Submitted to: Potash and Phosphate Institute Guides
Publication Type: Other
Publication Acceptance Date: 8/9/1999
Publication Date: N/A
Technical Abstract: Determining the amount of nitrogen (N) fertilizer to apply to meet crop needs is challenging since inorganic forms of N tend to be very transient in soils. Factors such as precipitation, soil temperature, and amounts and types of freshly added plant residues influence N availability from organic matter decomposition. In spite of the dynamics of N in agricultural soils, ,effective diagnostic tools and procedures have been developed that can hel farmers make good N management decisions. Some of these same tools are now being used to help develop variable-rate N management plans within fields. New technologies are also being developed and adopted. In general, two sources of within-field variability should be considered when determining which tools and procedures are most important for developing variable-rate N management zones: 1) the variability of the soil to supply N to the crop, typically determined with some type of soil testing (e.g., soil nitrate or soil organic matter); and 2) the variability of the soil to provide a suitable rooting environment for crop plants or the yield potential of the soil, typically determined by some type of soil/yield classification (e.g., soil maps, yield maps, soil electrical conductivity; drainage maps, soil water storage).