Soil Fertility

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Soil Fertility

• Montana Small Grain Guide
• pages 35-42

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Essential Elements

• Nutrients from Air and Water
• Carbon, Hydrogen, Oxygen CHO
• Primary Nutrients
• Nitrogen, Phosphorus, Potassium NPK
• Secondary Nutrients
• Sulpher, Calcium, Magnesium SCaMg
• Micronutrients
• zinc, iron, magnanese, copper, boron, molybdenum,
  chlorine

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Essential Nutrients

• C HOPKNS CaFe Mg B Mn CuZn ClMo
• See Hopkins Café Managed By Mine Cousin Clomo

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Soil Fertility

• Harvesting crops removes nutrients from the soil
• Chemical fertilizer, animal waste, sewage sludge

5
Nutrient Deficiencies

• Visual symptoms can give a clue to deficiencies
• Tissue analysis identify shortages
• At this time it is usually too late to correct

6
Soil Testing

• Availability of nutrients in soil
• Soil sample collection
• Lab analysis
• Interpretation of test results
• Recommendation

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Soil Sampling

• Collect at least 20 subsamples to 6 depth for
  standard soil tests
• Nitrogen test 6-12, 12-24, 24-48
• Avoid areas not representative of field
• Place subsamples in clean plastic bucket
• Mix samples, select approx. one cup in plastic bag

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Soil Sampling

• Mail with name, field ID, depth of test,
  information sheet
• Nitrate test samples must be dried or frozen
  immediately after collection
• prevent soil organisms from converting organic N
  to nitrate

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Interpretation

• Must consider
• -crop nutrient requirements
• -expected yield
• -cropping history
• -tillage residue mgmt techniques

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Nitrogen

• Wheat Barley take up Nitrogen in the ammonium
  (NH4) and nitrate (NO3)
• Most nitrogen in soil is tied up in the organic
  matter
• 1-3 becomes available to the crop each year by
  microorganisms
• Mineralization Organic matter breaks down to
  ammonium (NH4)

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Nitrogen

• Nitrification ammonium is converted to (NO3)
• Soil temps below 40 deg., nitrification is very
  slow
• Nitrate is very mobile, moves readily with water
  (Leaching)
• Ammonium is attracted to the clay minerals and
  organic matter

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Nitrogen Budget

• Determine realistic yield goal
• Determine crop Nitrogen requirement
• -yield goal x constant
• -wheat 2.5
• -barley 1.8
• Subtract soil test N from total N requirement

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Nitrogen Budget

• Add 20 for each ton of residue incorporated just
  before planting
• -1 bu. Yield 100 of straw
• Subtract 30 if alfalfa was previous crop
• Subtract 8 for each ton of manure
• Remainder is N fertilizer requirement

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Nitrogen Budget Example

• Goal is 30 bu/ac of Spring Wheat
• Tests show soil has 30/acre
• Previous crop yield was 20 bu/ac
• Add 10 tons of manure/ac
• How much N should be added?
• ((30 x 2.5)-30)20-80-15
• Do not need to add N

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Timing of Fertilizer Application

• Small grains take up most of their Nitrogen early
  in the growing season
• Nitrogen applied after tillering usually wont
  affect yield

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