Fundamentals of Soil Nutrient Dynamics

Steven Perakis

N2

P, S, Ca, Mg, K, Mo, Fe, ……

NN--Rich Soils Grow NRich Soils Grow N--Rich PlantsRich Plants

0.8

1.0

1.2

1.4

1.6

1.8

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Soil % N (0 – 10 cm)

Dou

glas

-Fir

Fo

liar

N (%

)

r2 = 0.71p < 0.001

Perakis et al. 2006

Nutritional Issues at NitrogenNutritional Issues at Nitrogen--Rich SitesRich Sites

• Phosphorus

• Sulfur

• Calcium, Magnesium, Potassium (base cations)

• Aluminum toxicity

• Micro-nutrients (Fe, Bo, Mn, Cu, Zn…)

• No deficiency

Weathering

Losses

Deposition & N-fixation

Phosphorus (P)

Phosphorus (P)

• Source: Apatite

• PO43- (H2PO4

- in forest soils)

• Chemically sticky (especially in Andic soils)

→ Iron (Fe3+), Aluminum (Al3+) – insoluble!

• Cycles readily through organic matter

Nitrogen Accumulation

Geological time

Tota

l Soi

l Nut

rient

s

Nitrogen

Phosphorus Depletion

Geological time

Tota

l Soi

l Nut

rient

s

Walker and Syers 1976

Nitrogen Phosphorus

Phosphorus Forms in Soils

Geological time

Tota

l Soi

l P

Sequence of P forms

occluded

organic

soluble

Primarymineral

Walker and Syers 1976

Sulfur (S)

Sulfur (S)

• Source: Pyrite and Gypsum, Seawater

• SO42-

• Somewhat chemically sticky

→ Iron, Aluminum, Calcium – soluble!

• Cycles readily through organic matter

Sulfur Inputs compared to Tree UptakeSulfur Inputs compared to Tree Uptake

Sources: NADP, Weathers et al. 1988, Binkley et al. 1992

WholeTree

Sulfu

r Fl

ux(k

g ha

-1yr

-1)

Precip& Fog

0

1

2

3

4

5

6

7

8

9

Bole &Branch

Bole Only

S° + 1½O2 + H2O → SO42- + 2H+

Fungicides, sulfur, and soils

Calcium (Ca), Magnesium (Mg)Potassium (K)

Base Cations - Ca, Mg, K

• Source: Many minerals, Seawater

• Ca2+, Mg2+, K+

• Very loosely held in soils

→ Ion exchange on organic matter and clays

• Very soluble and subject to leaching in acid soils

Base Cations in Soils

Soil Particle

Mg2+

Na+

Ca2+

Al3+

K+

H+

Cation exchange capacity

= sum of negative charges

Base saturation

% occupied by Ca+Mg+K+Na

Displacement series

H(Al3+)>H+>Ca2+>Mg2+>>K+=NH4

+>Na+

Base Cation Leaching

Soil Particle

NH4+ + 2O2 →

H2O + + Mg2+

Na+

Ca2+

Al3+

K+

H+

NO3- 2H+

Al3+

H+

0

100

200

300

400

500

600

0 10 20 30 40 50 60 70 80

NO3- (µeq l-1)

Non

-sea

-sal

t cat

ions

(µeq

l-1)

Calcium (Ca2+)

Magnesium (Mg2+)

Sodium (Na+)

Potassium (K+)

Compton et al. 2003

Coupled Nitrate & Base Coupled Nitrate & Base CationCation LeachingLeaching

Soil % N (0-10cm)

Soil

Ca

& M

g(m

eq/1

00g)

Soil

0

2

4

6

8

10

0 0.4 0.8 1.2

Foliar Calcium trackssoil Calcium

Folia

r Ca

& M

g(%

)

