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1.
Abstract

Conventional methods for labeling of legume residues with 15N for the measurement of the transfer of nitrogen (N) to a succeeding crop are inadequate for zero‐tillage management where the residue is chemically desiccated. The study tests the feasibility of in situ labeling of legumes with 15N for the study of N transfer to a succeeding crop. A single foliar application of 15N‐labeled urea was misted onto the stems and leaves of second cut red clover and alfalfa in the field in 0.75 x 0.75 m microplots. Nitrogen content and 15N enrichment were determined for above‐ and below‐ground plant parts. Overall, recovery of the foliar applied 15N in the forage was 30% and 57% for the alfalfa and red clover, respectively. Of the nitrogen recovered, approximately 70% and 30% were recovered in the above‐ and below‐ground plant parts, respectively, for both forage species. Atom % 15N was similar for the red clover and alfalfa for each of the above‐ground plant parts and was slightly lower in the crown and roots for the red clover than for the alfalfa. Values of atom % 15N ranged from 0.5 for fine roots to 1.5 for leaves above 0.20 m from the ground. Labeling of the plant material was not uniform between plant parts but was adequate for many studies of N transfer to a succeeding crop.  相似文献   

2.

Purpose  

Risks associated to “heavy metals” (HM) soil contamination depend not only on their total content but, mostly, on their mobility. Many extraction procedures have been developed to evaluate HM mobility in contaminated soils, but they are generally time consuming (especially the sequential extraction procedures (SEPs)) and consequently applicable on a limited number of samples. For this reason, a simple screening method, applicable even “in field”, has been proposed in order to obtain a rapid evaluation of HM mobility in polluted soils, mainly focused on the fraction associated to Fe and Mn oxide/hydroxides.  相似文献   

3.
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4.
A new inorganic phosphorus (IP) fractionation scheme developed by Jiang and Gu was used in an incubation experiment to investigate the transformation of applied P in a calcareous fluvisol. The results show that after addition of common superphosphate (CSP), the Ca2-P in the soil decreased gradually and transformed largely to the less available Fe-P, Al-P and Ca8-P, rather than to the unavailable forms of Ca10-P and O-P. The different IP fractions ranked in the following order with respect to the increment by addition of CSP after 120 days of incubation: Fe-P> Al-P>Ca8-P>Ca2-P. After addition of pig manure, the content of Ca2-P in the soil increased rapidly at first and then decreased slowly, and the amount of different IP fractions accumulated after 120 days of incubation ranked in the following order: Ca2-P > Fe-P > Ca8-P > Al-P.  相似文献   

5.
This study is the first approach to evaluate the diversity of bacterial β-glucosidase-encoding gene sequences, aiming to identify the main environmental factors structuring bacterial β-glucosidase genetic diversity in semiarid soils. Two agricultural management systems, soils under spontaneous cover vegetation vs. noncovered herbicide-treated soils, were tested. The weed biomass generated in the former was estimated around 2,600 kg?ha?1?year?1, whereas leaves and root exudates from olive trees were the only input of C biomass in the latter. Dendrograms generated from polymerase chain reaction–denaturing gradient gel electrophoresis profiles of bacterial β-glucosidase-encoding genes revealed two clusters determined by soil treatment and sharing <20 % similarity. The sequences of a total of 59 DNA fragments, representing 39 operational taxonomic units, were successfully determined. The Proteobacteria phylum clearly dominated all the soil samples, but representatives of Chloroflexi, Deinococci, Actinobacteria, Thermotogae, and Firmicutes class were also detected. Management strategies favoring the presence of spontaneous vegetation determined a higher genetic diversity of β-glucosidase-encoding genes of soil bacteria. However, since there is little information of β-glucosidase gene sequences available in databases, it is difficult to establish particular relationships between bacterial networks for C degradation and land use. Results from canonical correspondence analysis indicated that bacterial metabolic networks for oligomeric C substrates utilization were affected by the physicochemical properties of the soil; the uppermost 10 cm of covered soil clustered together and were positively correlated with some chemical properties related to soil fertility, whereas less influence of soil texture was observed for the deeper layers of bare soils.  相似文献   

