The impact of late applications of N-fertilizer on the grain protein of wheat in the Mediterranean

climatic region of Western Australia

Jairo A Palta

Bill Bowden

Senthold Asseng

Supported by

Introduction

1. The AWB has recently introduced payments for wheat grain protein in order to improve its marketability

Grain protein prices for Western Australia wheat in 2000-2001

150

175

200

225

250

275

300

4 6 8 10 12 14 16

Grain Protein content %

AUD/t

Introduction

2. These payments have made decisions on the application of fertilizer N to wheat more critical for profits.

N applications, early growth and grain protein content

3. Grain protein can be increased by pre-tillering applications of fertilizer-N through an improved early vegetative growth.

Pre-tillering N applications and grain protein content

N applied

(Kg/ha)

N at maturity

(g m-2)

Grain N

yield

(g m-2)

NHI

Grain protein

(%)

Grain yield

(t/ha)

 

15 5.2  3.5  0.68

  

10.2 

 

1.94

15/15 6.7 4.5 0.67 11.4 2.26

30/30 8.6 5.4 0.63 13.1 2.35

 l.s.d.

(P=0.05)

1.32 0.71 0.03 0.79 0.32

Leaching of N

4. Water loss by deep drainage can occur in early winter when vegetative growth and N uptake is slow.

Low recoveries of N-fertlizer

Leaching of N

Leaching of N and rainfall distribution

5. Leaching of N is mainly a consequence of the distribution of rainfall.

70% of the annual rainfall is received between May-July.

Mediterranean-type environmentWestern Australian wheat-belt

ETpot

sowing grain fill

Month of year

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Rainfall and ET pot

(mm/month)

0

50

100

150

200

250

300

Information on management of grain protein

6. Growers are seeking information that delay decisions and expenditure on N fertilizer until late in the season when weather, yield potential and grain prices are clearer.

Aim

Evaluate the efficacy of post-tillering applications of N-fertilizer in increasing the grain protein content in wheat.

Post-tillering N applications and grain protein content

Wongan Hills in the central wheatbelt of WA.

390 mm annual rainfall

Deep yellow earthy sand (USDA Typic Xeric Psamment).

Post-tillering N applications and grain protein content

Seeding N (kg/ha)

Post-tillering 15N-fertilizer

SE(DC25) B (DC42) A (DC61)

  0

     

30kg/ha    

  30kg/ha  

    30kg/ha

 50

     

30kg/ha    

  30kg/ha  

    30kg/ha

Grain yield (t/ha)

012345

Phenostage of N application (DC)

0 25 42 61

Grain protein

(%)

89

1011121314

0N 50N

0N50N

1997Seeding N:0 kgSeeding N: 50 kg

Grain yield (t/ha)

012345

0N 50N

1998

Phenostage of N application (DC)

0 25 42 61

Grain protein

(%)

89

1011121314 0N 50N

Seeding N: 0 kgSeeding N: 50 kg

Jun Jul Aug Sep Oct Nov

Monthly rainfall (mm)

01530456075

1997

0 25 42 61

Uptake efficiency

late N-fertilizer (%)

010203040506070 Seeding N:0 kg

Seeding N:50 kg

Phenostage of late N application (DC)

Jun Jul Aug Sep Oct Nov

Rainfall (mm)

01530456075

1998

Phenostage of late N application (DC)

0 25 42 61

Uptake efficiency

late N-fertilizer (%)

010203040506070 Seeding N: 0 kg

Seeding N: 50 kg

Conclusions

Post-tillering applications of N-fertilizer to wheat can increase grain yield and protein content in seasons when:

1. There are not losses of water and N from deep drainage.

2. Late rains are capable to keep the soil surface moist for long enough to allow the fertilizer-N to be taken up by the crop.