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Soils 102 – Chemical properties. Soils 102 – Chemical properties. It’s more than just salt. Outline. Introduction Topics: Nutrients pH salinity/sodicity Practical matters Summary. Introduction. Chemical elements. Nitrogen nitrate ammonium Phosphorous Potassium Calcium Magnesium
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Soils 102 – Chemical properties It’s more than just salt ...
Outline • Introduction • Topics: • Nutrients • pH • salinity/sodicity • Practical matters • Summary
Introduction • Chemical elements ...
Nitrogen nitrate ammonium Phosphorous Potassium Calcium Magnesium Aluminum Sodium Hydrogen N NO3- NH4+ P (PO43-) K (K+) Ca (Ca2+) Mg (Mg2+) Al (Al3+) Na (Na+) H (H+) Chemical elements
Introduction • Chemical elements ... • Where are the nutrients, salts, etc.?
- - - - - - - - Mineral particle (sand, silt, clay) - - - - - - - - - - - - - - - - -
K+ - - Ca2+ Al3+ - - Mg2+ K+ - - - - Mineral particle (sand, silt, clay) - - - - - Al3+ Ca2+ - - K+ Mg2+ - - Fe2+ K+ -
Mg2+ H+ H+ K+ Ca2+ Al3+ Na+ K+ Ca2+ Mg2+ H+ H+ K+ Ca2+ Al3+ Na+ K+ Ca2+ Mg2+ H+ Mg2+ H+ Ca2+ Na+ Ca2+ H+ K+ Al3+ K+ - - Ca2+ Al3+ - - Mg2+ K+ - - - - Mineral particle (sand, silt, clay) - - - - - Al3+ Ca2+ - - K+ Mg2+ - - Fe2+ K+ - - - - - - - - Adsorbed to particle surface
Mg2+ H+ Ca2+ Na+ Ca2+ H+ K+ Al3+ Mg2+ H+ H+ K+ Ca2+ Al3+ Na+ K+ Ca2+ Mg2+ H+ H+ K+ Ca2+ Al3+ Na+ K+ Ca2+ Mg2+ H+ Mg2+ H+ Ca2+ Na+ Ca2+ H+ K+ Al3+ K+ - - Ca2+ Al3+ - - Mg2+ K+ - - - - Mineral particle (sand, silt, clay) - - - - - Al3+ Ca2+ - - K+ Mg2+ - - Fe2+ K+ - Available in soil water Adsorbed to particle surface
Nutrients • How are nutrients held to the mineral soil?
Negative charges on particle surface Mg2+ H+ Ca2+ Na+ Ca2+ H+ K+ Al3+ Mg2+ H+ H+ K+ Ca2+ Al3+ Na+ K+ Ca2+ Mg2+ H+ H+ K+ Ca2+ Al3+ Na+ K+ Ca2+ Mg2+ H+ Mg2+ H+ Ca2+ Na+ Ca2+ H+ K+ Al3+ - - - - - - - - Mineral particle (sand, silt, clay) - - - - - - - - - - Available in soil water Adsorbed to particle surface
Nutrients • How are nutrients held to the mineral soil? • Organic matter – another source
Organic matter Mg2+ H+ Ca2+ Na+ Ca2+ PO4- K+ Al3+ Mg2+ H+ NO3- K+ Ca2+ Al3+ Na+ K+ Ca2+ Mg2+ H+ PO4- K+ Ca2+ Al3+ Na+ K+ Ca2+ NO3- H+ Mg2+ H+ Ca2+ Na+ Ca2+ PO4- K+ Al3+ - - - - - - - - - - - - - - - + + -
Mg2+ H+ Ca2+ Na+ Ca2+ PO4- K+ Al3+ Mg2+ H+ NO3- K+ Ca2+ Al3+ Na+ K+ Ca2+ Mg2+ H+ PO4- K+ Ca2+ Al3+ Na+ K+ Ca2+ NO3- H+ + Mg2+ H+ Ca2+ Na+ Ca2+ PO4- K+ Al3+ - - - - - - + + - - - - - - - - - - - - - + - - + + + - - -
Mg2+ H+ Ca2+ Na+ Ca2+ PO4- K+ Al3+ PO4- Mg2+ H+ NO3- K+ Ca2+ Al3+ Na+ K+ Ca2+ Mg2+ H+ PO4- K+ Ca2+ Al3+ Na+ K+ Ca2+ NO3- H+ Na+ + Ca2+ Mg2+ H+ Ca2+ Na+ Ca2+ PO4- K+ Al3+ - - - - H+ - - + K+ + - NO3- - - - - - - Mg2+ - K+ - NH4+ - - - NO3- - + - - + + + - NO3- - - NH4+
pH • A measure of acidity/alkalinity
pH • A measure of acidity/alkalinity 1 7 14 Acid Neutral Base
pH • A measure of acidity/alkalinity • Which nutrients are basic, acid? 1 7 14 Acid Neutral Base
