soil nutrients

what essential nutrients do plants need

17 total

• macronutrients: c, h, o, n, p, k, ca, mg, s

• micronutrients: b, cl, mn, fe, zn, cu, mo, ni, si, na

why is P naturally limiting in ecosystems

long geological cycle; extremely slow movement from ocean to land to soil

example policy related to N

4R nutrient stewardship - right source, rate, time, place

how do plants obtain nutrients from the soil

absorb dissolved ions + water through roots

what determines how well soils supply nutrients

soil quality (texture, organic matter, structure), climate, water availability

what happens when soil nutrients are deficient

stunted/slow growth, chlorosis; severe deficiency causes tissue death

why is soil a key nutrient reservoir

stores nutrients in minerals, OM, and exchangeable ions on clay/humus surfaces

what are the main “leaky” losses in the nitrogen cycle

• leaching: nitrate moves with water into groundwater

• runoff: n carried to surface waters

• volatilization: nh3 gas lost to atmosphere

• denitrification: no3- → n2- and n2 gas in waterlogged soils

why is no3- especially prone to leaching

it is negatively charged and does not bind to soil particles

what fertilizer decision is influenced by N leakage

timing, rate, placement, inhibitors - applied to reduce no3- losses

what is the main “leak” in the P cycle

runoff + erosion of P rich soil particles into water bodies

why doesn’t P leach like nitrogen

P binds strongly to soil minerals, especially in clays and Fe/Al oxides

why is P availability naturally low

most P is locked in primary minerals; slow weathering; long geological cycling

how can nitrification inhibitors reduce N leakage

slow nh4+ → no3- conversion, reducing leaching and n2o emissions

how does controlled drainage help

limits nutrient rich water from leaving fields

why use localized/banded P placement

reduces runoff risk and increases uptake efficiency

what practices reduce P erosion

conservation tillage, riparian buffers, wetlands

why is n2o environmentally significant

greenhouse gas 265x stronger than co2; lasts > 100 yrs; depletes ozone

how does excess N or P affect water

eutrophication → algal blooms → hypoxia → reduced water quality

how do N and P affect society

• limits fisheries and recreation

• affects drinking water safety

• causes ecosystem degradation

why are N and P economically important

essential for global food production; fertilizers boost yields and profitability

why can’t plants use atmospheric N2

triple bond requires large energy to break; only microbes and lightning can fix it

biological nitrogen fixation produces what form of N

ammonia (nh3→ nh4+ in soil)