Plant Nutrition and Soils

1. Plant Nutrition and Soils Chapter 29

2. Plant Nutrition • Plant Nutrition- uptake from the environment of all raw materials required for essential biochemical processes. • More than 60 elements have been identified in plants. • 1880s- ten chemical elements were designated as essential for plant growth. • Carbon, hydrogen, oxygen, potassium, calcium, magnesium, nitrogen, phosphorus, sulfur, iron. • 1900s- manganese, zinc, copper, chlorine, boron, molybdenum, and finally nickel. 17 Essential Elements

3. Essential Elements Three criteria are used to judge essentiality • If it is needed for the plant to complete its life cycle. • If it is part of any molecule or constituent of the plant that is itself essential. • Magnesium in chlorophyll molecule. • Nitrogen in proteins. • If deficiency symptoms appear in the absence of the element.

4. 2 Types of Essential Elements • Macronutrients- required in large amounts. • 1000 mg/kg or > of dry matter. • Micronutrients (trace elements)- required in very small amounts. • 100 mg/kg of dry matter. Certain plants contain unusually high and low amounts of specific elements. Silicon

5. Macronutrient Functions • Sulfur- amino acids and coenzyme A. • Phosphorus- ATP, nucleic acids, phospholipids. • Magnesium- chlorophyll molecule. • Calcium- cell walls, cofactors, cellular membrane. • Potassium- osmosis and ionic balance, stomatal activity. • Nitrogen- amino acids, proteins, nucleotides, nucleic acids, chlorophylls. • Oxygen, Carbon, and Hydrogen- almost all chemical molecules, 96% of the plant.

6. Micronutrient Functions • Molybdenum- nitrogen fixation and nitrate reduction. • Nickel- enzyme functioning in nitrogen metabolism. • Copper- involved in some REDOX reactions. • Zinc- activator or component of many enzymes. • Manganese- enzyme activator, membrane integrity, oxygen release in PSN. • Boron- Ca2+ utilization, nucleic acid synthesis, membrane integrity. • Iron- chlorophyll synthesis. • Chlorine- osmosis and ionic balance.

11. Global Nitrogen and Phosphorus Use

12. Nitrogen Losses ~ 1500 lbs/day or $500/day!

13. Asynchrony Between N Supply and Demand Source: G. Philip Robertson IN Ecology in Agriculture, L.E. Jackson, ed.

14. NUISANCE ALGAE BLOOMS

15. Eutrophication – Lake Tahoe story Data courtesy of C.R. goldman and J.E. Reuter, Tahoe Reesrach Group, U. of California-Davis, http://www.news.ucdavis.edu/tahoetv/

16. Soil • Soil- primary nutrient (inorganic ions), water, suitable gaseous environment, and support medium for plants. • Provides a chemical and physical environment for plant growth. • Minerals- naturally occuring inorganic compounds that are usually composed of two or more elements. i.e.- Quartz (SiO2), Calcite (CaCO3).

17. Soil Layers (Horizons) • Soils consists of at least 3 horizons (layers) A Horizon= topsoil. B Horizon= subsoil. C Horizon= soil base. Bedrock= below the horizon.

18. Soils Are Composed of Solid Matter and Pore Space • Solid Matter- fragments of rock and minerals in the soil. Coarse Sand 200-2000 µm Fine Sand 20-200 µm Silt 2-20 µm Clay < 2 µm • Pore Space- the space around the soil particles. • Air • Water

19. Plant Pathology- bacteria

20. Plant Pathology- viruses

21. Plant Pathology- fungi