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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 51 (2000), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The spatial heterogeneity of N2O flux at short distances (0.1–2 m) was characterized in relation to various soil physical and chemical properties and the location of incorporated crop residues in arable soils. Plots were prepared with uniform compaction (either zero or compacted by a laden two-wheel-drive tractor) in two field experiments, one under winter barley (Hordeum vulgare), the other under oil-seed rape (Brassica napus). Flux measurements were made of N2O using small chambers (7.3 cm diameter) placed at intervals of approximately 10 cm along a transect (c. 2 m long) across the direction of application of the treatments of compaction and residue incorporation. The flux of N2O and many other measurements showed large variation over short distances, particularly when fluxes were small. The spatial variation of the flux was not closely related to the soil properties. Correlations showed that cone resistance, air permeability and closeness to incorporated residues were as important as soil NO3, NH4 and soluble C in determining flux of N2O from non-compacted soils. Most properties of compacted soils did not correlate with N2O flux. Correlation and multiple regression analysis failed to establish consistent relations between soil environmental variables and N2O flux, but principal component regression indicated that, overall, N2O flux increased with decreasing distance from straw residues and air permeability, and with increasing cone resistance and wet bulk density.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    European journal of soil science 56 (2005), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Soil pore networks have a complex geometry, which is challenging to model in three dimensions. We use a Boolean model of pore space that has proved useful in modelling gas diffusion in dry structures to investigate the distribution of water in this pore space and to quantify the effects on pore connectivity to the soil surface. We first show how total porosity in dry soil influences connectivity via the percolation threshold. Then we show that our model simulation of the ‘ink-bottle effect’ can account for much of the hysteresis of the soil water. The differences in distribution of water between wetting and drying result in maintaining greater connectivity of the air-filled pore space during drying than during wetting. Hysteresis is large at small total porosities and slowly declines as porosity increases. During wetting much pore space is blocked when more than 40% of the pore space is filled with water, although during drying all non-isolated air-filled pores are connected to the surface. Even when soil is allowed to wet to near saturation, there are rapid increases in pore connectivity during drying, which may explain, for example, rapid increases in production and emission of nitrous oxide in soils near saturation.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5036
    Keywords: borescope ; minirhizotron ; pasture ; root length density ; silvopastoral ; wild cherry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A method for counting root intersections with observation tubes (mini- or micro-rhizotrons) is proposed that allows a theoretical conversion of root counts to estimated root length density and which is robust to the effects of tracking along the tubes. A field test showed that the method agreed well with measured root length densities in cores for wild cherry roots but not for roots of pasture species. The circumstances in which the method might be expected to perform well are discussed. Analysis of data from a field trial revealed that root counts were not uniformly distributed around the circumference of the observation tube. Implications for the design of such trials are noted.
    Type of Medium: Electronic Resource
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