SFS00025 - Evaluation of Late Nitrogen Applications to Achieve Yield Potential and increased protein content in wheat

Final Report

Project Start Date
15 August 2013
Project End Date
30 April 2014
Supervisor Name
Jon Midwood
Organisation
Southern Farming Systems
Contact name
Jon Midwood
Contact phone
0400 666 433
Region
South
Summary

This project aimed to contribute to the knowledge gaps identified by the high rainfall zone (HRZ) Regional Cropping Solutions Networks (RCSN) in the program logic for the very high priority issue of nitrogen (N) management.

The research question is:

Can we achieve optimum yield (measured at 11% protein) and still increase grain protein (to 12%) of wheat produced in the HRZ?

The specific question addressed is:

What impact will delaying the timing of N applications after growth stage 32 have on wheat yield and protein and is there an advantage of using solid or liquid fertiliser?

Trial sites were established in existing wheat crops to evaluate the impact of late (post-GS32) N applied at different application rates, products and timings on yields and grain quality.

Conclusions

When looking across all treatments, there were yield responses at three of eight sites, and protein responses at five of eight sites. This does not necessarily mean there were no N responses because some of the sites had individual treatments significantly different to the control. The mean response overall was 0.29t/ha and a protein increase of 0.5%. For the majority of sites, the key timing that influenced yield was GS39. There were no differences between product type and rate had a small effect. The higher rate of 50kgN/ha had a higher yield than 25kgN/ha. This timing is slightly later than previously thought suitable for applying N for yield, with GS32 being the recognised standard. The data needs to be interpreted with the 2013 season in mind because a tighter finish in spring could mean plant uptake of late applied N would be limited.

The most significant outcome from these trials was the very strong effect of increasing grain protein. In nearly all cases, the higher rate of 50kgN/ha had a more significant effect, as did delaying the timing until GS55. Interestingly, product type had very little effect on increasing grain protein, but this may have been influenced more by the softer finish to the season that most sites experienced. The late application at GS70 was just too late to impact on grain protein, even with a liquid fertiliser. This practice is widely used in Europe to increase grain protein, but that may suit a longer grain-filling period than we experience in Australia.

Guidelines for growers

1) Grain protein as an indicator of N management:

Previous research has indicated there is a strong, negative correlation between grain yield and protein. The general rule is that if protein is below 11% it can be assumed that yield will be sub-optimal, given the growing season and the crop, and some yield potential could have been missed. Unfortunately, knowing the grain protein only allows growers to look retrospectively, rather than react during the season. It is certainly important that all cereals have grain protein recorded, even if they are for feed and do not go through receivals, because this is a really good guide to N management for the crop.

2) Selecting the right source - solid vs liquid N:

This trial looked into three different forms of nitrogen - granular urea, urea ammonium nitrate (UAN) and liquid urea. The data indicated there were no significant differences between the three products. This may be related to the 2013 season and the result could differ in drier finishes.

In terms of comparing liquid N and urea, there are a number of factors that growers still need to take into consideration. Granular urea is by far the cheapest form of N, but it can show an increase in losses via volatilisation when compared to liquid N.

Spreading widths are getting wider and there may be a case for considering fluid fertiliser sources because they can be applied through a boomspray at the correct width compared to a spinning disc spreader - highly reliant on limited wind, good machine set-up and a quality product.

Crop scorch is a problem to consider, despite not being an issue in these trials. When applying liquid N fertiliser there are some simple rules to follow to minimise scorch or leaf burn:

  • Use stream jets as opposed to flat fan nozzles.

  • Do not apply to water-stressed crops.

  • Do not apply to wet foliage (including dew).

  • Do not apply in windy weather when the streams will break up into small drops.

  • Do not apply UAN in temperatures more than 20oC. Applications are best applied in the early evening.

  • Do not apply after frost. Wait at least one day for each day of frost.

  • Do not apply when temperatures are above 25oC. Applications are best applied in the early evening.

  • Do not apply within three days of other foliar treatments.

3) Selecting, assessing the right application rate:

Assess the N supply from the soil, which includes residual N, and also an estimation of what may be mineralised.

4) Estimate a realistic yield potential:

N removal by wheat is about 20-25kgN/t of grain, with N use efficiency up to 40-50%. Therefore, a crop with a 4t/ha target yield will need to be supplied with between 140kgN/ha and 150kgN/ha. This will be supplied from soil or the spreader, or a combination of the two.

5) Selecting the right time to apply fertiliser to optimise yield:

The main timing for N fertiliser is just before its maximum demand by the crop, which is during early stem extension. This project has shown that an inadequate supply of N before GS32 can still be rectified by treatments, up to and including GS39, as long as seasonal moisture and rainfall conditions after this application are suitable for enhanced yield. Applications after GS39 can increase yield in some cases, but are more likely to start having a greater effect on grain protein.

