Integrated Nutrient Management

Section R

SWES 316

What is Integrated NM?

¨ Considering more than just yield-limiting factors when managing nutrients.

¨ Simultaneous consideration of:– Factors affecting crop yield– Factors affecting crop quality– Economic factors– Environmental factors– “System” factors

The Goals of Nutrient Management are to…¨ Optimize plant production

– Yield/quality– Profit

¨ Conserve resources¨ Enhance soil quality and productivity

Why Integrated NM?

¨ One cannot manage nutrients in isolation from other factors. Nutrients must be managed as a part of a cropping system because:– Other factors controlling plant growth will

also affect nutrient demand and nutrient fate.

Crop-Related Factors

¨ Growth rate (phenology)

¨ Nutrient uptake rate¨ Salt tolerance¨ Heat tolerance¨ pH tolerance¨ Is the crop harvested,

all or part?¨ Water consumptive

use

¨ Unique nutrient needs¨ Root system depth and distribution¨ Tissue test levels throughout growing season¨ Yield potential¨ Yield¨ Soil temp requirement¨ Insect infestation

Soil-Related Factors¨ Chemical/Biological:

– EC (salt)– SAR (sodium)– CEC– Antecedent plant-

available nutrients– pH– OM content– CaCO3 content– Mineralizable N (SOM)– Disease history

¨ Physical:– Texture– Water-holding capacity– Structure/restrictive layers– Soil Depth

¨ Other– Soil management history– Soil variability

Weather-Related Factors

¨ Annual rainfall/relation to crop C.U.¨ Annual rainfall distribution¨ Climate:

– Average air/soil temperatures during the year– Heat unit accumulations

Irrigation Factors¨ Water pH¨ Water ECw

¨ Water SAR¨ Water SO4

2-, Cl-, HCO3-, CO3

2- , H3BO3, Na+, Ca2+, Mg2+

¨ Availability/cost of water¨ Crop leaching requirement¨ Irrigation system: type of system, capabilities wrt

amount of water, frequency, uniformity

Fertilizer Factors

¨ Equipment availability for fertilizer application¨ Irrigation system capabilities¨ Inorganic or organic fertilizer?¨ If organic, need the mineralization rate¨ Compatibility of fertilizers with soil/water¨ If CRF, need release rate¨ Fertilizer costs¨ Is the fertilizer solid, liquid, gas? Mobile or

immobile? Acid or alkaline?

Summary

¨ Based upon these lists, we have counted at least 75 different pieces of information that will be needed to make wise, informed decisions about nutrient management.

¨ Where does the information come from?– Grower Experience– Published scientific information– State Extension services (Land Grant Univ.)– Private sector - commercial enterprises

Crop Factors

Corn Phenology Source: Iowa State University

Corn K Uptake Source: Iowa State University

Broccoli N Uptake

A

B

0

1

2

3

4

5

6

0 50 100 150

Days After Planting

Dai

ly N

Flu

x (k

g ha

-1 d

ay-1)

1993-94

1995-96

0

50

100

150

200

250

300

350

0 50 100 150

Days After Planting

To

tal

N U

pta

ke

(kg

ha-1

)

1993-94

1995-96

20

40

60

80

100

0 2 4 6

Soil EC

% Y

ield Lettuce

Broccoli

Cantaloupe

Sweet Corn

EC and Crop Growth

“Non-saline” “Saline”

NO3-N in Broccoli Petiole Sap

0

200

400

600

800

1000

1200

1400

1600

4-6 Leaf 10-12 Leaf First Buds HeadDevelopment

Pre-Harvest

NO

3-N

in S

ap (m

g/L)

Excessive

Adequate

Warning

Deficient

Malting Barley - Response to N

R2 = 0.9943R2 = 0.8426

0

500

1000

1500

2000

2500

3000

3500

4000

0 50 100 150 200 250 300

N Applied (lb/ac)

Yie

ld (

lb/a

c) Crystal 1997

Crystal 1998Yield

Quality

Good Irrigation Management is EssentialSource: Paul Brown, UA

Soil Factors

Soil Test Guidelines for Cantaloupes

If preplant soil NO3-N is:

0-5 ppm add 50-75 lb N/acre6-10 ppm add 50 lb N/acre>10 ppm add 0-50 lb N/acre

If preplant soil P (HCO3 method) is:

<5 ppm add 40-100 lb P2O5/acre5-15 ppm add 0-40 lb P2O5/acre >15 ppm add 0 lb P2O5/acre

Variability of Salinity in Soil

In this case, saltmanagement, notnutrients, may bethe key to cropproductivity.

