TILLAGE INTENSITY, CROP ROTATION, and FERTILIZER

TECHNOLOGY for SUSTAINABLE WHEAT PRODUCTION … NORTH

AMERICAN EXPERIENCE7th International Wheat Conference

November 29, 2005Mar del Plata, Argentina

T.L. Roberts and A.M. JohnstonPotash & Phosphate Institute

Introduction

North America is a world leader in no-till crop production

Extent of no-tillage adoption worldwide, million hectares,

2004/05. USA 25.3Brazil 23.6Argentina 16.0Canada 13.4Australia 9.0Paraguay 1.7Indo-Gangetic-Plains1.9Bolivia 0.6South Africa 0.3

Spain 0.3Venezuela 0.3Uruguay 0.3France 0.2Chile 0.1Colombia 0.1China 0.1Others (estimate)1.5Total 94.6

Source: J. Hassell, Conservation Technology Information Center, personal communication

Introduction

North America leads the world in no-till crop production

USA produces about 60 billion t wheat and exports 30 billion t

Canada produces 26 billion t and exports 18 billion t

Northern Great Plains

Total area about 125 M ha52 M ha in crop production

Wheat is the dominant crop, followed by barley and oatsCorn is dominant only in the southern regions

Northern Great PlainsNorthern Great Plains

Canola is the dominant oilseed, grown mainly on the Canadian prairies

Dry peas and lentils … crop diversification option, but represent small proportion of cropping mix

Northern Great PlainsEnvironmental Conditions

Severe … cold winters and hot summers Moisture is limiting

300 to 500 mm of annual precipitation; 165 to 300 during the April to July growing season

Frost free period … 83 to 157 days Soils are frozen for 4 to 6 months …

minimizing microbial activity, nutrient release, and crop residue decomposition

No-till Wheat Production

Farmers in Canadian prairies and Northern Great Plains pioneered wheat production in reduced tillage systems.

No-till, or direct-seeding, is used on about ~third of U.S. wheat farms and half the Canadian wheat area.

No-till Wheat Production

Erosion control is the main reason for adopting no-till in much of the world, but in Canadian prairies … improved moisture efficiency

Soil zones of the Canadian prairies.

About 30 M ha of cultivated landSpring wheat is the principal crop

Rotations … historically included high proportions wheat and summerfallow, but fallow has been declining and no-till area is increasing

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

No

-til

l ar

ea,

M h

a

No-till area in the Canadian prairies.

Source: B. McClinton, Saskatchewan Soil Conservation Association

Trends in cropping intensity in the Canadian prairies.

Average rotation length*

Soil zone 1976 1980 1985 1990 1995 1998

Brown 1/1.1 1/1.1 1/1.3 1/1.3 1/1.3 1/1.6

Dark Brown 1/1.4 1/1.5 1/2.1 1/2.2 1/3 1/4

Black and Gray1/2.2 1/2.6 1/4.9 1/4.9 1/6.7 1/10*Interpret rotation 1/1.1 as one year fallow to 1.1 year in crop

Source: Campbell et al., 2002

Cropping Systems

Growers now incorporate cereals, oilseeds, pulse crops, and forages into their rotations.

Wheat still dominates, but the improved water conservation gives growers greater flexibility.

Soil Changes Related to Tillage

Tillage accelerates the natural processes of soil degradation Erosion, salinization, and

acidification increase amount and quality of

organic matter decreases

Reduced tillage … greater crop residues accumulate on the soil surface

When residues accumulate …

Less wind and water erosion … improved soil quality

Increased water infiltration and less evaporation

Cooler soil temperatures … slower nutrient release, reduced diffusion, less root growth

Changes in nutrient cycling … increases in N immobilization … eventually increased N mineralization

Immobile nutrients tend to accumulate at the soil’s surface

Soil pH may decline Fertilizer management becomes more

important

When residues accumulate …

0 5 10 15 20 25 30 35 40 45

300

400

500

600

700

800

900

1000

1100

1200

1300

Depth, cm.

Po

tass

ium

, m

g/k

g

Silty Clay Soil

Conventional Till

Zero Till

0 5 10 15 20 25 30 35 40 45

0

10

20

30

40

50

60

70

Conventional Till

Zero Till

Depth, cm.

Ph

osp

ho

rus,

mg

/kg

Silty Clay Soil

Effect of zero and conventional tillage on P and K distribution in a

Manitoba silty clay

Source: Grant and Bailey, 1994

Fertilizer Management

Fertilizer management in no-till seeding requires careful management to optimize nutrient use efficiencySoil characteristics, climate, crop type, and

agronomic practices impact nutrient use efficiency

Fertilizer Management

N is the most yield limiting nutrient world wide, followed by P and K

Broadcasting N onto surface covered residue is not efficient

Fertilizer Management

In-soil band placement of N is usually the most effective … reduces immobilization, but applying all the crop’s N requirements can be challenging

P and K applied in bands minimizes fixation and increases early season uptake … especially when applied as a starter

-400

-200

0

200

400

600

800

1000

1200

1967 1972 1977 1982 1987 1992 1997 2002

Yie

ld in

cre

ase

, kg

/ha

Wheat on Stubble Wheat on Fallow

Fallow = 342 kg/haStubble = 197 kg/ha

Mean

Yield increase from starter P in a Saskatchewan fallow-wheat-wheat rotation,

1967-2004

Source: R.P. Zentner, Agriculture and Agri-Food Canada

Influence of starter P on soil test P in the wheat phase of a Saskatchewan

fallow-wheat-wheat rotation, 1967-2004

0

10

20

30

40

50

60

1965 1975 1985 1995 2005

F-W-W (N+P) F-W-W (N)

Source: R.P. Zentner, Agriculture and Agri-Food Canada

Ols

en P

, kg/

ha

Fertilizer Management

All P needs for wheat can be safely applied at seeding … not so for N and K

Too much N and K can reduce germination and delay emergence resulting in poor stands and lower yields

Fertilizer Management

Many factors influence how much fertilizer can be safely applied with the seed

Row spacingSeed bed

utilization (SBU)Soil textureSoil moisture

Soil variabilityFertilizer placementSeed furrow openerFertilizer sourcecrop

Row Spacing

The amount of fertilizer that can be safely applied with the seed decreases as row spacing increases

30 cm20 cm10 cm

Row spacing ranging from 10 to 30 cm … higher concentrations of P in wider rows had no effect on yield (SK and MB research)

Seed Bed Utilization

Measure of the amount of soil used for applying fertilizer.

