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ISSUE 3  MAY 20, 1999

NITROGEN LOSS FROM SOILS

    Adequate and timely application of nitrogen fertilizer is critical for increasing sugarbeet yield and
sucrose content.

    Sugarbeet growers generally use anhydrous ammonia or urea as their primary nitrogen fertilizer to
provide ammonium and nitrate ions for the sugarbeet crop. However, some of the nitrogen applied is
lost from the soil. Movement of fertilizer in the soil are mainly by water-caused soil erosion and leaching.
Soil erosion will result in the loss of ammonium-nitrogen which is adsorbed to soil particles. Leaching will
result in the loss of nitrate-nitrogen which is highly mobile in soil and moves freely with soil water.

    Fertilizer nitrogen may also be lost by surface runoff, denitrification, and volatilization. Fertilizer nitrogen
that is broadcasted on soil covered with snow or ice could be lost in surface runoff. In waterlogged soil,
soil nitrates can be lost by denitrification whereby bacteria rapidly change soil nitrogen to unavailable
atmospheric nitrogen. Ammonium-nitrogen applied to the surface of alkaline (pH above 7) or calcareous
soils, especially under conditions of high soil temperatures and rapid evaporation, may cause the loss of
nitrogen as ammonia gas by the process of volatilization. Nitrogen applied as urea to the soil surface
converts rapidly to ammonia when adequate moisture, temperature, and the enzyme urease are present.
This ammonia can also be lost to the atmosphere through volatilization.

    Some practices that will minimize nitrogen loss from soil include incorporating fertilizer applied to
alkaline or calcareous soils, incorporating urea, proper placement of anhydrous ammonia in moist soil,
avoiding fall broadcast of nitrogen fertilizer where ponding may occur in the spring, and waiting until soil
temperatures are 50EF or lower before applying nitrogen fertilizer in the fall.

Mohamed Khan
Extension Sugarbeet Specialist
mkhan@ndsuext.nodak.edu


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