Soil and Mineral Nutrition

How is soil made?

mechanical weathering (rain, heat, cold, frost), spontaneous weathering, chemical weathering (acids, moisture)

Makeup of soil

25% Air, 25% Water, 45% Mineral particles, 5% Organic matter (humus, roots, organisms)

Studies performed to understand what is essential for plant growth

Measuring growth depending on concentration of nutrients given to plant (tomato and copper experiment)

Primary macronutrients of plants

nitrogen, phosphorous, potassium

Basic nutrients

carbon, hydrogen, oxygen

secondary macronutrients

calcium, magnesium, Sulphur

Chlorosis

yellowish, brittle, papery (lack of iron, manganese, zinc)

Nitrogen and phosphorus deficiency

purple, yellow leaves

Necrosis

premature death (potassium= leaf tips and margins), (manganese= leaf tissues and between veins)

Cation exchange

negatively charged soil particles hold onto essential positively charged nutrient ions (cations), then release them to plant roots to absorb by exchanging them with hydrogen ions

Why is too much acidity (lots of H+) bad for cation exchange?

H+ ions can clog soil exchange sites, leading to a higher chance of nutrients being leached away by water, because they are not automatically being exchanged.

Adaptations for pH

root modifications, symbiotic relationships, physiological responses

Nitrogen fixation

conversion of atmospheric gas (N2) into usable forms such as ammonia for living organisms, primarily performed by microbes, lightning

Nitrogen assimilation

overall process of organisms converting atmos. nitrogen into organic molcules

Nitrifying bacteria

convert harmful ammonia into nitrite, then nitrate, a form of nitrogen plants can use

Denitrification

nitrate is converted back to nitrogen gas (N2), removing it from plant and atmosphere

Carnivorous plants

lack of nitrogen in soil = gain nitrogen from digesting insects or small animals

Mineral storage

storage in vacuoles of cells (parenchyma)

Nitrogen reduction

nitrate converting into ammonia