Recommendations

Recommendations for future work

Because of the late start to this project, a GS32 timing in New South Wales (NSW) was missed and even though two rates of N (25kg N/ha and 50kg N/ha) on top of previous treatments were applied, many sites were under fertilised in 2014. The project aim of getting at least some samples from each trial site (>12% protein) did not happen.

Achievements/Benefits

Background

Growers and agronomists have to make a number of key, tactical decisions each season in respect of overall N management. These include such things as:

  • Application rates, based on seasonal conditions and their effect on yield potential.

  • The price of N fertiliser and how it will impact on the potential dollar return/ha.

  • The timing of applications and the ability to get N into the crop with sufficient rainfall or moisture, especially when applied later in the season.

In the 2013 season, there was good soil moisture in medium and high rainfall areas. The majority of climate models predicted a positive outlook for spring. Taking advantage of the opportunity to increase yields, given these conditions, has been identified as a high priority issue by the GRDC HRZ RCSN.

The low protein levels of wheat in 2012 would suggest that the optimum N requirements were not being met and, therefore, could limit the potential yield. The above average yields in 2012, combined with low protein grain, indicated that soil N supply would also be low. This was confirmed by the results of deep soil N tests before sowing and those taken in recent months.

Given the dry summer, little mineralisation of N and a wet winter, it is likely that protein levels of wheat could again be low. Another factor contributing to lower available N inputs into the system is the lack of N-fixing break crops. The consequence of lower mineral N levels is that N fertiliser input requirements will be significantly higher (than previously experienced) to achieve yield potential and grain quality (protein and screenings). The timing of N applications is also important to ensure that supply of N matches that of crop demand, and that deferring investments in response to seasonal conditions can be made.

The need for additional N fertiliser inputs in 2013 to achieve yield potential at accepted grain receival standards for protein concentration is not widely understood and/or under-estimated by the majority of agronomists and growers. The type of N fertiliser applied, whether as a liquid or in solid form, has not been researched when applied after GS32 because in many seasons the conditions are not suitable for further yield gains and grain protein enhancement.

Objectives

These trials will provide objective data to assist growers make decisions on late N applications from GS32 (second node detectable) through to GS70 (grain watery ripe) comparing solid urea with two forms of liquid N. This will demonstrate strategies growers can use in the future to achieve increased grain yields, while maintaining acceptable grain protein, in seasons where crops have adequate soil water. The trial objectives, updates, results and application of this information for N budgeting and decision-making will be extended through the farming systems and GRDC networks. The extension activities will include newsletters, field days, publication of trial results, ‘Ground Cover’ and HRZ RCSN members' networks.

Methodology

Eight trial sites were established and used a common set of protocols to evaluate the effect of N rates, products and application times on wheat yield and grain quality under a wide range of environmental conditions. The protocols were developed by the project coordinator with technical expertise and review provided by Rob Norton, Regional Director (Australia and New Zealand) of the International Plant Nutrition Institute. These standard protocols ensured consistency and limited the variables between the sites to improve the statistical validity of the trials across multiple locations.

Table 1: Trial sites background information

Cooperating Group

Site

Location

Variety

Sowing Date

Farmlink

Temora

Southern NSW

Bolac

15 May

SFS

Inverleigh

Western Districts VIC

Derrimut

25 May

SFS

Murnong

Western Districts VIC

Revenue

3 June

SFS

Westmere

Western Districts VIC

Forrest

22 May

MFMG

Conmurra

South East of SA

Revenue

30 May

MFMG

Wolseley

South East of SA

Axe

11 June

SFS

Rokeby

Midlands- TAS

Revenue

28 May

SFS

Woodbury

Midlands- TAS

Revenue

17 May

The trials were placed into existing areas of wheat and set up to start the first application at GS32. This would be applied in addition to what had already been applied, up to that point, by the grower. Unfortunately, the late start meant the project the site at Temora missed out on the GS32 application as it was already more advanced than this in late August.

The trial designs were the same for seven of the eight experiments, and so the data were analysed using a factorial analysis of variance. The factors tested were seven sites, four timings, three sources and two rates. Analysis was carried out using Minitab-14. Grand means for the main treatments and main factor effects presented are from these seven sites. The data for each site were derived from this analysis, as this provided the greatest precision in estimating the treatment effects at the site. The data for the Temora site were analysed individually.

Where significant effects were noted from the analysis of variance, the means were compared using a least significant difference at p<0.05.

1) Rate

Two nitrogen rates – 25kgN/ha and 50kgN/ha (these were additional to what had been applied up to GS32).

2) Product type

Three nitrogen products:

  • UAN (42.5%N).

  • Granular urea (46%N).

