Is Urea a Slow-Release Form of N?
Because of the fact that urea must be converted to ammonium and nitrate nitrogen for its use by plants, some people describe urea as being a "slow-release" form of N. Field performance data show this is not the case. The conversion of urea-N to ammonium-N and on to nitrate-N is rapid, and under Kentucky's soil, climatic, and cropping conditions is not considered to represent a "slow release" of N either for application to fallow land ahead of the intended crop, for application at or after time of planting, or for application onto grass sods
u prevodu: urea se uopšte ne razlaže sporo.
Post je spojen: [time]1290540589[/time]
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High soil pH also stimulates volatilization losses as shown in Table 2. Ten percent of the N in urea left on the soil surface for 4 days may be lost through volatilization when the soil pH is 6.0. At pH 7.5, volatilization losses double to 20% when urea is left on the soil surface for 4 days
ureu treba što pre inkorporirati.
ako je ph zemljišta 6 za 4 dana 10-ak % može da "ode" u vazduh.
sa ph=7.5 gubici su 20-ak % za 4 dana.
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gubici će biti veći za ureu koja nije inkorporirana, ako je zemlja vlažna a temperatura veća od 15 stepeni.
Post je spojen: [time]1290566063[/time]
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evo jednog drastičnog primera.
ph=7
temperatura preko 24 stepena
10 dana urea stoji na površini i ne inkorporira se
gubici 40%
Post je spojen: [time]1290592046[/time]
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koga zanima, a zna engleski, više info na sledećoj adresi:
http://webcache.googleusercontent.c...cts/UREA46.pdf+"Soil+Conditions"+urea&ct=clnk