Soil Salinity August 2003

0 10 20 30 40 50 60

0-3 in

0-1 in

0-0.5 in

Soil

EC (d

S/m

) Furrow

40" Low F

80" Low F

40" High F

80" High F

Soil ECe(dS/m)

After germination irrigation

Irrigation/Water/Weather Factors

Leaching Requirement for Pecans

0

5

10

15

20

25

0 500 1000 1500

Irrigation Water Salinity (ppm)

Lea

chin

g R

equi

rem

ent

(%)

Timing and amountof leaching irrigationshould be consideredwhen managingfertilizer.

Ensure fertilizer compatibilitywith water, and with otherinjected chemicals in pressurized irrigation systems.

Compatibility will dependon water pH, HCO3

-, Ca2+,EC, etc.

Fertilizer Factors

Organic Fertilizers

Fertilizer Prices

Material $/ton $/#N$/#S

Gypsum 40 NA 0.11Sulfuric acid 80(soil) NA 0.12Sulfur 250 NA 0.14Nitro-Sul 250 0.63

0.31Thio-Sul 190 0.79

0.36N-Phuric 190 0.63

0.59UAN-32 185 0.29

NA

Example: Integrated Nutrient Management for Cotton in Arizona

Courtesy of J.C. Silvertooth

Key Tools for Managing N in Cotton

¨ Use split applications¨ Follow crop development/N needs

– % Fruit Retention (FR)– Height to Node Ratio (HNR)– Petiole NO3-N concentrations (PN)

¨ Remember importance of avoiding excess N because of negative influence on reproductive performance of the plant.

Generalized Flower Curve

Heat Units Accumulated After Planting

Nu

mb

er

of

Fresh

Blo

om

s

Pinhead Square Peak Bloom

Cut-out

Possible N Management Approaches

¨ Scheduled fertilization based upon either– stage of growth or calendar dates

¨ Feedback approach (recommended)– crop condition (HNR, FR, PN)– Interpretation of feedback depends on stage of

growth (HUAP)– reference to established baselines

Feedback Management Requirements

¨ Useable / accessible measurement¨ Established baselines / guidelines

– reference base¨ Common variety types (species)¨ Regionally specific baselines¨ Validation of recommendations

Optimal N Management

¨ Provides for optimal N efficiencies– agronomically (crop response)– economically– environmentally

¨ Improved fertilizer N efficiency– better fertilizer N recoveries

¨ Reduced leaching losses

Steps for Optimal N Management

1. Establish a realistic yield goal

2. Account for soil and irrigation water available N

3. Split N applications

4. Follow crop conditions throughout the growing season and adjust N application accordingly

Optimal N Management (Step 1)

¨ Use realistic yield goal– 60 lbs N/bale

• Unruh, B.L. and J.C. Silvertooth. 1996– Upland and Pima, Arizona

• Mullins, G.L. and C.H. Burmester. 1990.– Upland, Alabama

– sets upper limit for crop N needs• assumes high N fertilizer efficiency

Optimal N Management (Step 2)

¨ Account for residual soil NH4-N and NO3-N– Each 1 ppm NH4-N or NO3-N in the top 12

inches of soil equals about 4 lb N/ac of available N

¨ Account for irrigation water NO3- - N

• 2.7 X ppm NO3- -N = lbs N/acre ft water

¨ Subtract these values from total N needs

Optimal N Management (Step 3)

¨ Split N fertilizer applications– follow crop condition (HNR, FR, petiole

concentration)– window = PHS - PB (600 - 2000 HUAP)

¨ Avoid preseason N applications if possible

N Application Window

Heat Units Accumulated After Planting

Nu

mb

er

of

Fresh

Blo

om

sPinhead Square Peak Bloom

Cut-out

Split N Applications

Optimal N Management (Step 4)

¨ Monitor Crop Condition:– Fruit Retention (FR)

• Yield potential is generally related to fruit retention. Lower fruit retention, especially late in the season means lower yield potential.

– Height to Node Ratio (HNR)• HNR is related to vegetative/reproductive balance.

Higher-than-normal values mean excessively vegetative plants, so N application should be delayed.

