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  • nitrogen availability  (2)
  • 1
    ISSN: 1573-5036
    Keywords: cattle slurry ; nitrogen availability ; nitrogen immobilization ; pig slurry ; ryegrass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ryegrass was grown, in pots under controlled-environment conditions, on soil mixed with each of ten slurries, eight from dairy farms and two from pig farms. In addition, ryegrass was grown under the same conditions but with the water-insoluble material separated from each slurry. Incorporation of the whole slurries increased the yield of herbage, the concentration of N in the herbage and N uptake, compared with plants grown on soil alone, the effects being greatest at the first of six successive harvests. In contrast, incorporation of the water-insoluble material of the cattle slurries decreased herbage yield and N uptake, particularly at the first harvest, but the water-insoluble material of the pig slurries produced some increase in herbage yield and N uptake. The results indicate that the water-insoluble material of the cattle slurries immobilized N that would otherwise have been available from the water-soluble fraction of the whole slurries and/or from the soil. The recovery by the ryegrass of the water-soluble N from the whole slurries was closely correlated with the concentration of N in the water-insoluble material (r=0.863***) and negatively correlated with the C∶N ratio (r=0.892***). Correlations between the recovery of the water-soluble N and the concentrations of N in five particle size fractions of the water-insoluble material indicated that the fraction of smallest particle size (〈0.2 mm) had the greatest effect.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 112 (1988), S. 155-165 
    ISSN: 1573-5036
    Keywords: macro-organic matter ; nitrogen availability ; nitrogen fractionation ; soil nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The available N of 27 soils from England and Wales was assessed from the amounts of N taken up over a 6-month period by perennial ryegrass grown in pots under uniform environmental conditions. Relationships between availability and the distribution of soil N amongst various fractions were then examined using multiple regression. The relationship: available soil N (mg kg−1 dry soil)=(Nmin×0.672)+(Ninc×0.840)+(Nmom×0.227)−5.12 was found to account for 91% of the variance in available soil N, where Nmin=mineral N, Ninc=N mineralized on incubation and Nmom=N in macro-organic matter. The N mineralized on incubation appeared to be derived largely from sources other than the macro-organic matter because these two fractions were poorly correlated. When availability was expressed in terms of available organic N as % of soil organic N (Nao) the closest relationship with other soil characteristics was: Nao=[Ninc×(1.395−0.0347×C∶Nmom]+[Nmom×0.1416], where C∶Nmom=C∶N ratio of the macro-organic matter. This relationship accounted for 81% of the variance in the availability of the soil organic N. The conclusion that the macro-organic matter may contribute substantially to the available N was confirmed by a subsidiary experiment in which the macro-organic fraction was separated from about 20 kg of a grassland soil. The uptake of N by ryegrass was then assessed on two subsamples of this soil, one without the macro-organic matter and the other with this fraction returned: uptake was appreciably increased by the macro-organic matter.
    Type of Medium: Electronic Resource
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