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911.
Stephen AC Marklevitz Elizabete Almeida Joanna Flemming Jocelyne Hellou 《Journal of Soils and Sediments》2008,8(2):92-97
Background, Aims and Scope
Our study determined if and when an avoidance or attraction behavioural response would be displayed by Ilyanassa obsoleta when presented with a choice between harbour and reference sediments. Our goal was to develop a non-lethal approach that could be used in future assessments of the environmental quality of field sediments. 相似文献912.
913.
Richard W. Todd N. Andy Cole R. Nolan Clark William C. Rice Wen-Xuan Guo 《Biology and Fertility of Soils》2008,44(8):1099-1102
Cattle feedyards can impact local environments through emission of ammonia and dust deposited on nearby land. Impacts range
from beneficial fertilization of cropland to detrimental effects on sensitive ecosystems. Shortgrass prairie downwind from
an adjacent feedyard on the southern High Plains of Texas, USA changed from perennial grasses to annual weeds. It was hypothesized
that N enrichment from the feedyard initiated the cascade of negative ecological change. Objectives were to determine the
distribution of soil nitrogen and estimate N loading to the pasture. Soil samples were collected from 119 locations across
the pasture and soil total N (TN), nitrate-N and ammonium-N (AN) determined in the top 30 cm. Soil TN concentration decreased
with distance downwind from the feedyard from 1.6 ± 0.2 g kg−1 at 75 m to 1.2 ± 0.05 g kg−1 at 582 m. Nitrate-N concentration decreased within 200 m of the feedyard and changed little at greater distances. Ammonium-N
concentration decreased linearly (P < 0.001) with increasing distance from the feedyard from 7.9 ± 1.7 mg kg−1 within 75 m from the feedyard to 5.8 ± 1.5 mg kg−1 at more than 550 m from the feedyard; however, distance only explained 12% of the variability in AN concentration. Maximum
nitrogen loading, from 75 to 106 m from the feedyard, was 49 kg ha−1 year−1 over 34 years and decreased with distance from the feedyard. An estimate of net dry deposition of ammonia indicated that
it contributed negligibly to N loading to the pasture. Nitrogen enrichment that potentially shifted vegetation from perennial
grasses to annual weeds affected soil N up to 500 m from the feedyard; however, measured organic and inorganic N beyond that
returned to typical and expected levels for undisturbed shortgrass prairie.
相似文献
Richard W. ToddEmail: |
914.
Kannan Iyyemperumal James GreenJr. Daniel W. Israel Noah N. Ranells Wei Shi 《Biology and Fertility of Soils》2008,44(3):425-434
This study characterized soil chemical and microbiological properties in hay production systems that received from 0 to 600 kg
plant-available N (PAN) ha−1 year−1 from either swine lagoon effluent (SLE) or ammonium nitrate (AN) from 1999 to 2001. The forage systems contained plots planted
with bermudagrass (Cynodon dactylon L.) or endophyte-free tall fescue (Festuca arundinaceae Schreb.). In March 2004, the plots were sampled for measurements of a suite of soil chemical and microbiological properties.
Nitrogen fertilization rates were significantly correlated with soil pH and K2SO4-extractable soil C but not with total soil C, soil C/N ratio, electrical conductivity, or Mehlich-3-extractable nutrients.
Soil supplied with SLE had significantly lower Mehlich-3-extractable nutrients than the soil supplied with AN. Two indicators
of soil N-supplying capacity (potentially mineralizable N and amino sugar N) varied with plant species and the type of N fertilizer.
However, they generally peaked at an application rate of 200 or 400 kg PAN ha−1 year−1. Soil microbial biomass C also peaked at an application rate of 200 or 400 kg PAN ha−1 year−1. Nitrification potential was significantly higher in soil supplied with AN than in the unfertilized control but was similar
between SLE-fertilized and unfertilized soils. Our results indicated that an application rate as high as 600 kg PAN ha−1 year−1 did not benefit soil microbial biomass, microbial activity, and N transformation processes in these forage systems. 相似文献
915.
Phosphorus (P) immobilization in soil involves geochemical (e.g., sorption, precipitation, and diffusion) and microbiological
(microbial uptake) processes. Using a Brazilian Ultisol, relative contributions of both processes to the total immobilization
of applied P over 14 days were investigated. The P immobilized by microbes as interpreted by microbial suppression (achieved
by mercury sterilization) was 17, 50, 54, and 56% (of the total immobilized P) on days 3, 7, 10, and 14 after fertilization,
respectively. In the short-term (1 to 3 days), microbes played less of a role than did the physical effect of shaking the
soil, but became the major factor by days 7 to 14. Geochemical process that might be considered short-term ageing caused only
13–16% of the total immobilization in the same time period above. Calculations supported the interpretation that measurable
diffusion occurred across water films on the soil particles. 相似文献
916.
Leguminous leys are important sources of nitrogen (N), especially in forage-based animal production and organic cropping.
Models for estimating total N2 fixation of leys—including below-ground plant-derived N (BGN)—are based on grazed or harvested leys. However, green manure
leys can have different proportions of above-ground plant-derived N (AGN) and BGN when subjected to different cutting regimes.