6.
The methods based on N uptake of aerial-plants, soil organic matter （SOM） dynamics, Jenny＇s equation, and actual measurement of long-term field experiments in Jiaxing, Quzhou, Huangyan and Hangzhou of Zhejiang Province, China were used to determine the organic mineralization rate being helpful in estimating the organic requirement for SOM equilibrium. The results showed that the estimated mineralization ratios of SOM for Jiaxing and Quzhou were, respectively, 0.0404 and 0.0508 based on N uptake of aerial-plants in non-fertilized plots; 0.0405 and 0.012 using SOM dynamics in non-fertilized plots; and 0.0413 and 0.0513 using the actual investigated data and Jenny＇s equation. With Jenny＇s equation, soil organic C balance in manure ＋ N-P-K plots was estimated at nearly 28.8 g kg^-1 for Jiaxing and 32.4 g kg^-1 for Quzhou with predicted SOM linearly related to the actual investigated values （r^2 = 0.9640 for Jiaxing and 0.8541 for Quzhou）. To maintain the SOM balance in the non-fertilized plots the recommended rate of organic materials was 3 000-6 600 kg ha^-1, and the relevant rates of farm yard manure （FYM） in the manure and N-P-K plots were estimated at 3 375 （dry） and 17670 kg ha^-1 （wet） for Jiaxing, 1845 （dry） and 6090 kg ha^-1 （wet） for Quzhou.  相似文献   

7.
Pedology, or the study of soil, is often viewed focusing on soil formation, morphology, mapping and classification. But the study of soil has largely expanded beyond these four areas and now includes quantitative studies using soil legacy data combined with technological advances in data collection, soil sampling and computation. We have global availability of soil information and can retrieve pedological information for any location including some indication of its accuracy. Scientific and technological developments in pedology have been led by the rise of several subdisciplines including pedometrics, digital soil mapping, spectral pedology, digital soil morphometrics, hydropedology, microbial pedology, astropedology and the development of pedotransfer functions. With the expansion of pedology and its relevance for understanding the earth system and tackling global change, it is postulated that soil science has now entered the ‘Pedocene’—a soil epoch equivalent to the Anthropocene. The Pedocene is characterized by the quantitative understanding and evaluation of the global soil system, and the effects of human-induced changes brought to soil.  相似文献   

8.
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9.
Conservation is increasingly central to the botanic garden mission. Living plant collections are important components of conservation. Critical evaluation of living conservation collections with population genetic analysis can directly inform ex situ conservation strategy. Here, we quantify the degree of genetic variation captured through a population-based collection protocol, and explore optimal sampling for ex situ conservation. An extensive living collection derived from one population of Leucothrinax morrisii (Arecaceae) provided a model system. We compared 58 specimens from the ex situ collection with 100 individuals from throughout the parent population via 6 ISSR loci. Random bootstrapped resamples of the data were made to model differently structured ex situ collections. Mean diversity (He) differed little between the collection (0.204) and the population (0.216), and genetic distance (D) was very close (0.036). Very few private alleles were found between the collection and the population. Allelic capture, as measured by percent of private alleles, was greater than 94%. Resampled collections of different sizes captured from 48% to 94% of alleles. Pairwise comparison of bootstrapped resamples suggests that increasing the representation of half-sibling groups does not significantly increase allele capture. Increase in allele capture with increasing sample size is greatest at low resample sizes, and showed diminishing returns as resample size increased. No appreciable increase in allele capture was gained through maintaining different half-sibling groups. These data inform sampling for ex situ conservation purposes, and recommend sample sizes of at least 15 individuals, with the upper limit based on resources.  相似文献   

10.
The antioxidant capacity of methanol and ethanol seed extracts from Euterpe oleracea Mart. (a?aí) against the reactive oxygen species (ROS) peroxyl radicals, peroxynitrite, and hydroxyl radicals was studied with the total oxidant scavenging capacity (TOSC) assay in a modified and automated version. Cold methanol digestion was the most efficient extraction method with respect to the antioxidant capacity. The extracts exhibit good antioxidant capacity against peroxyl radicals, similar to the capacity of the pulp. The antioxidant capacity against peroxynitrite and hydroxyl radicals is even higher. The main antioxidants identified by HPLC-MS and HPLC-CEAD are five different procyanidins (di- through pentamers); furthermore, protocatechuic acid and epicatechin were identified as minor compounds. Determination of TOSC values of HPLC seed extract fractions indicates that the procyanidins contribute substantially to the overall antioxidant capacity. In addition, however, other compounds that have not yet been identified are responsible for a large part of the observed antioxidant capacity.  相似文献   