Calculated as:

%SBU = Width of seedrow

row spacingX 100

Seed Bed Utilization

Assuming a 2.5 cm seed row (knife opener) and a 10 cm row spacing

30 cm20 cm10 cm

25% 12% 8%

SBU = 2.5/10 x 100 = 25%

Seed Bed Utilization

Heavier textured soils tolerate more N because the increased cation exchange and water holding capacity reduces ammonia toxicity … a major cause of germination and seedling damage

Approximate Safe Rates of Urea-N (kg/ha) that can be applied with

wheat.2.5 cm spread

(Disc or knife) Row spacing, cm

15 23 30SBU, %

17 11 8Light 22 17 17Medium 34 28 22Heavy 39 24 24

Source: Henry et al., 1995

Approximate Safe Rates of Urea-N (kg/ha) that can be applied with

wheat.2.5 cm spread 7.5 cm spread

(Disc or knife) (Sweep) Row spacing, cm Row spacing, cm

15 23 30 15 23 30SBU, % SBU, %

17 11 8 50 33 25Light 22 17 17 45 34 28Medium 34 28 22 56 45 39Heavy 39 24 24 67 56 45

Source: Henry et al., 1995

Specialized Seeding Equipment

Many growers have adopted the use of specialty seeding equipment that places fertilizer in a separate band from the seed

No-Till Seeding Original Equipment

No-Till Seeding Present Equipment

Side Band Openers – Many to Choose From

Stealthtm Opener

2.5 cm

2.5 cm

3.8 x 7.2 cm 3.8 x 3.8 cm

Urea and anhydrous ammonia (NH3) are the two main N sources used by the region’s

farmers

NH3 is common in higher moisture regions, where higher N rates are required to optimize yields

0

50

100

150

200

250

0 56 84 112

Nitrogen rate, kg/ha

See

dlin

g st

and,

pla

nts/

m2

UreaAmmonia

AB and SK Locations

Wheat Seedling Response to Side Banded N Form x N Rate

0

500

1000

1500

2000

2500

3000

0 56 82 112

Nitrogen rate, kg/ha

Gra

in y

ield

, kg

/ha

UreaAmmonia

AB and SK Locations

Wheat Yield Response to Side Banded N Form x N Rate

Horizontal, Not Vertical Separation of NH3 Band is Critical to Avoiding Damage

Sulfur is the third most limiting nutrient in the Northern Great

Plains Estimated 30% of the

acreage in Canadian prairies is S deficient

SO4-S soil test is difficult due to variability of SO4 in the field and release of organic S S deficient wheat

S Fertilizer

S is normally applied as elemental S or as as SO4

Elemental S requires microbial oxidationTemperature, moisture, aeration, pH and particle

size influence oxidation Application of elemental S in the spring or

near planting is not recommended for annual crops because oxidation is too slowMixtures of bentonite and elemental S are

available which increase the dispersion of S particles and increase oxidation rates

Average wheat yield response to applied S in Alberta soils with no

previous S application

-S +S* Yield No. of --- kg/ha --- inc., % trials

Gr. Wooded soils 1422 1619 14 12Breton‡ 949 1830 93 20U of A§ 2482 2731 10 8

Source: Doyle and Cowell, 1993

* 15 kg S/ha as Na2SO4 ‡ Average total S=100 mg/kg, § Average total S=670 mg/kg

Average wheat yield response to applied S in Alberta soils with 20-year history of S

application-S +S Yield No. of

--- kg/ha --- inc., % trials

Breton‡ 1 774 1178 52 52 2059 2225 8 53 1690 2737 62 54 2523 3641 44 4

U of A§ 1 3379 3659 8 42 1999 2023 1 4

Source: Doyle and Cowell, 1993

* 15 kg S/ha as Na2SO4 ‡ Average total S=100 mg/kg, § Average total S=670 mg/kg

Effect of N, P, and S fertilization on wheat yields in Alberta.

Treatment N P2O5 S Yield Yield Inc.

------------- kg/ha ------------- %

1 0 0 0 2310 --2 0 0 22 2550 103 18 22 0 2480 74 18 22 22 3020 31

Source: Doyle and Cowell, 1993

Influence of N and P on wheat grown on fallow and stubble in a Dark Brown soil in

southern Alberta. Rotation sequence, 13-yr Ave. yield, kg/haFertilizer, kg/ha Fallow wheat Stubble wheat N P F-W F-W-W F-W-W Cont. W 0 0 2775 2332 1203 1156 0 20 2802 2641 1176 128445 0 2722 2460 1519 150545 20 3031 2654 1908 1747

Letters in bold face represent the phase of the rotation the yield was determined. Source: Campbell et al., 1990

Concluding Comments

Understanding soil nutrient behavior and its implications to fertility management is important to maximize nutrient use efficiency and wheat production in no-till

Soil testing is the best available tool to estimate soil nutrient levels and make appropriate fertilizer recommendations

Thank You