2015 GRDC Topdressing for Irrigators. Rob Norton - - PDF document

1

2015 GRDC Topdressing for Irrigators.

Finley, Monday August 10, 2015.

Rob Norton http://anz.ipni.net @ANZIPNI

4R Nutrient Stewardship

• The 4Rs are the foundation

and guiding principles of nutrient BMPs (Roberts 2007)

• Approach is simple … apply

the correct nutrient in the amount needed, timed, and placed to meet crop demand The 4R’s is both:

• a process (what needs to be

considered) and

• an outcome (how the pieces

fit together)

http://anz.ipni.net

Source Time Place Rate

• 1. Supply in plant available forms
• 2. Suit soil properties
• 3. Recognize synergisms among

elements

• 4. Blend compatibility
• 1. Appropriately assess soil

nutrient supply

• 2. Assess all available

indigenous nutrient sources

• 3. Assess plant demand
• 4. Predict fertilizer use efficiency
• 1. Assess timing of crop uptake
• 2. Assess dynamics of soil nutrient

supply

• 3. Recognize timing of weather

factors

• 4. Evaluate logistics of operations
• 1. Recognize root-soil dynamics
• 2. Manage spatial variability
• 3. Fit needs of tillage system
• 4. Limit potential off-field

transport

The ¡basic ¡scien+fic ¡principles ¡of ¡managing ¡crop ¡ nutrients ¡are ¡universal ¡ ¡

Source Time Place Rate

2

Right source, rate, time, and place

• science-based principles
• not static
• Interdependent & applied in

cropping systems

• The 4Rs provide flexibility to nutrient

management recognizing that FBMPs are site and crop specific depending on soils, climatic conditions, crop and cropping history, and management expertise, and can be applied in large-scale, extensive agriculture or small family farms.

• Ignorance ¡more ¡frequently ¡

begets ¡confidence ¡than ¡ does ¡knowledge. ¡

– Charles ¡Darwin ¡

The 4R Nitrogen Quiz 12 Questions to ponder:

• The 4 R’s of nutrient

stewardship mean?

• How do I know if the crop needs

more N?

• What is the urea equivalent of

1m3 of broiler litter?

• Which is the most important N

loss pathway?

• N fertilizers contribute to soil

acidification by what process?

• When is it too late to apply N
• How much N can a crop take up

through its leaves?

• How does canola N demand

differ from wheat?

• What else can go wrong #1
• What else can go wrong #2
• What else can go wrong #3
• What can we do something

about?

Source Time Place Rate

3

System changes & responses Source/Rate/Place combinations

• Right Place
• Maximum urea (kg N) rates
• Worst Case – Canola, Light Soil, Urea/MOP, low SBU
• Best Case – Cereals, heavy soil, Super/MAP, high SBU

Source Time

Place

Rate

20 ¡cm ¡ ¡ 30 ¡cm ¡ 125 ¡mm ¡Share ¡ 33 ¡ 22 ¡ Spear ¡Point ¡ 13 ¡ 8 ¡ Crop ¡ Soil ¡ SBU ¡% ¡ 8% ¡ 17% ¡ 25% ¡ 33% ¡ Cereal ¡ Light ¡ 15 ¡ 20 ¡ 25 ¡ 30 ¡ Medium ¡ 20 ¡ 30 ¡ 35 ¡ 40 ¡ Canola ¡ Light ¡ 0 ¡ 10 ¡ 15 ¡ 20 ¡ Medium ¡ 5 ¡ 15 ¡ 20 ¡ 30 ¡

http://seed-damage-calculator.herokuapp.com

4

N deficiency in wheat Read the crop….

N-rich strips?

Shoot numbers = no per square meter - tillers and main stems good measure of integrated N supply up until DC30 Target shoot numbers = rainfall+mm irrigation = 400+200 = 600/m2

• 0.8
• 0.6
• 0.4
• 0.2

0.2 0.4 0.6 0.8 1 1.2 200 400 600 800 1000

5

N content of typical fertilizers

• Types

– N as nitrate – N as ammonium – N as amide – N as organic

• Content to application

Application Rate (kg prod/ha)

= 100*kg N/%N eg Urea = 100*50/46 = 109

Name %N Kg product to supply 50 kg N Urea 46% 109 UAN 42% w/v 118 l AmSul 21% 238 Poultry Litter ~2.5% dwt 3 m3 Amm Nitr 34% 147 Pot Nitrate 13% 385 MAP 10% 500 Anhydrous 82% 61

Litter – age, density, moisture content

N losses – enhanced efficiency fertilizers

• Immobilization

– high C soils

• Leaching

– Light soils, wet.