11.
Direct microscopic observation of microorganisms is an important tool in many microbial studies. Such observations have been reported for Protozoa, fungi, inoculated bacteria, and rhizosphere microorganisms but few studies have focused on indigenous bacteria and their spatial relationship within various microhabitats. Principles and applications of epifluorescence microscopy and confocal laser scanning microscopy for visualization of soil microorganisms in situ are reviewed. Both cationic and anionic dyes (also commonly referred to as fluorochromes if they are fluorescent) have been used based on their ability to bind to specific cellular components of microbial cells. Common fluorochromes used for imaging of microbial cells include acridine orange, ethidium bromide, fluorescein isothiocyanate, 5-(4,6-dichlorotriazinyl) aminofluorescein, 4,6-diamidino-2-phenylindole, europium chelate, magnesium salt of 8-anilino-1-naphthalene sulfonic acid, and calcofluor white M2R. Combining fluorescence staining techniques with soil thin section technology allows one to obtain images of microorganisms in situ. Soil texture and the procedures used for resin embedding are important factors affecting the quality of stained soil thin sections. Indeed, general limitations of applying fluorescence microscopy to soil ecological studies are the non-specific binding of dyes to the soil matrix and the autofluorescence of some soil components. The development of fluorescent in situ hybridization and confocal laser scanning microscopy techniques provides new potential for microbial distribution studies.  相似文献   

12.
Abstract

A representative grassland soil of the lowland areas of the Flooding Pampa (Argentina) was sampled to study the dynamics of the non‐exchangeable ammonium under waterlogging conditions. Most of the external factors determining fixed ammonium release and fixation were considered. There was no net release of ammonium from the clay fixing‐sites to the soil solution, when this soil was flooded under laboratory conditions. We conclude that the non‐exchangeable ammonium fraction in this soil is very stable and with little importance as a nitrogen source for plants.  相似文献   

13.
A sandy soil was amended with different types of sewage sludge (digested, dried, and composted) and pig slurry. The composted sludges displayed higher organic‐matter stability (39–45%) than only digested sludge (26–39%) or digested + dried sludge (23–32%). The microbial biomass of the dried sludge was undetectable. Digested and composted sludges and pig slurry displayed microbial biomasses (12492–13887 µg g?1, 1221–2050 µg g?1, and 5511 µg g?1, respectively) greater than the soil (108 µg g?1). The wastes were applied at seven doses, ranging from 10 to 900 g kg?1. Soils were incubated for 28 days. Substrate‐induced respiration (SIR) was measured for 12 consecutive hours on day 1 and on day 28. The results showed that SIR increased with the dose of organic amendment. However, SIR decreased when moderate doses of pig slurry or high doses of digested + dried sludge were tested. The possibility of using this inhibition as an ecotoxicological indicator is discussed.  相似文献   

14.

Purpose

The study was carried out in a wetland of the Middle Paraná River system, Argentina, in order to evaluate the processes associated with the decomposition of manure, which includes changes in chemical composition, nutrient release of manure, and colonization of invertebrates. We also compared the invertebrate assemblage that colonized manure with that present in the benthos of the wetland.

Materials and methods

Nylon bags were filled with fresh cattle manure and anchored to the littoral zone of the wetland. Six bags were collected after 1, 2, 6, 14, 21, 28, 33, 55, and 79 days: three for invertebrate determination and the other three bags for determination of dry mass and chemical analyses. The nutrient content, cellulose, lignin, and total phenolic compounds of manure were determined. In addition, the leachate of manure was collected for nutrient analyses. Samples of the wetland benthic sediment were collected for benthic invertebrate determination and particle size analyses. Spearman rank correlation was used to evaluate the relationship between chemical compounds of manure and breakdown rate. Principal component analysis was used to explore invertebrate assemblage composition of manure and sediment during the experiment.

Results and discussion

Limnodrilus, Dero, and Chironomus were dominant in the manure. Gatherer-collector was the dominant group in the manure, comprising almost 95 % of the total density of invertebrates. Breakdown rate was significantly related with nutrients, cellulose and total phenolics of manure. An ordination plot showed changes in invertebrate assemblages of manure and sediment samples over time.

Conclusions

This study provides new insight on the importance of manure as a substrate for macroinvertebrate colonization. Cattle manure needs to be considered as a potential source of nutrients for aquatic systems and a substrate for invertebrate assemblages.
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15.
Journal of Soils and Sediments - The unsustainable use of soil natural capital and ecosystem services is of global concern due to damage and losses on a worldwide scale. This situation is further...  相似文献   

