soils & plant nutrition rodney pond phd student school of environmental and forest sciences
TRANSCRIPT
Soils & Plant Nutrition
Rodney PondPhD Student
School of Environmental and Forest Sciences
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?
Essential Plant Nutrients16 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
Roles of nutrients in plant growth
Primary macronutrients
Carbon – energy capture, energy storage & physical structureHydrogen – same as above + osmotic potentialOxygen – same as carbon plus terminal electron acceptorPhosphorus – cell membranes, DNA/RNA, proteins, energy
storage & trasnsferPotassium (K) – enzyme activation, cellular transport, protein,
sugar and hormone formationNitrogen – Building block for amino acids and proteins,
DNA/RNA
Roles of nutrients in plant growth
Secondary macronutrients
Calcium – Cell walls, regulation of nutrient uptake
Magnesium - ChlorophyllSulfur – Amino acids, proteins, enzymes,
defensive chemicals
Roles of nutrients in plant growth
Micronutrients
Boron – Translocation of calcium, sugars & plant hormones, regulation of plant structures
Manganese – Chlorophyll synthesisCopper – Enzyme co-factor in photosynthesisZinc – Enzyme co-factorIron – Chlorophyll synthesis & functionMolybdenum – Enzyme co-factor in amino acid synthesis,
nitrogen metabolismChloride – Osmotic balance
Roles of nutrients in plant growth
Also important to some plants
Silicon – Strengthens cell wallsNickel – Nitrogen metabolismSodium – replaces K in some plantsCobalt – Key to nitrogen fixation
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 sourcesnitrogen fixation
Nutrient Acquisition
PhotosynthesisCO2 + H2O = C6H12O6 + O2
Stomata
Nitrogen fixationN2 + 8H+ + 8e- = 2NH3 + H2
Root nodules
Nutrient Acquisition
Everything else?
*Active transport through roots from the soil solution
Plants can ONLY uptake mineralized nutrients
Nutrient Availability
Chemical & physicalweathering of rock AKA soil formation
• slow & in minute quantities
Decomposition of organic matter AKAmineralization
• main source of nutrients
Nutrient Availability
Nutrient cycling
Movement of nutrients through organic to mineral forms through ecosystems
Nutrients can be gained, stored, and lost
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
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
Nutrient Availability
Soil moisture & temperature primarily effect nutrient availability through decomposition
rateWarmer & moister = faster decomposition
BUT fast does not mean better
Balancing storage & loss
Nutrient AvailabilityStorage 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!
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
Managing Soil for Nutrients
All comes down to feeding & care of the soil biota
What do soil organisms need?
AirWaterFood
Habitat
Managing Soil for Nutrients
AirSoil biota are largely aerobic heterotrophs – they
need O2
Plant roots need O2 as well
N2 for nitrogen fixation
*Therefore soil needs to be well aerated
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
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
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
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
Managing Soil for Nutrients
Amendments
Organic – compost & other formsInorganic – chemical fertilizers, mined minerals
Surface protection AKA mulch
Organic – woodchips, straw, covercrops, etc.Inorganic – plastic sheets, weed blocker, etc.
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
It’s got what plants crave