Fertilizers and Grazing Wheat

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Fertilizers and Grazing Wheat

• Clay Robinson, Ph.D.
• Associate Professor, Soils
• West Texas AM University
• crobinson_at_mail.wtamu.edu
• 806/651-2553
• www.wtamu.edu/crobinson/DrDirt.htm

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Fertilizer Recommendations

• Nitrogen recommendations generally made based on
  yield goals
• Other nutrients usually added based on soil test
  results and yield goals

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Nutrient Removal

• Corn, grain - 0.8 lbs N/bu
• Corn, silage - 7.1 lbs N/ton
• Wheat - 1.2 lbs N/bu
• Wheat forage 25 lbs N/ton
• 4.5 lbs P/ton, 15 lbs K/ton
• Sorghum, grain - 1.0 lb N/bu
• Sorghum, silage - 14.8 lbs N/ton
• Cotton - 15.2 lbs N/bale (lintseed)

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Fertilizer Grades

• All fertilizers report the grade using three
  numbers, e.g., 28-3-3
• The first number is always nitrogen content, so
  28
• The second is phosphate, P2O5
• The third is potash, K2O
• The fourth, if present, is sulfur

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Fertilizer Grades

• P and P2O5 are not the same P 44 of the
  fertilizer grade
• K and K20 are not the same K 83 of the grade

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Fertilizer Application

• Put 50 to 70 of nitrogen by soil test down
  before season begins
• Apply rest in split applications through pivot or
  prior to canopy closure

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Flexibility

• If soil tests reveal adequate nitrogen, or
  climate conditions change the yield goal, less
  nitrogen can be applied, improving nitrogen use
  efficiency

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Flexibility

• Fate of winter wheat used for stockers can be
  decided in early February by considering soil
  moisture levels and fertility plan

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N Fertilizer Options for Grazing

• Graze-out
• Light grazing N fertilizer equivalent to 30
  bu/ac grain
• Moderate to heavy grazing N equivalent to 40
  bu/ac grain
• Recommendations based on soil test for
  nitrate-nitrogen

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P Fertilizer Options for Grazing

• Graze-out
• Light grazing P fertilizer equivalent to 70
  bu/ac grain
• Moderate to heavy grazing P equivalent to 90
  bu/ac grain
• None required if soil test P gt 45 ppm

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K Fertilizer Options for Grazing

• Graze-out
• Light grazing P fertilizer equivalent to 70
  bu/ac grain
• Moderate to heavy grazing P equivalent to 90
  bu/ac grain
• None required if soil test K gt 120 ppm (most
  soils in region)

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Fertilizer Options for Grazing

• Grain without grazing requires
• About 60 less N and P
• Same amount of K

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Nitrogen requirement (lb/ac) with Spring Soil
Nitrogen (Total N as NH4 NO3) tests in Winter
Wheat