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Using soil texture to guide variable-rate nitrogen fertilization

Hobson, Jared and Ellsworth, Jason and Leytem, April and Pool, Ann (2004) Using soil texture to guide variable-rate nitrogen fertilization. pp. 35-41. In: Ellsworth, J.W. (ed.) Proc. Idaho Nutrient Management Conference. USA-ID-Twin Falls, 2004/03/11.

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Variable-rate fertilization is becoming a common practice in the US. Many
producers are applying phosphorus and potassium at site-specific rates that take into
account local factors that affect nutrient availability, crop growth and yield potential.
Phosphorus and potassium are relatively immobile in the soil and soil testing can be
effectively used to map the plant available concentration in the soil. Fertilizer spread
maps are created from interpolations of these samples. Nitrogen, however, is very mobile
in the soil. Sampling is only meaningful until the next rain or irrigation. Nitrogen is
highly affected by soil moisture and rainfall. It is more difficult to create fertilizer spread
maps based on soil N test values.
Nitrogen availability for crop growth is related to many soil factors. These factors
include organic matter, soil texture, topography, aspect, residues and previous crop. Of
these, soil texture has a large effect on N availability because it effects water holding
capacity. Nitrogen movement in the soil is highly related to water movement. Coarse
textured soils have higher infiltration rates and lower water holding capacity. Fine
textured soils have lower infiltration rates but high water holding capacity. The
combination of irrigation management and soil texture greatly affects the N availability to
a crop. In a site-specific management study by Machado et al. (2002), it was pointed out
that although the spatial variability of crop yields depends on the interaction between
many physical and biological factors, the effects of soil physical properties on crop yield
is predictable and therefore useful in variable rate technology.
Nitrogen is an important factor in the growth of most crops, especially in sugar
beets where it directly affects yield, sugar content and quality. With many crops the cost
of applying too much nitrogen is the cost of the excess fertilizer and application as well
as the environmental impact that is not a direct cost to the grower. However, applying
too much nitrogen to sugar beets will reduce sugar content and quality, which is a direct
cost to the grower. (Humburg and Stange, 1999).
This paper will present the results of a variable rate N study and the importance of
texture in determining the N rate and yield and yield quality.

Item Type: Conference or Workshop Item (Paper)
NWISRL Publication Number: 1134
Subjects: Soil > Chemistry > Nitrogen
Mass Import - autoclassified (may be erroneous)
Depositing User: Users 5 not found.
Date Deposited: 20 Nov 2010 21:56
Last Modified: 03 Nov 2016 16:14
Item ID: 928