0

0.2

0.4

0.6 Foliage

Perakis et al. 2006

High soil N drives low soil calcium & magnesium

Mg, Ca, K Requirements for Tree GrowthMg, Ca, K Requirements for Tree Growth

Sources: NADP, Weathers et al. 1988, Binkley et al. 1992

6

0

2

4

Precip. InputsBole Uptake

Nut

rien

t Flu

x(k

g ha

-1yr

-1)

Magnesium Calcium Potassium

Strontium as a tracer for Base Strontium as a tracer for Base CationsCations

• Sr immediately below Ca on periodic table

• Similar chemical and biological behavior to Calcium

• Natural 87Sr/86Sr variations reflect different sources (e.g. atmospheric inputs vs. bedrock weathering)

Exchangeable(0.7094)

Strontium isotopes trace Base Strontium isotopes trace Base CationCation sourcessources

0

10

20

30

40

50

60

700.705 0.710 0.715 0.720 0.725

Soil

Dep

th (c

m)

Seawater (0.7092) Weathering (0.7217)

Wood(0.7093)

87Sr / 86SrPerakis et al. 2006

Base Cation Deficiencies in Forests:Base Cation Deficiencies in Forests:

• Red spruce in north and southeastern USA

• Sugar maple in eastern USA and Canada

• Mixed northern hardwood forests in eastern USA

• Loblolly Pine in southern USA

• Norway spruce in Europe

• Coastal Oregon Douglas-fir ???

WrapWrap--up: Nutrition in Nup: Nutrition in N--Rich SitesRich Sites

• Phosphorus - sticky, long-term depletion, organic matter

• Sulfur - abundant in precipitation, somewhat sticky

• Calcium - sparse in precipitation, readily leached

• Aluminum toxicity - ???, can disguise Ca deficiency

• Micro-nutrients - ???

• No deficiency - ???

Remillard 1999

Surface soil nitrogen tracks wholeSurface soil nitrogen tracks whole--soil Nsoil N

P-deficient

N-deficientP-sufficient

Foliar N:P ratios diagnose limitationsFoliar N:P ratios diagnose limitations

0

2

4

6

8

10

12

14

Folia

r N:P

(mas

s)

Elevation (m)

0 200 400 600 800

Nitrogen Cycle Dominates Forest Nutrition

Soil Organic Matter (SOM)

Plants

MicrobesNH4 NO3

Mineralization

Leaching to groundwater and

streams

NO, N2O NO, N2O, N2

N2

N2

DON

Immobilization

Foliar N:P ratios in coastal DouglasFoliar N:P ratios in coastal Douglas--FirFir

r2 = 0.45p = 0.001

0

2

4

6

8

10

12

14

0 200 400 600 800

Elevation (m)

Folia

r N:P

(mas

s)

N-limited

P-limited

Foliar N:P ratios in coastal DouglasFoliar N:P ratios in coastal Douglas--FirFir

r2 = 0.45p = 0.001

0

2

4

6

8

10

12

14

0 200 400 600 800

Elevation (m)

Folia

r N:P

(mas

s)

Elements > 0.1 % of plant dry mass are called macronutrients< 0.1 % are micronutrients

Element Principal function

carbon, hydrogen, oxygen component of all organic molecules

nitrogen (N) component of amino acids, proteins, chorophyll, nucleic acids

phosphorus (P) component of ATP, NADP, nucleic acids, phopholipids

potassium (K) ion/ osmotic balance, pH regulation, regulation of guard cell turgor

calcium (Ca) cell wall strengthening and functioning, ionic balance, membranepermeability

magnesium (Mg) component of chlorophyll, enzyme activiation

sulfur (S) component of amino acids, proteins

Much interest in SulfurMuch interest in Sulfur

Strand, Youngberg, Turner, Gessel, Edmonds …

Blake et al. 1988 – field experiment with N + S addition

”Because the field study does not provide a direct test of the N with S response …”

S was added with P, Ca, K Study stands responded to N alone – they were N deficientFertilization increased growth of low S stands

… decreased growth of high S stands