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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 13 (1997), S. 0 
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. This paper reports results from a four year study to investigate the suitability of porous ceramic cups to measure solute leaching on shallow chalk soils. Measurements were carried out in one field following surface applications of nitrate and bromide tracers and in two fields after only bromide was applied. Soil water samples were collected from porous cups at 30,60 and 90cm depth after every 25 mm of drainage, and soil samples from 0–30, 30–60 and 60–90 cm were collected monthly eachwinter. Soil matric suctions andvolumetric moisture content were measured in one winter. Leaching losses, measured with ceramic cups were compared with those measured by soil analysis. Porous cups installed in chalk at 60 and 90 cm depth were only able to collect samples regularly when soil matric suctions were less than 15 kPa. Water held at such low suctions is likely to move quickly through relatively large fissures in the chalk. The slow rate of equilibration between solute concentrations in water moving in macrofissures and those in water moving through micropores of the chalk matrix, means that porous cups may not provide good estimates of leaching losses if they are installed in chalk rock.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 14 (1998), S. 0 
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. The effect of nitrogen fertilizer inputs to cereal crops on nitrate leaching after harvest was tested on 21 experiments on sandy soils in England. At small nitrogen fertilizer rates leaching increased very little with increasing inputs, while at high rates more than half of any additional nitrogen could be accounted for as increase in nitrate leached. In many cases the response fitted two straight lines. Nitrogen offtake in grain also fitted two straight lines, with a form which complemented the leaching response. The gradient averaged 0.52 kg N in grain for every additional 1kg N applied below the break point, but only 0.05 kg/kg above. The break points were generally close to or above the economic optimum N input. The effect of inputs on leaching could he quantitatively related to nitrogen offtake in grain, assuming a constant ratio of nitrogen in grain to total nitrogen uptake. The results show that fields receiving N inputs in excess of the economic optimum cause a disproportionately large nitrate loss. However because of uncertainty in predicting the break point in advance, modest further reduction in leaching will occur by reducing inputs to somewhat below the expected economic optimum.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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