Practical nutrient management
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What element helps grasses stand upright
Silicon
Nitrogen fixing plants need which nutrient?
Cobalt
Plant toxic nutrients
Aluminium and Mn in acid Na and Cl in saline B in saline too These can be toxic to animals that eat them too
How plant roots take up nutrients
Respiration provides energy for this
How can plants impact their soil environment?
How they take up nutrients affects resulting pH of soil since they release cations or anions to take up nutrients
Types of release mechanisms of nutrients
Dissolution Organic matter decay Cation exchange (fast)
Do you know the tank analogy?
Differences in active nutrients in tanks with large or small pools including if that is organic or CEC tied
Organic matter decay will happen the quickest in which environments?
Moist, warm, aerated soils Releases N, S, and P sometimes
Nutrients from cation exchange
Ca, Mg, and K (rapid process)
Weathering (Dissolution)
Most important in young soils, acid conditions
Specific adsorption/desorption
P, Mo, B, Cu, Zn Strong bonding processes on oxides and volcanic ash
Surface chelation/release
Fe, Cu, Zn, Mn (metals) Also toxic materials such as lead Strong bonding processes on humus Slow release rates
Transport in soil
Mass Flow - from soil water, solubility determines Diffusion - individual molecules through gradients, soil is moist and warm
How roots respond to different transport mechanisms
They have to branch out to nutrients who use diffusion by making a diffusion gradient through surface area. They put at the surface of soils because that’s where nutrients are added
Impediments to root growth
Physical: dry, structureless soils that are dense and have few macro pores Chemical: oxygen deficiency, Ca deficiency, Al excess, organic toxins Biological: disease organisms
What is availability?
Ability of soil to maintain high content ration in solution in vicinity to roots Determined by: 1) concentration 2) rate of release 3) mobility
Why are nutrient losses higher in fertile soils?
You have more nutrient density so if you have erosion you’ll lose more per volume than a poor soil
Types of Losses
Erosion - mostly P and N in solids Crop removal - N and K removed most , can minimize by returning back residues Gaseous - ammonia volatilization in alkaline soils, nitrate and sulfate reduction in wet environments, burning of N and S Leaching - loss of soluble nutrients through water, phosphate loss only in sandy soils, minimize loss by fertilizing at right time
Why do healthy plants use nutrients better
More biomass so harvesting more nutrients
Where does phosphorus fertilizer come from?
Rock phosphate, mostly apatite
Where does N fertilizer come from?
Ammonia is the base for most N fertilizers and can be created from Haber Bosch. It can be turned into anhydrous ammonia by putting through pressure and low temps
Where does potassium fertilizer come from?
Mined from sedimentary deposits of KCl and potassium sulfate
Where does sulfur fertilizer come from?
Gypsum - mined from sedimentary rocks, abundant, fairly soluble Elemental sulfur - mined, insoluble, oxidizes in soils Superphosphate - contains calcium sulfate
Determining fertilizer needs
Educated guess Interpretation of visual symptoms Soil samples Plant samples Nutrient response trials (too slow and expensive)