• Denitrification

– High C, wet soils

• Volatilization

– Surface ammonium sources. Nitrification inhibitor Polymer coating Urease inhibitor

6

How Nitrogen affects soil acidity

• Nitrification - H+ is released during the

conversion of NH4

+ to NO3

• Leaching - NO3
• carries basic

ions with it. They are replaced by H+

• Ammonium fertilizers and acidity

NO3

• N Source

Lime Eq. (kg lime/ kg N) Kg Lime/ kg fertilizer AmS 6 1.15 MAP 6 0.67 DAP 4 0.63 Urea 2 0.92 Pot Nit

NH4

+

H

+

Intervention Options GRDC – N timing*form*rate 2013 Trial Locations

SFS – Jon Midwood, HRZ Regional Cropping Solutions Network.

0, 25, 50 kg/ha N DC32, DC39, DC55, DC70 UAN, GrUrea, SUrea. 8 sites across HRZ, report on 3 from Victoria

Effect of timing – mean of all sites, rate and source.

Time% % Yield% Protein% N%Rem% Weights% Screens% DC32% 5.54% 9.9% 97% 76% 7.8% DC39% 5.43% 9.9% 95% 75% 7.2% DC55% 5.33% 10.3% 97% 76% 7.2% DC70% 5.07% 9.8% 88% 75% 7.3% Sign% **% **% **% ns% ns% %

Early N = Yield – window is from DC32 to DC39 Late N = Protein – window s DC55 but before DC70

7

Foliar, soil or what??

• N is taken up through the leaves

– Urea > ammonium > nitrate

• Limited by either urea toxicity, salt burn or leaf area.
• Timing is important
• Worst effect if flag leaf is damaged
• Foliar uptake probably 10-15 kg N/

ha

• Rest is taken up through roots.
• Leaf and soil – amm. loss.

Removal?

• N ~ 25%+
• P ~ 10%+
• S ~ twice
• B ~ four fold
• Micros – more efficient that wheat

– N budget = 80 kg N/t reasonable for canola

!

! Canola! Wheat!

! Mean!seed! content! Removal!in!a!! 2.0!t/ha! @8%!MC! Mean!seed! content! Removal!in!a! 3.0!t/ha! @10%MC!

N! 4.28%! 79!kg! 2.33%! 62!kg! P! 5672!! 10.4!kg! 3329!! 9.0!kg! K! 6863!! 12.6!kg! 4606!! 12.4!kg! S! 4062!! 7.5!kg! 1742!! 4.7!kg! B! 12.0!! 22!g! 2.2!! 6!g! Cu! 2.9!!! 5!g! 4.8!! 13!g! Zn! 37.9!! 70!g! 23.0!! 62!g! Mn! 38.0!! 70!g! 43.5!! 117!g!

Source Time Place Rate

Canola and N – old variety. 4 waterings

38.0 39.0 40.0 41.0 42.0 43.0 44.0 45.0 46.0 47.0 48.0 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 0N 50N 100N 200N

Taylor et al. 1991, Kyabram Mean of 2 years data

Rainfed Yield Irrigated Yield Rainfed Oil Irrigated Oil

8

Timing?

• Early N

– Wheat 40 kg by GS30 – Canola 40 kg by SE

• Rapid N SE to FF

– Wheat and Canola – Ability to compensate

• Canola continues N uptake

– With added water – Terminated by temps >32oC

Source Time Place Rate

g/plant Change N supply Continue 55 DAS 90 DAS 7 3.1 68 49 210 69 14 60

Hocking 1987

0.5 1 1.5 2 2.5 3 3.5 4 4.5 100N 20/80N 50/50N Rainfed Irrigated

What don’t you know?

• Knowns & Should be Known

– What N is there & is it accessible

• Soil test / Soil guess (root depth).

– Rough yield estimate/target.

• Known Unknowns

– Plus - Soil mineralisation in-crop. – Minus - Losses of soil & applied N. – How much supplied ends up in the grain. – Improved yield estimate as season unfolds.

• Unknowns

– Frost, bugs, late heat. – Operation successful – but the patient died

9

So who do you call?

http://www.extensionaus.com.au/category/field-crop-nutrition

Also ask through twitter #AuCropNutrition

10

Understanding crop nutrition

• You get nothing for nothing
• Identify the limiting factor
• There are no silver bullets.

Some take aways

• There is no one N solution – 4R’s approach
• Invest in N between DC31 and DC55 as yield is king
• Late N to change grades is an option but luck is needed.
• Canola is different to wheat – yield response later.
• There would need to be compelling circumstances to

justify moving away from top-dressed urea, provided as the season unfolds.

• There is still a risk due to season.