– Petiole NO3-N• A direct measure of plant N status

Optimal N Management Example

¨ 3 bale yield goal X 60 lbs N/bale = 180 lbs N/acre (estimate of upper N fertilizer rate)

¨ Subtract residual soil and irrigation water N– Ex. 15 ppm NO3

- -N residual/top 12 in = 60 lbs N

¨ Subtract water NO3-N– Ex. 5 ppm NO3-N x 4 ac ft/ac = 54 lbs N

¨ 180 – 60 – 54 = 66 lbs N minimum¨ Add 20% to allow for inefficiency = 80 lbs N¨ Split in 3-4 applications (PHS-PB)

N Management Irrigated Cotton

¨ First application at PHS– approximately 50 lbs N/acre

¨ Irrigate/cultivate¨ Second application near FB

– evaluate crop condition (FR, HNR, petioles)¨ Irrigate/cultivate¨ Third application before PB

– evaluate crop condition (FR, HNR, petioles)

HNR Baselines

Heat Units Accumulated After Planting

500 1000 1500 2000 2500 3000 3500

Hei

gh

t (i

n.)

/No

de

Ra

tio

0.0

0.5

1.0

1.5

2.0

2.5

FR Baselines

Heat Units Accumulated After Planting

500 1000 1500 2000 2500 3000 3500

% F

ruit

Ret

enti

on

0

20

40

60

80

100

120

Petiole NO3--N Concentration

Baselines

Heat Units Accumulated After Planting

500 1000 1500 2000 2500 3000 3500

Pet

iole

NO

3- -N (

pp

m x

100

0)

0

5

10

15

20

25

30

Excess

Adequate

Deficient

Warning

Crop Monitoring - N Management

Heat Units Accumulated After Planting

500 1000 1500 2000 2500 3000 3500

% F

ruit

Ret

enti

on

0

20

40

60

80

100

120

[1]

[1][1]

[1][1]

[1]

[2]

[2][2]

[2][2]

[2]

[3][3]

[3][3]

[3][3]

Heat Units Accumulated After Planting

500 1000 1500 2000 2500 3000 3500

Hei

gh

t (i

n.)

/No

de

Ra

tio

0.0

0.5

1.0

1.5

2.0

2.5

[1]

[1]

[1] [1] [1] [1]

[2]

[2]

[2][2]

[2][2]

[3]

[3][3]

[3][3]

[3]

Crop Monitoring

¨ Case 1– High fruit load (high fruit retention)

• HNR within thresholds • N input needed• If decline in petiole NO3

--N is observed– provide application of N fertilizer

Heat Units Accumulated After Planting

500 1000 1500 2000 2500 3000 3500

% F

ruit

Ret

enti

on

0

20

40

60

80

100

120

[1]

[1][1]

[1][1]

[1]

[2]

[2]

[2]

[2][2]

[2]

[3]

[3][3]

[3][3]

[3]

Heat Units Accumulated After Planting

500 1000 1500 2000 2500 3000 3500

Hei

gh

t (i

n.)

/No

de

Ra

tio

0.0

0.5

1.0

1.5

2.0

2.5

[1]

[1]

[1] [1] [1] [1]

[2]

[2]

[2][2]

[2][2]

[3]

[3][3]

[3][3]

[3]

Crop Monitoring

¨ Case 2– Low fruit load (low fruit retention)

• HNR is high (relative to guidelines)– hold back or reduce N fertilizer inputs– consider Pix application

Heat Units Accumulated After Planting

500 1000 1500 2000 2500 3000 3500

% F

ruit

Ret

enti

on

0

20

40

60

80

100

120

[1]

[1][1]

[1][1]

[1]

[2]

[2]

[2]

[2][2]

[2]

[3]

[3][3]

[3][3]

[3]

Heat Units Accumulated After Planting

500 1000 1500 2000 2500 3000 3500

Hei

gh

t (i

n.)

/No

de

Ra

tio

0.0

0.5

1.0

1.5

2.0

2.5

[1]

[1]

[1] [1] [1] [1]

[2]

[2]

[2][2]

[2][2]

[3]

[3][3]

[3][3]

[3]

Crop Monitoring¨ Case 3

– HNR is low (relative to guidelines)• maintain N fertilizer inputs• Pix is not needed

– Crop is experiencing some form of stress• water, N, salinity, etc.

– limiting growth

– Identify and correct

Heat Units Accumulated After Planting

500 1000 1500 2000 2500 3000 3500

% F

ruit

Ret

enti

on

0

20

40

60

80

100

120

[1]

[1][1]

[1][1]

[1]

[2]

[2]

[2]

[2][2]

[2]

[3]

[3][3]

[3][3]

[3]

Heat Units Accumulated After Planting

500 1000 1500 2000 2500 3000 3500

Hei

gh

t (i

n.)

/No

de

Ra

tio

0.0

0.5

1.0

1.5

2.0

2.5

[1]

[1]

[1] [1] [1] [1]

[2]

[2]

[2][2]

[2][2]

[3]

[3][3]

[3][3]

[3]