and 4.8,µg N g,1 (dry soil) d,1, respectively, but did not vary greatly with the timing of N applications. A correlation (r2,=,0.57) was found between soil respiration (which is relatively simple to measure) and net mineralization (which is more time consuming), suggesting that the former might be used as an indicator of the latter. Although this relationship was stronger in previously unfertilized soils, the similarities found with fertilized soils suggest that this approach could be used to obtain information of wider agronomic value and would, therefore, warrant further work under a range of soil conditions. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||