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Soil Fertility

Soil Fertility. Montana Small Grain Guide pages 35-42. Essential Elements. Nutrients from Air and Water: Carbon, Hydrogen, Oxygen CHO Primary Nutrients: Nitrogen, Phosphorus, Potassium NPK Secondary Nutrients: Sulpher, Calcium, Magnesium SCaMg Micronutrients:

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Soil Fertility

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  1. Soil Fertility Montana Small Grain Guide pages 35-42

  2. 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

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

  4. 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

  7. 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

  8. 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

  9. Interpretation • Must consider: -crop nutrient requirements -expected yield -cropping history -tillage & residue mgmt techniques

  10. 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)

  11. 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

  12. 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

  13. 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

  14. 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

  15. Timing of Fertilizer Application • Small grains take up most of their Nitrogen early in the growing season • Nitrogen applied after tillering usually won’t affect yield

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