Ecology of nutrients

Cycles

Flows

Stocks

Key terms

The ecology of nutrients

Internal cycling

Nutrient inputs

Nutrient losses

• Chemical weathering of rocks

• Biological fixation of atmospheric N

• Deposition of elements from atmosphere

• Transfer of nutrients

Between plants and soil

Between organic and inorganic forms

• Changes in ionic forms

• Biological uptake

• Interactions with mineral surfaces

• Leaching

• Gaseous emissions

• Wind and water erosion

• Fire

• Harvest

Ecosystem

Internal cycling is most important in natural ecosystems

Source of plant nutrient (% of total)

Nutrient Deposition/fixation Weathering Recycling Nitrogen 7 0 93 Phosphorus 1 < 10 > 89 Potassium 2 10 88 Calcium 4 31 65 Data from (Whittaker et al. 1979)

Nutrient budget for Hubbard Brook Forest

100%1%0.1%0.01% 10%0.001%

Elemental concentrations in soil vs. earth’s crust

soil

crust

Adapted from Essington (2003)

Which forms of nutrients are bioavailable?

ions in

solution

exchangeable

ions

“active” OM

humus

weatherable

minerals

All participate in biogeochemical cycles

but rates of “flow” vary widely.

Nutrient ecology in agroecosystems

What’s

missing?

Dissipation into the surrounding

environment via erosion, leaching,

volatilization…

How big should this arrow be?

Unfortunately

environmental losses are

sometimes larger than

nutrient removal in harvest

SOM - N

4000 160 80

200 200

Microbial

Biomass N

NO3- + NH4

+

From the

atmosphere

50

To the

atmosphere

10-50 FertilizerCrop

uptake

Loss by

leaching

20-100

N budget for Rothamsted wheat experiment

The total N stocks in soil normally greatly

exceed annual flows

#s = kg/ha (0.89*kg/ha = lbs/ac)

Jenkinson

Mineralized soil N

wheat pasture

Potential

N uptake by

Without fertilization, N is often a limiting nutrient (i.e., N mineralization is often much slower

than potential crop uptake)

Peak uptake

~ 3 lbs of N/ac/day

"The most effective management

strategy will be one that recognizes the

pattern of nitrogen demand by the

crop and the nitrogen release

characteristics of all important

nitrogen sources to provide

adequate, but not excessive

levels of soil nitrogen

throughout the growing

season."

(Doerge, 1991)

Peak uptake = 5-10 lbs

of N/ac/day

(Dinnes et al., 2001)

Timing of availability has a big impact on uptake vs. losses

elementlow

(mg/kg)high

(mg/kg)average (mg/kg) lbs/ac- pl*

B 11 92 45 90

Cu 65 140 24 48

Mn 100 3907 480 960

Mo 0.4 6.9 2 4

Zn 20 770 65 130

Total stocks in prairie soil A horizons

* assumes 1 acre- plow layer = 2 million lbs w/ average conc.

Weathering, deposition and recycling often supply

trace elements at rates which are not limiting

elementTotal

lbs/ ac-pl

lbs removed by 150 bu

corn yrs

lbs removed by 60 busoybeans yrs

lbs removed by 6 ton alfalfa yrs

B 90 0.16 563 0.1 900 0.3 300

Cu 48 0.1 480 0.1 480 0.06 800

Mn 960 0.3 3200 0.6 1600 0.6 1600

Mo 4 0.008 500 0.01 400 0.02 200

Zn 130 0.27 481 0.2 650 0.24 542

Acre-plow layer stocks of trace elements expressed as years of removal by corn, soybeans and alfalfa

Dust leaving

the Sahara

“As soils develop in humid environments,

rock-derived elements are gradually lost,

and under constant conditions it seems that

ecosystems should reach a state of profound

and irreversible nutrient depletion. We show

here that inputs of elements from the

atmosphere can sustain the productivity of

Hawaiian rainforests on highly weathered

soils. Cations are supplied in marine

aerosols and phosphorus is deposited in

dust from central Asia, which is over

6,000km away.” ( Chadwick et al, 1999)mg dust/m2/yr

Average annual deposition of

Saharan dust in the Amazon basin

exceeds 10 million tons or

> 150 lbs/ac

Swap et al. (1992) concluded that

the productivity of the Amazon rain

forest is dependent upon trace

elements contained in dust

originating in the Sahara.

Total Ammonia Emissions by County (1995)

Where is all this ammonia coming from ??

50 lbs N/acre

Deposition of biological available N

1990s

N inputs to IL soils

Mg = 1 x 106 g = 1000 kg = 1 metric ton

1 metric ton = 2204.6 pounds

1 metric ton = 1.1023 US tons

(alfalfa and other forage legumes)

M.David

N outputs from IL soils

M.David

Crop specific harvests of N

M.David

Net N inputs Net input = Gross inputs - outputs

19

93

M.David

Mining Prairie N

Anthropogenic N inputs

M.David

Units are 1000 metric tons N / yr

-523,000 tons of N/yr !

M.David

Units are 1000 metric tons N / yr

+1 ton of N/yr !

