Lesson 4: Plant Nutrition and Defense
Soil
Highly weathered outer layer of the Earth’s crust
o
Mixture of sand, rocks, clay, slit, humus, mineral, and organic matter
The Earth’s crust includes an estimated 92 naturally occurring elements
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Most are found in the form of inorganic compounds called
minerals
Plants Depend on Soil
Topsoil
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the most organic rich
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Worms and other creatures love this layer
Subsoil
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Nutrients that have washed off from rocks
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Less organic
Bedrock
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Water moves laterally
Water and Mineral Availability
About half of the soil volume is occupied by pores
o
May be filled with air or water or both
Hydrogen bonds adhere water to soil particles and dissolve nutrients
Soil needs the right balance of sand, silt and clay
Soil composition can determine the relative proportions of air and water in soil spaces
Soils with high sand drain quickly
Soils with silt do not drain well therefore have little air
Most plants like a mix
Macro and Microelements
Most basic
nutrients are
elements
LEARN
Macro elements:
plant
nutrients required in
relatively large amounts
Microelements
: plant
nutrients required in
relatively small amounts
Chlorine= Cl=Closed
Manganese=Mn=Monday
Molybdenum=Mo=Morning
Copper=Cu=See u
Zinc=Zn=Zoon
Macronutrients
Micronutrients
Extracting Nutrients from the Soil
Minerals must be in solution
Important examples:
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Nitrate: NO
3-
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Potassium: K
+
Anions dissolve in soil water and are readily available to plants for uptake by roots
Loss of nutrients by water is called leaching and can have a harmful effect on soil fertility