  • Liquid urea (24%N).

  • UAN and liquid urea applied through streaming nozzles at GS32 and GS39 and through fat fan nozzles at GS55 and GS70.

  • Urea was top dressed.

3) Timing

Application times:

  • GS32 - second node detectable.

  • GS39 - flag leaf fully emerged.

  • GS55 - head 50% emerged on main stem.

  • GS70 - grain watery ripe.

4) Control

Whatever the grower had applied up to and including GS32

Table 2: Trial site descriptions and N management prior to GS32 treatments

Site

Location

Sowing
Date

Variety

Previous
Crop

Pre GS32 N
(kg/ha)

Soil Type

Soil N
(kg/ha)*

Temora

NSW

15 May

Bolac

Wheat

80

Clay Loam

 

Inverleigh

VIC

25 May

Derrimut

Canola

84

Clay Loam

100

Murnong

VIC

3 June

Revenue

Wheat

45

Clay Loam

96

Westmere

VIC

22 May

Forrest

Canola

70

Grey Loam

115

Conmurra

SA

30 May

Revenue

Beans

45

Black Clay

 

Wolseley

SA

11 June

Axe

Canola

90

Clay

 

Rokeby

TAS

28 May

Revenue

Potatoes

36

Sandy Loam

103

Woodbury

TAS

17 May

Revenue

Poppies

100

Sandy Loam

 

* Deep N tests taken before the first trial application applied (Oct 2013)

Additional information

Results

Eight sites were selected from across the southeastern Australian high rainfall zone, although the site at Temora (NSW) was not particularly high yielding due to drought. The site yields and proteins for the 'Control' or Farmer practice treatments are shown in the Table below.

Table 3. Site mean yields, grain protein and quality for the control treatments (Grower Practice). Grain values are adjusted to 12.5% moisture content. N removed is in the grain only.

Site

Yield
(t/ha)

Protein
(%)

N Removed
(kgN/ha)

Test Weight
(kg/hl)

Screenings
(%)

Temora

2.62

13.2

60

76.8

3.5

Conmurra

5.04

11.9

105

73.4

4.5

Wolseley

5.18

11.8

107

83.5

1.2

Inverleigh

6.10

9.8

105

77.6

10.7

Murnong

3.71

7.2

47

73.4

7.8

Westmere

5.39

10.5

99

75.8

2.9

Rokeby

7.70

7.8

105

76.2

1.6

Woodbury

9.27

8.7

141

78.8

14.4

Means

5.63

10.1

96

77.0

5.8

  • There were high screenings (<2 mm) in the controls at most sites except Rokeby and Wolseley.
  • The highest grain protein was at Temora. This is most likely the impact of drought and the addition of 80kg N/ha pre GS32.
  • Conmurra, Wolseley and Westmere all delivered grain proteins above 10.5% so the pre GS32 N status of these paddocks was probably quite good.

The data were analysed to assess if there were significant responses to N, comparing the control, where no additional nitrogen was applied after GS32, with the applied treatments.

Firstly the data were analysed by site and as a group to compare the mean N response of all the treatments to the control yield and protein percent. The results of these analyses are given in Table 4.

Table 4. Mean effects of N treatments compared to the control or grower practice

 

Yield
(t/ha)

Protein
(%)

N Removed
(kgN/ha)

Test Weight
(kg/hl)

Screenings
(%)

Temora

ns

*****

ns

ns

Conmurra

*

ns

*

ns

ns

Wolseley

ns

ns

ns

ns

ns

Inverleigh

****

*

ns

ns

Murnong

*******

ns

*

Westmere

ns

***

ns

ns

ns

Rokeby

ns

**

ns

ns

ns

Woodbury

ns

ns

ns

*

ns

Means

     
FP

5.63

10.1

99

77.0

5.8

FP+N

5.92

10.6

108

76.7

5.9

* p<0.10. ** p<0.05, ***p<0.001

When considered across all treatments, there were yield responses at three of eight sites, and protein responses at five of eight sites. This does not necessarily mean there were no N responses as some of the sites had individual treatments that were significantly different to the control but the N treatment values are the means of all the rates, timings and sources used. The mean response overall was 0.29t/ha and a protein increase in 0.5% The added N (mean of 37.5kg N/ha) showed an average recovery of 24% in these experiments. There were few effects of the additional N on screenings or hectolitre weights.

In summary, across these sites, there were more protein responses than yield responses.

Figure 1. Effect of Nitrogen (combination of timing, rate and type) on grain yield across eight sites. Pairs of site means followed by the same letter do not significantly differ (p<0.05).

Figure 2. Effect of Nitrogen (combination of timing, rate and type) on grain protein across eight sites First of site means followed by the same letter do not significantly differ (p< 0.05).

