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 4.0  BMPs for Nitrogen Fertilizer Management
 
Introduction
Nitrogen (N) is an essential plant element that frequently limits irrigated crop production in the Uncompahgre Valley. Commercial fertilizer and manure can be cost effective means of supplementing  N in the soil and are necessary for sustaining high crop yields. However, improper or excess use of N fertilizer can lead to nitrate pollution of ground and/or surface water. Fertilizer applicators can minimize the problem by implementing the following N fertilization management BMPs.

Guidance Principle
Manage N applications to maximize crop growth and economic return while protecting water quality.

BMPs for Nitrogen Fertilization

    4.1     A yearly N management plan should be developed for each field and crop. At a minimum, the plan should take into consideration: 
  • The previous crop, variety and yield.
  • The current crop, variety and expected yield.
  • Current soil test analysis data showing the amount of available N in the soil.
  • The amount of N available from soil or organic matter, manures, and from previous tilled legume crops that will become available during the crop growth period.
  • The amount of supplemental N to be applied to meet expected crop yield. This includes  N from chemical fertilizers, manures, irrigation water and other sources.
  • Management practices needed to reduce N leaching, including: timing of application, multiple applications, side dressing, banding, foliar feeding, fertigation, or needed changes in crops or crop rotation.
    4.2     Base N fertilizer rates on soil analyses and/or tissue sampling.
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FIGURE 6
General estimations of potential soil nitrogen losses occurring when nitrogen fertilizer is applied in a single (A) or in split applications (B).
 Source: Nitrogen Fertilizer Management in Arizona
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