Soil Chemistry Dr. Shalamar Armstrong sdarmst@ilstu.edu Dr. Rob Rhykerd rrhyker@ilstu.edu
Importance of soil Feeding the world
World Population & Growth Other Asia Africa India China Latin America Europe North America Source : UN Population Division, September 2007
How much more food will need to be produced? Current population: 7 billion 2050: 9.5 billion
Factors influencing food production More people (35% increase) Aging population will eat more Poverty moving to middle class Increase demand for meat Grain to produce Poultry Pork Beef
Food production by 2050 Will need to double!!! How will this occur? Let s look at available land
How much soil is there for growing crops? Apple example
Cutting away. Water covers 75% of Earth. 50% of that is desert, polar, or mountainous regions 40% is limited by terrain, fertility or excessive rainfall. How much is available????
Only 7.5 %!
How much water is available for people and food production?
If one gallon represents all the water on Earth Only ½ cup is fresh water Only one drop is available for humans and food production
Production must Increase on existing (and shrinking) soil resources using all technology available in an environmentally sustainable manner
What is Soil?
Presentation Title (View > Master > Slide Master) Components of Soil Idea Growing Conditions for a Loam Soil 2-Porous Component Air Water 1-Solid Component Mineral Organic Material Department/Unit/Office/Organization (View > Master > Slide Master)
Soil Colloids Size Presentation Title (View > Master > Slide Master) Soil Particle Sand Silt Size 2mm 0.05mm 0.05mm - 0.002mm Clay 0.002mm - 2µm Colloid <2µm The diameter of a clay particle on average is 2000 times larger than a soil colloid. Department/Unit/Office/Organization (View > Master > Slide Master)
Clay Question: Does the soil have charge?
Cation Exchange Capacity Active Soil Solution Ca +2 K + Al +3 Ca +2 Ca +2 Ca +2 +2 Ca +2 Mg +2 H + K + H + Mg +2 Mg +2 Ca +2 Exchangeable Cations Ca +2 K + - - Ca - +2 S - O Mg - +2 I - K L + H + - - Al +3 - - - Reserve Active Soil Solution Al +3 Ca +2 Mg +2 H +
Plant Root-Soil Solution-Colloid Ion Exchange Root hair surface H + Mg 2+ K + Ca 2+ K + Ca 2+ K+ H+ OM Mg 2+ K + NH 4 + Ca 2+ NH 4 + H+ NH 4 + K+ H + Clay Colloid Mg 2+ Mg 2+ Ca 2+ K+ Soil Air Ca 2+ Clay Colloid K + H+ Soil Solutio
Pools of Acidity H Al K NH 4 H NH 4 H H - - - - - - - - - - - - - - - - H Ca H H Na Mg Al K Reserve/Exchangeable Acidity- H + on the exchange complex H H H H H H Active- H + in solution
Presentation Title (View > Master > Slide Master) Key Concepts The properties of water Capillary Rise vs. Soil Pores Soil Water Potential/Energy Saturated Flow / Unsaturated flow Department/Unit/Office/Organization (View > Master > Slide Master)
Presentation Title (View > Master > Slide Master) Properties of Water Structure: asymmetrical, V- shaped at 105 Water exhibits polarity Electropositive near Hydrogen Electronegative near the Oxygen Attracted to and hydrates cations (H +, Ca 2+ ect.) Hydrogen Bonding H O H Department/Unit/Office/Organization (View > Master > Slide Master)
Presentation Title (View > Master > Slide Master) Properties of Water Cohesion-water molecule attracted to another water molecule Adhesion/adsorptionwater molecule attracted a solid surface. Department/Unit/Office/Organization (View > Master > Slide Master)
Water Movement in Soils Capillary Flow - Water moves up hill (or in any direction) due to the forces of adhesion and cohesion H (cm) =0.15 cm 2 radius The rise height of the liquid is inversely proportional to the size of the pore space Sandy loamclay loam Smaller pores produce greater adhesive forces
Capillary Rise and Soil Texture
A E Granular Platy B Blocky C Massive
Demonstration of Capillary rise Polarity Water solubility
Materials and Methods 1. 2. 3. 4. 5. Add ~ ½ inch of water