pH • A measure of acidity/alkalinity • Which nutrients are basic, acid? • Basic – Ca2+, Mg2+, K+ , (Na+) • Acid – H+, Al3+, Sulfur 1 7 14 Acid Neutral Base
pH • A measure of acidity/alkalinity • Which nutrients are basic, acid? • Which of these predominate in the Plains? 1 7 14 Acid Neutral Base
pH • A measure of acidity/alkalinity • Which nutrients are basic, acid? • Which of these predominate in the Plains? • Average pH of ND soils? 1 7 14 Acid Neutral Base
Soil pH levels, upland positions, non-manured sites, 1998. (Franzen, 1999)
pH • A measure of acidity/alkalinity • Which nutrients are basic, acid? • Which of these predominate in the Plains? • Average pH of ND soils? • How pH affects nutrient availability 1 7 14 Acid Neutral Base
pH • A measure of acidity/alkalinity • Which nutrients are basic, acid? • Which of these predominate in the Plains? • Average pH of ND soils? • How pH affects nutrient availability • How pH affects tree survival and growth 1 7 14 Acid Neutral Base
pH and trees • Deciduous more tolerant of high pH than conifers are (Michigan jack pine example)
pH and trees • Deciduous more tolerant of high pH than conifers are (Michigan jack pine example) • Conifer needle litter reduces the soil pH over time
pH and trees • Deciduous more tolerant of high pH than conifers are (Michigan jack pine example) • Conifer needle litter reduces the soil pH over time • pH < 4 aluminum toxicity
pH and trees • Deciduous more tolerant of high pH than conifers are (Michigan jack pine) • Conifer needle litter reduces the soil pH over time • pH < 4 aluminum toxicity • Which conifers appropriate to high pH?
pH and trees • Deciduous more tolerant of high pH than conifers are (Michigan jack pine) • Conifer needle litter reduces the soil pH over time • pH < 4 aluminum toxicity • Which conifers appropriate to high pH? • Ponderosa pine • Rocky Mountain juniper • Eastern redcedar
Salinity • High soluble salt concentration
Salinity • High soluble salt concentration • Not necessarily high sodium salts
NaCl Na2SO4 NaHCO3 Na2CO3 MgCl2 MgSO4 CaCl2 Sodium chloride Sodium sulfate Sodium bicarbonate Sodium carbonate Magnesium chloride Magnesium sulfate Calcium chloride Soluble salts
How do saline soils (seeps) develop? • Salts already present (esp. W of Mo. Riv.)
How do saline soils (seeps) develop? • Salts already present (esp. W of Mo. Riv.) • Salts dissolve in water and move
How do saline soils (seeps) develop? • Salts already present (esp. W of Mo. Riv.) • Salts dissolve in water and move • Water evaporates, leaving concentrated salts
Salinity • High soluble salt concentration • Not necessarily high sodium salts • Measured by electrical conductivity (EC) • Units are mmhos or dS/m
Salinity • High soluble salt concentration • Not necessarily high sodium salts • Measured by electrical conductivity (EC) • Units are mmhos or dS/m • NDSU soils lab recommendations: • 0-1 Non-saline • 1-2 Very slightly saline • 2-4 Slightly saline • 4-6 Saline • >6 Strongly saline