16.
The effects on two‐week‐old plants of a salt‐tolerant line (Euroflor) and a salt‐sensitive (SMH‐24) line of sunflower, of varying sodium/calcium (Na/ Ca) ratios in a saline growth medium were assessed after three weeks growth in sand culture under greenhouse conditions. The different Na/Ca ratios of the salt treatment were 36.5, 74.0, and 149, at a constant concentration of 150 mol m‐3 NaCl. Euroflor was superior to SMH‐24 in fresh and dry matters of shoots and roots at varying external Na/Ca ratios. The leaf Na+ concentration in SMH‐24 increased consistently with increase in external Na/Ca ratio, whereas that in Euroflor remained almost unaffected. Although leaf chlorine (Cl‐) was significantly greater in SMH‐24 than Euroflor, there was no effect of decreasing Ca2+ concentration of the saline growth medium on the leaf Cl‐ concentrations of both lines. The lines did not differ in K+, Ca2+ or Mg2+ concentrations of both shoots and roots. The leaf K/Na and Ca/ Na ratios, K versus Na selectivity were considerably higher in Euroflor than in SMH‐24. The lines also did not differ in leaf water potential and gas exchange and these variables were not affected due to decreasing Ca2+ concentration of the saline growth medium. Stomatal conductance and transpiration remained unchanged in Euroflor, whereas those in SMH‐24 decreased significantly at the highest external Na/Ca ratio. Euroflor had significantly greater stomatal conductance and transpiration than those of SMH‐24 at almost all external Na/Ca ratios, whereas the reverse was true for water use efficiency. It was established that Euroflor was tolerant to low Ca2+ concentrations of the saline growth medium as compared with SMH‐24. This was mainly attributable to accumulation of relatively low Na+ and Cl‐ in the leaves, and maintenance of high leaf K/Na and Ca/Na ratios and K versus Na selectivity in Euroflor.  相似文献   

17.
The dependence of the level of contamination of the upper horizon of Al–Fe-humus podzols (Podzols Rustic) with heavy metals (Ni, Cu) on the distance from the Severonickel smelter (Monchegorsk, Murmansk oblast) was studied on a number of test plots in the medium-aged pine stands. It was found that metal concentrations in the soils could be reasonably approximated by the negative exponential function. In the buffer zone of the smelter, the concentrations of Ni and Cu exceed background values by 8–17 times; in the impact zone, by 50–100 times. The study of the dynamics of acid-soluble forms of Ni and Cu in the organic horizons of podzols on the key plots showed that the boundaries of polluted territory shift towards background regions despite the recent five–eightfold decrease in the emissions. The concentrations of heavy metals in the litter horizons continued to increase in the buffer zone. In the impact zone, their contamination remained at the very high level. Firm bounding of heavy metals in the organic horizon coupled with their continuing aerial input did not allow the beginning of the soil self-purification process, which might last for decades and centuries. Raster electron microscope and X-ray spectral microanalysis showed that particles (>85%) of the ashed matter of organic horizons from the background region, the buffer zone, and the impact zone is mainly represented by various soil-forming minerals and iron oxides (in particular, magnetite). In the samples from the impact zone, about 5% of the mineral particles had the surface morphology and chemical composition typical of dust particles emitted into the air by metal smelters. Most probably, these spherical particles represented magnetite Fe3O4 enriched in heavy metals (Cu, Ni).  相似文献   

18.
The distance at which animals flee an approaching predator is known as the ‘flight initiation distance’ (FID). Wildlife managers use FID to develop buffer zones to reduce human impacts on wildlife. Many variables have been demonstrated to influence FID leading one to question whether it can be viewed as a species-specific trait. We tested this critical assumption for developing buffer zones by experimentally approaching eight species of shorebirds found at six sites around Botany Bay, 15 km south of Sydney, Australia. Botany Bay encompasses a range of human impacted areas, from urban developments with high levels of human presence, through to National Parks and wildlife protection areas where human presence is significantly lower. We found that both species and site influenced the distance birds flew away from an approaching human. Importantly, however, there was no significant statistical interaction between site and species demonstrating that ‘flighty’ species were consistently flighty while more tolerant species were consistently tolerant. Taken together, these results suggest that FID can therefore be viewed as a species-specific trait for these shorebirds. The great variability in FID suggests that wildlife managers should be somewhat conservative in developing buffer zones, but they can use previously published FID data for a given species as guidelines for setting buffer zones.  相似文献   

19.
A new, strong base, macro-porous anion exchange resin, Amberlite IRA 996, appeared to be more nitrate selective than sulfate selective in treating high nitrate concentrations (18 mg NO inf3 sup? -N L?1) in potable water. When regeneration is carried out in a closed circuit in which a biological denitrification reactor is incorporated to remove nitrate from the regenerant, regeneration salt requirement and brine production can be minimized. In this combination of ion exchange and biological denitrification, regeneration with 30 g NaHCO3 L?1) is possible in 6 hr at a flow rate of 11 BV hr?1. Accumulation of sulfate in the closed regeneration circuit does not affect the nitrate capacity of the resin.  相似文献   

20.
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