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  • 15N  (1)
  • N use efficiency  (1)
  • 1
    ISSN: 1432-0789
    Keywords: Key words Acid soil ; Brazilian Amazonia ; N use efficiency ; Priming effect ; Oryza sativa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The objective of this study was to determine the efficiency of two N fertilizers, (NH4)2SO4 and urea, for rice (Oryza sativa L.) and rye-grass (Lolium multiflorum L.) cultivated in an Ultisol of central Amazonia using 15N as a tracer. Rice was cultivated in the field, while rye-grass was grown in a phytotron. Fertilization with (NH4)2SO4 caused a 16% increase in the yield of rice grains and urea a 36% increase. In both crops total N uptake and N use efficiency of the fertilizers were higher for urea than for (NH4)2SO4. The low values for N derived from fertilizer showed that the fertilizers contributed little to the total N absorbed by the plants. The "priming effect" or positive added N interaction (ANI) between the fertilizer N and soil organic N was observed, especially with urea. Immobilization by soil microorganisms was greater in the presence of urea, while losses were always higher with the (NH4)2SO4 treatments. These losses were significant, and their reduction should allow more efficient use of this N fertilizer. It is possible that the N use efficiency was higher for urea due to a pH increase, caused by urea hydrolysis, which in turn may have favoured the activity of nitrifying bacteria in this extremely acid soil.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 13 (1992), S. 1-5 
    ISSN: 1432-0789
    Keywords: Nitrification inhibitor ; Dicyandiamide ; 15N ; Incubation ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The influence of temperature on the action of a dicyandiamide nitrification inhibitor was studied during a laboratory incubation after the addition of ammonium sulphate labelled with 15N. In the control treatment, nitrification was only slightly affected by temperature and was rapid; on the 42nd day, two-thirds of the 15N was incorporated into the nitrate fraction while no further tracer was found in ammoniacal form. With the addition of dicyandiamide, the process was slowed down considerably when the temperature was maintained at 10°C, and only about 10% of the 15N was nitrified in 6 months. After 1 month of incubation at 10°C, a temperature increase to 15°C for 4 weeks modified the nitrification kinetics only slightly. However, as soon as the temperature reached 20°C, the beginning of dicyandiamide decomposition and an increase in the quantity of NO 3 - -N was observed. The inhibition was measured by the nitrification index, which was greater than 80% as long as the temperature did not exceed 15°C, and decreased to 10% after 6 months; this value was reached only after 1 year in soil maintained at 10°C. The half-life of the NH 4 + was decreased by raising the temperature. In the experimental conditions described, nitrification was inhibited by the dicyandiamide for at least 6 months provided the temperature did not exceed 15°C.
    Type of Medium: Electronic Resource
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