To investigate the effects of cutting on N distribution in white clover, a pot experiment was carried out using 15N techniques to determine N2 fixation, N rhizodeposition and root C and N content of cut and uncut white clover (Trifolium repens L. cv. Ramona) plants. Percentage N derived from air (%Ndfa) was lower in uncut (63%) than in cut (72%) plants, but total
Ndfa was not significantly affected by cutting. The higher reliance on N2 fixation in cut plants was thus counterbalanced by lower biomass and total N content. With BGN taken into account, total
plant-derived N increased by approximately 50% compared with AGN only. Cutting did not affect the proportion of BGN to standing
shoot biomass N after regrowth, but decreased the proportion of BGN to total shoot biomass production during the entire growth
period. Thus, estimates of N fixation in green manure leys should consider management practices such as cutting regime, as
this can result in differences in above- and below-ground proportions of plant-derived N. 相似文献
917.
Valéria Marino Rodrigues Sala Elke Jurandy Bran Nogueira Cardoso Fabiana Fantinatti Garboggini Neusa de Lima Nogueira Adriana Parada Dias da Silveira 《Biology and Fertility of Soils》2008,44(8):1107-1112
This study reports for the first time the presence of diazotrophic bacteria belonging to the genera Achromobacter and Zoogloea associated with wheat plants. These bacterial strains were identified by the analysis of 16S rDNA sequences. The bacterium
IAC-AT-8 was identified as Azospirillum brasiliense, whereas isolates IAC-HT-11 and IAC-HT-12 were identified as Achromobacter insolitus and Zoogloea ramigera, respectively. A greenhouse experiment involving a non-sterilized soil was carried out with the aim to study the endophytic
feature of these strains. After 40 days from inoculation, all the strains were in the inner of roots, but they were not detected
in soil. In order to assess the location inside wheat plants, an experiment was conducted under axenic conditions. Fifteen
days after inoculation, preparations of inoculated plants were observed by the scanning electron microscope, using the cryofracture
technique, and by the transmission electron microscope. It was observed that all isolates were present on the external part
of the roots and in the inner part at the elongation region, in cortex cells, but not in the endodermis or in the vascular
bundle region. No colonizing bacterial cells were observed in wheat leaves. 相似文献
918.
An experiment was conducted to investigate the effects of earthworm (Metaphire guillelmi) activities on rice photosynthates distribution in plant–soil system through 14C pulse-labelling method. Rice was planted in pots, and maize straw was mulched on the surface with or without earthworms.
Rice plants at tillering stage or heading stage were labelled with 14CO2. Plant and soil were sampled 15 days after labelling at the tillering or heading stage and at harvest. Rice growth was inhibited
by earthworms (M. guillelmi) at early stage, but the inhibition disappeared at later stage. Earthworms significantly (P < 0.01) increased the 14C percentage in root at day 15 after tillering stage labelling, but the effect disappeared at harvest. Earthworms (M. guillelmi) significantly (P < 0.01) increased the 14C percentage in root at day 15 after heading stage labelling and increased 14C percentage in soil at harvest. Earthworms decreased the percentages of total organic 14C (TO14C) present as microbial biomass 14C (MB14C) and increased the percentages of total organic 14C present as dissolved organic 14C (DO14C) at all sampling times. It is suggested that earthworms might alter the transfer of plant photosynthates from the aboveground
to the belowground, and thus, soil active C pool. However, these data should be also confirmed in the field. 相似文献
919.
Sara Sánchez-Moreno Sean Smukler Howard Ferris Anthony T. O’Geen Louise E. Jackson 《Biology and Fertility of Soils》2008,44(5):727-744
The aim of this paper was to assess biodiversity among different habitats of an organic farm and the relationships between
some soil properties, nematode taxonomic diversity, and soil food web condition. Eight habitats were studied in the farm:
ponds, ditches, a riparian corridor, hedgerows, and four agricultural fields (mustard, oats, fallow, and legumes). The undisturbed
riparian corridor had higher soil and concentrations, and potentially mineralizable N and higher abundances of bacterivore nematodes and longer food webs. Canonical
correlation analysis showed associations between habitats and nematode trophic groups: predatory and bacterial-feeding nematodes
in the riparian corridor and hedgerows, omnivore nematodes in the ponds and ditches, and fungal-feeding nematodes in the legume
field. Soil chemical and physical properties mirrored the aboveground farm patterns and were more similar among habitats that
were or had been cultivated, compared to the riparian corridor. Soil food web indices, based on functional analysis of nematode
faunal composition, reflected the aboveground landscape heterogeneity. Discriminant analysis indicated that soil food web
indices separated the two most disturbed habitats (ponds and tailwater ditches) from the two least disturbed habitats (the
riparian corridor and hedgerows). The indices correlated with soil functioning as inferred by soil properties. Abundance of
nematode taxa was not associated with aboveground landscape patterns. The complexity of the soil food web may have been influenced
by (1) environmental factors that differed between years, (2) different time periods since disturbance in the various habitats,
and (3) movement of nutrients and organisms by water flow between habitats in the farmscale. 相似文献
920.
Saman Bowatte Russell Tillman Andrew Carran Allan Gillingham David Scotter 《Biology and Fertility of Soils》2008,44(6):805-813
This paper explored the potential of application of in situ ion exchange resin membrane (IEM) technique for assessing soil
nitrogen (N) availability and spatial distribution in New Zealand grazed pastures. Field and incubation experiments conducted
to test the technique proved IEM technique to be a useful approach to monitoring the continuous changes in soil mineral N
in pasture soils. The field testing showed that the IEM technique reflects both differences in pool size and mineral N flux,
while 2-M KCl extraction reflects only pool size at the sampling. Testing the effects of residence time, temperature, soil
inorganic N content, and soil water content through diffusion modeling offers further support for using IEM to explore the
complex dynamics of nitrogen availability in pasture soils. 相似文献