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[Effects of phenoxy carboxylic acid herbicides on plant photosynthetic and soil microbiological activities].

Lontrele and cowboy were tested for effects on the photosynthetic activity of amaranthus and the microbiological activity of leached chernozem. The tested herbicides were shown to be beneficial for different changes occurring in the levels of total chlorophyll in the amaranthus leaves and for the leached chernozem to evolve carbon dioxide in different phases of amaranthus growth.

Amaranthus↗
PubMed2001

Aspects of Marker/Reporter Stability and Selectivity in Soil Microbiology.

Based on several experiences of microbial release using genetically modified Rhizobium leguminosarum, we have highlighted a number of aspects related to the suitability of introduced markers such as resistance to mercury and b-galactosidase activity, the latter serving the function of high-expression level reporter gene obtained by the introduction of a synthetic promoter conferring strong inducible expression in Gram-negative bacteria. In vitro expression and in vivo performances of the chosen examples have been followed in model strains comparing gene dosage and expression levels. The technical possibility of unambiguously monitoring the marked GMM has been evaluated in medium- and long-term experiments carried out both in microcosms and soil, also including the presence of the plant symbiotic host. Marker stability, regardless the nature of the gene, was shown to be dependent on the location of the genetic modification and on its degree of gene expression regulation. Reporter strength was found to be an advantage allowing the distinction of marker-bearing bacteria while negatively affecting their genetic stability. Plasmid-borne regulated reporters were found to be stable up to the stages of rhizosphere colonization, but were more critically selected against upon symbiotic host invasion.

Journal Article↗
PubMed2002

[Responses of agricultural crops of free-air CO2 enrichment].

Over the past decade, free-air CO2 enrichment (FACE) experiments have been conducted on several agricultural crops: wheat(Triticum aestivum L.), perennial ryegrass (Lolium perenne), and rice(Oryza sativa L.) which are C3 grasses; sorghum (Sorghum bicolor (L.) Möench), a C4 grass; white clover (Trifolium repens), a C3 legume; potato (Solanum tuberosum L.), a C3 forb with tuber storage; and cotton (Gossypium hirsutum L.) and grape (Vitis vinifera L.) which are C3 woody perennials. Using reports from these experiments, the relative responses of these crops was discussed with regard to photosynthesis, stomatal conductance, canopy temperature, water use, water potential, leaf area index, shoot and root biomass accumulation, agricultural yield, radiation use efficiency, specific leaf area, tissue nitrogen concentration, nitrogen yield, carbohydrate concentration, phenology, soil microbiology, soil respiration, trace gas emissions, and soil carbon sequestration. Generally, the magnitude of these responses varied with the functional type of plant and with the soil nitrogen and water status. As expected, the elevated CO2 increased photosynthesis and biomass production and yield substantially in C3 species, but little in C4, and it decreased stomatal conductance and transpiration in both C3 and C4 species and greatly improved water-use efficiency in all the crops. Growth stimulations were as large or larger under water-stress compared to well-watered conditions. Growth stimulations of non-legumes were reduced at low soil nitrogen, whereas elevated CO2 strongly stimulated the growth of the clover legume both at ample and under low N conditions. Roots were generally stimulated more than shoots. Woody perennials had larger growth responses to elevated CO2, while at the same time, their reductions in stomatal conductance were smaller. Tissue nitrogen concentrations went down while carbohydrate and some other carbon-based compounds went up due to elevated CO2, with leaves and foliage affected more than other organs. Phenology was accelerated slightly in most but not all species. Elevated CO2 affected some soil microbes greatly but not others, yet overall activity appears to be stimulated. Detection of statistically significant changes in soil organic carbon in any one study was impossible, yet combining results from several sites and years, it appears that elevated CO2 did increase sequestration of soil carbon. Whenever possible, comparisons were made between the FACE results and those from prior chamber-based experiments reviewed in the literature. Over all the data and parameters considered in this review, there are only two parameters for which the FACE- and chamber-based data appear to be inconsistent. One is that elevated CO2 from FACE appears to reduce stomatal conductance about one and a half times more than observed in prior chamber experiments. Similarly, elevated CO2 appears to have stimulated root growth relatively more than shoot growth under FACE conditions compared to chamber conditions. Nevertheless, for the most part, the FACE- and chamber-based results have been consistent, which gives confidence that conclusions drawn from both types of data are accurate. However, the more realistic FACE environment and the larger plot size have enabled more extensive robust multidisciplinary data sets to be obtained under conditions representative of open fields in the future high-CO2 world.

Air↗
PubMed1992

Mathematical descriptions of accelerated transformation of 1,3-dichloropropene in soil; a microbiological assessment.

The rate of transformation of the soil fumigant (Z)-and (E)-1,3-dichloropropene in moist soil layers was measured at incubation temperatures of 5 degrees C, 10 degrees C and 20 degrees C. 'DD95' was added to four characterized soil layers, in amounts corresponding to realistic field contents after fumigation. Rapid transformation immediately after application was observed in layers with low initial contents (30-300 micrograms/kg dm) and could well be described with a first-order rate model. Incubation at higher doses (5-15 mg/kg dm respectively) showed distinctly different transformation pathways. Degradation curves could well be computed using a microbiological interspective competition (MIC) model for moist soil. The transformation rate is inversely correlated to microorganism population size and growth. Transformation curves described by MIC are characterized by a lag-time, a period of accelerated transformation and a period of decreasing transformation rates. At low temperatures, DT50 values of more than 20 days could be observed. First-order rate computations did not exceed 8 days. The use of different mathematical discriptions for various soil layers and soil temperatures permits simulation of DD95-transformation by microorganisms in the soil profile throughout the growing season.

Allyl Compounds↗
PubMed2005

Enhancing bioremediation of diesel oil and gasoline in soil amended with an agroindustry sludge.

This paper presents a study of the bioremediation of diesel oil and gasoline by a series of controlled laboratory tests. Sludge from an agroindustry was used to enhance bioremediation of both gasoline and diesel oil mixed with a soil mass to compare its efficiency with that of a mineral fertilizer. Effects of soil microbiology and soil mixtures were investigated by means of evolution of CO2, microorganism populations at 90 days, pH at 65 and 95 days, mineral nitrogen, and gas chromatographic analysis of the benzene, toluene, methyl tertiary butyl ether, C8, and C9+total aromatics at the end of the experiments. Treatments containing sludge showed better soil conditions after 170 days of treatment (inorganic nitrogen and microbiota activity) compared with gasoline and diesel oil without amendments. Samples had no detectable traces of the measured hydrocarbons at 170 days of treatment.

Agriculture↗
PubMed2005

[Effects of different de-farming and reafforestation patterns on changes of soil fertility quality in Karst region of southwestern China].

A ten-year fixed site harnessing was conducted in the severely eroded karst region of Ziyun County, Guizhou Province by adopting four different de-farming and reafforestation patterns, and the properties of soil chemistry, soil microbiology, and soil enzymology after harnessing were determined in 2003. The results showed that the total amount of soil microbes and the individuals of bacteria, fungi and actinomyces were increased obviously, the activities of soil hydrolytic and oxidoreductive enzymes and the soil respiration rate enhanced evidently, and the storage of soil nutrients as well as their supplying intensities promoted pronouncedly, demonstrating that the soil quality in all adopted patterns was improved in varying degrees. The values of soil integrated fertility index (IFI) had an increasing trend. Therefore, proper biological measures and essential supplementary engineering measures were effective in improving the soil fertility quality of severely degraded karst region.

China↗