M.David

Why does so much N get into Illinois’ rivers ???

Approximately 40% of IL fields

have artificial drainage

Yield maps have

made drainage

problems

more obvious

↓ more artificial

drainage

↓more nutrient

pollution

Photo: MARGARET BOURKE-WHITE

Aerial view of Cargill grain

elevator w. barges lined up on the

bank of the Chicago River in 1951

So where do the nutrients

in IL grain end up?

Redistribution of nutrients in the Mid-Atlantic region

excess

Counties with

large excesses

have the most

livestock

Surplus P and N

State P N

--Million of lbs in excess--

DE 7.3 14.6

MD 10.4 19.6

NJ 0.9 1.8

NY 3.3 4.2

PA 23.7 33.8

VA 24.8 42.3

(Source: USDA, 2001)

Why don’t we

send the

surplus

nutrients

back?

Keith Bowers of Multiform

Harvest in Seattle has

developed a system to

remove phosphates from

swine and dairy manure. It

involves changing the

chemistry of the liquid manure

to form struvite, a phosphate

compound that is precipitated

out of the slurry. Struvite,

magnesium ammonium

phosphate, is sometimes

deposited naturally as scale

on wastewater pipes and in

the human body as kidney

stones. It’s in demand as a

slow release fertilizer and

magnesium source.

http://www.fao.org/docrep/006/y5066e/y5066e02.jpg

Nutrient depletion in Africa

Nutrient budgets on organic farms

http://www.organic.aber.ac.uk/library/Nutrient%20budgets%20on%20organic%20farms.pdf

N

P

K

a review of published data

Most organic farms in developed countries do not

have nutrient deficits even though they don’t use

conventional fertilizers.

http://edis.ifas.ufl.edu/DS096

Daily inputs and outputs of dry matter, P and N

urine feces

N

P

K

50% 50%

10% 90%

90% 10%

N

20% maintenanceP

13% maintenance

K

12% maintenance

60%

20%

60%

27%

75%

13%

http://extension.oregonstate.edu/catalog/html/em/em8586/

http://edis.ifas.ufl.edu/DS096

Nitrogen budget for a dairy in Florida (lbs of N/acre)

Manure constituent Lbs/year/100 cows Probable $ value

Raw manure (feces + urine) 5,045,000

Water in fresh manure 4,458,990

Total solids 586,000

Total N (lb) 23,400 $3,5101

Total P (lb) 4,800 $2,8801

Total K (lb) 15,100 $2,2651

TOTAL VALUE of N, P, and K $8,655

1 Based on assumed values of $.30/lb N, $.60/lb P, and $.15/lb K; N recovered was 50%

of excretion, thus, 50% volatilized.

Annual manure production and nutrient value for a 100 cow dairy

There are ~ 500 “large" CAFOs and ~ 2,700 "Medium" CAFOs in IL.

These CAFOs are required to:

Apply for a National Pollutant Discharge Elimination System (NPDES)

Permit

Submit an Annual Report

Develop and implement a manure and wastewater handling plan

(Nutrient Management Plan).

Concentrated Animal Feeding Operations (CAFOs) in IL

In Illinois, there are actually 3 different types of manure management plans

that livestock facilities may be required to have (NRCS, IL DOA, and IL EPA).

U of I Extension has worked with NRCS, IL DOA, IL EPA to develop one

workbook of forms and instructions that when completed by a producer, will

comply with the requirements of all 3 agencies.

Nutrient

Balance

Problem

Overview of Hislop farm

1500 sow farrow-to-wean operation

32,000 piglets (with an average weight of 10 lbs) are sold off the farm each.

1500 acres of crops - 750 acres of corn - 50 % sold off the farm, 750 acres of soybeans – 100%

sold off the farm.

~ 1300 tons of feed purchased each year.

Manure from the sow operation is applied exclusively to corn ground. Fertilizer is also

applied to corn ground.

Nutrient inputs

Purchased feedPurchased fertilizerBiological N fixation

Nutrient inputs

How many tons of N, P and K are in 1300 tons of purchased feed ?

N 2% of 1300 tons = ? of N

P 0.8% of 1300 tons = ? tons of P

K 0.4% of 1300 tons = ? tons of K

Feed analysis?

Nutrient inputs

How many tons of N, P and K are in the purchased fertilizer ?

N 750 acres*100 lbs/acre*1 ton/2000 lbs = ? tons N

P 750 acres*25 lbs/acre*1 ton/2000 lbs = ? tons P

K 750 acres*50 lbs/acre*1 ton/2000 lbs = ? tons K

Fertilizer program? Acres? Fertilizer receipts?

Nutrient inputs

Biological N fixation

~ 3 lbs of N fixation per bushel of beans

750 acres of soybeans*50 bu/acre*3 lbs of N fixation/bu

Total nutrient inputs

∑Feed

Fertilizer

Biological N fixation

Nutrient outputs

Marketed grainMarketed piglets

Environmental losses∑

Nutrient cycling on-farm

Nutrients in manureNutrients in crop residues

Nutrients in 50% of corn grain

You are welcome to analyze

your family’s farm or any

other farm with which you

are affiliated.