1. Soils & Plant Nutrition Rodney Pond PhD Student School of Environmental and Forest Sciences

2. Overview What are the essential plant nutrients & why? What are the sources essential nutrients? How do nutrients become available to plants? How do plants take up nutrients? What are the factors that limit nutrient availability for plants? How do you cultivate soil for optimal nutrients?

3. Essential Plant Nutrients 16 essential nutrients needed for plant growth CHOPKNS CaFe Mg B Mn CuZn MoCl (C. Hopkins Café – Managed by my cousin Michael) Macronutrients - needed in large quantities Primary nutrients- carbon, hydrogen, oxygen, nitrogen, phosphorus, and potassium Secondary nutrients-calcium, magnesium, and sulfur Micronutrients - needed in small quantities boron, copper, iron, chloride, manganese, molybdenum, and zinc

4. Roles of nutrients in plant growth Primary macronutrients Carbon – energy capture, energy storage & physical structure Hydrogen – same as above + osmotic potential Oxygen – same as carbon plus terminal electron acceptor Phosphorus – cell membranes, DNA/RNA, proteins, energy storage & trasnsfer Potassium (K) – enzyme activation, cellular transport, protein, sugar and hormone formation Nitrogen – Building block for amino acids and proteins, DNA/RNA

5. Roles of nutrients in plant growth Secondary macronutrients Calcium – Cell walls, regulation of nutrient uptake Magnesium - Chlorophyll Sulfur – Amino acids, proteins, enzymes, defensive chemicals

6. Roles of nutrients in plant growth Micronutrients Boron – Translocation of calcium, sugars & plant hormones, regulation of plant structures Manganese – Chlorophyll synthesis Copper – Enzyme co-factor in photosynthesis Zinc – Enzyme co-factor Iron – Chlorophyll synthesis & function Molybdenum – Enzyme co-factor in amino acid synthesis, nitrogen metabolism Chloride – Osmotic balance

7. Roles of nutrients in plant growth Also important to some plants Silicon – Strengthens cell walls Nickel – Nitrogen metabolism Sodium – replaces K in some plants Cobalt – Key to nitrogen fixation

8. Nutrient Sources Non-mineral nutrients- carbon, hydrogen, and oxygen Supplied by water and air Mineral nutrients – All the rest *Supplied by organic matter and weathering of rock What about nitrogen? Both mineral and non-mineral sources nitrogen fixation

9. Nutrient Acquisition Photosynthesis CO 2 + H 2 O = C 6 H 12 O 6 + O 2 Stomata Nitrogen fixation N 2 + 8H + + 8e - = 2NH 3 + H 2 Root nodules

10. Nutrient Acquisition Everything else? *Active transport through roots from the soil solution Plants can ONLY uptake mineralized nutrients

11. Nutrient Availability Chemical & physical weathering of rock AKA soil formation slow & in minute quantities Decomposition of organic matter AKA mineralization main source of nutrients

12. Nutrient Availability Nutrient cycling Movement of nutrients through organic to mineral forms through ecosystems Nutrients can be gained, stored, and lost

13. Nutrient Availability Gained – fixed into living matter Stored – in living and decomposing matter Lost – by transport, volatilization, and leaching Disturbed ecosystems in general have lost their ability to gain and/or store nutrients

14. Nutrient Availability Limitations to nutrient availability Primary production – formation of organic matter Decomposition rate – how fast mineralization happens Soil moisture Soil temperature Soil chemistry – pH & cation exchange capacity

15. Nutrient Availability Soil moisture & temperature primarily effect nutrient availability through decomposition rate Warmer & moister = faster decomposition BUT fast does not mean better Balancing storage & loss

16. Nutrient Availability Storage in soil Humus – a complex of multitudes of organic molecules that are the products of decomposition Clay – the smallest class of soil particles & the only chemically reactive one Colloids! Negatively charged therefore hold on to cations in the soil solution therefore anions easily lost via leaching Cation exchange capacity – very important soil characteristic!

17. Nutrient Availability Cations – H, K, Ca, Fe, Mg, Mn, Cu, and Zn Anions – OH-,P, S, N, B, Mo, and Cl Soil pH regulates availability of cations & anion in solution

18. Managing Soil for Nutrients All comes down to feeding & care of the soil biota What do soil organisms need? Air Water Food Habitat

19. Managing Soil for Nutrients Air Soil biota are largely aerobic heterotrophs – they need O 2 Plant roots need O 2 as well N 2 for nitrogen fixation *Therefore soil needs to be well aerated

20. Managing Soil for Nutrients Water Soil biota largely live in the soil solution i.e. they’re more or less aquatic organisms As OM decomposes and nutrients are mineralized water transports and stores nutrients *Therefore soil needs to retain moisture

21. Managing Soil for Nutrients Food The soil ecosystem runs on organic matter – dead organisms and the shed parts of live organisms The rate at which OM is decomposed is restricted by nitrogen availability – C:N Therefore there needs to be a consistent source of food

22. Managing Soil for Nutrients Habitat Organisms need space to live – less space means fewer organisms means lower decomposition rate Therefore soil must have an open structure – pores

23. Managing Soil for Nutrients A “healthy” soil has a porous structure that allows for the movement of water, air, and organisms. Any action that preserves and promotes a porous soil structure improves nutrient availability

24. Managing Soil for Nutrients Amendments Organic – compost & other forms Inorganic – chemical fertilizers, mined minerals Surface protection AKA mulch Organic – woodchips, straw, covercrops, etc. Inorganic – plastic sheets, weed blocker, etc.

25. Managing Soil for Nutrients Plant symbionts Mycorrhizae, nitrogen fixing bacteria More is not necessarily better when using soil additives! Assess and test your soil to know what it needs BEFORE adding anything

26. It’s got what plants crave