Multi-site Analysis-Response to the time, rate and type of N.
The data set comprised responses to four application times, two rates and three N sources. Grain yield (t/ha), grain protein (%), nitrogen removed in produce (kg N/ha), hectolitre weight (kg/hl) and the screenings (%) were collected and analysed using a balanced factorial (4*2*3) analysis of variance for seven of the eight sites. At the Temora site, the earliest N application was not undertaken at GS32, so the analyses there was a 3*2*3 analysis of variance. In addition, the seven sites where there were balanced data were analysed as a 7* 4* 2* 3 analysis of variance.

The overall analyses showed main treatment effects (Table 4). The seven sites had different responses due to N source/rate/time combinations on all five variables measured. Overall, there were a few yield effects due to any factor other than site, although there was a weak effect of rate. Grain protein was affected by the timing and rate of N applied, and there were different responses at different sites (Site*Time interaction), and also different responses to the N sources used across sites.

Table 5. Analysis of variance results for seven sites, four timings, two rates and three sources on grain yield, grain protein, nitrogen removal, hectolitre weight and screenings.

 

Yield

Protein

Nrem

HLW

Screenings

Site

***************

Timing

ns

******

ns

Rate

**********

ns

Source

ns

ns

ns

ns

*

Site*Time

ns

***

ns

***

ns

Site*Source

ns

**

ns

*

ns

Site* Rate

ns

***

ns

ns

Time*Source

ns

*

ns

ns

ns

Time* Rate

ns

ns

ns

***

ns

Rate* Source

ns

ns

*

ns

ns

Time*Rate*Source

ns

ns

ns

*

ns

* p<0.10. ** p<005, ***p<0001

Grain hectolitre weights (i.e. test weight) were affected by a range of factors in the analyses, but these changes were generally small (<1 kg/hl). At Conmurra, Murnong, and Temora, test weights were all below 76 irrespective of the N treatment. At the other sites, test weights were all above 76 irrespective of N treatments.

The percentage screenings in the grain samples were generally unaffected by any of the treatments, although there was a weak effect of different sources.

Effect of N Rate

N rate had a significant effect on grain protein and test weights across seven of the eight sites and other treatments (Table 6). Temora was not included in this part of the analysis, so the N0 data differ between Table 1 and Table 5.

Table 6. The effect of N rate on grain yield, protein, N removal and hectolitre weight averaged across seven sites and all other N treatments.

Rate

Yield

Protein

Nrem

HLW

N0+

5.24

8.6

92.0

67.3

N25

6.20

10.0

111.5

76.7

N50

6.30

10.4

116.1

77.0

 *******

***

* p<0.10. ** p<005, ***p<0.001
+Ni 1 N treatments are the means of sites other than Temora

The 50kg N/ha rate had a larger effect on grain protein than the 25kg N/ha rate. Application rate also increase N removal, and the marginal nitrogen use efficiency across all these experiments were 36%for the 25kg N/ha and 28%for the 50kg N/ ha rates.

Effect of Timing

Timing had a significant effect on protein response but not grain yield. In the higher yielding sites, it seems likely that the N supply before GS32 was adequate, and the main effect of the additional N was to increase grain protein rather than yield. Even so, the average size of the increase was small (approx. 0.4%) and was only seen in applications made at GS55. Application at GS39 had a smaller increase, and the applications as GS70 were too late to affect grain protein. There was only a weak interaction between N rate and timing, so that the rate effects did not differ at different times - so there was no strong indication that later applications required higher (or lower) rates than earlier applications.

Table 7. The effect of timing of N application on grain yield, protein, N removal and hectolitre weight averaged across seven sites and all other N treatments.

Timing

Yield

Protein %

Nrem

HLW

GS32

6.22

10.10

112.5

76.9

GS39

6.35

10.17

114.9

76.8

GS55

6.25

10.37

115.7

77.1

GS70

6.17

10.12

112.1

76.7

LSD (p<0.05)

ns

0.12

3.0

ns

Figure 3. Effect of Nitrogen timing (combined rate and type) on grain protein across eight sites. Means followed by the same letter do not significantly differ (p<0.05).

Effect of Source

The response to additional N occurred largely irrespective of the type used although the effects seen did vary from site to site. Table 8 shows the response to the two fluid N sources - UAN and urea, compared to granular urea. There was no difference in protein concentration at Conmurra, Murnong, Rokeby and Westmere, but the granular source resulted in decreased protein at Temora and Woodbury. At Inverleigh and Wolseley, the granular urea resulted in a protein increase compared to the fluid N sources. Again, these differences are on average only very small.

Table 8. The effect of N fertiliser type on grain protein percent at eight sites. Values are the means of two N rates and four N timings.

Site

UAN

Urea-Liquid

Urea-Granular

Significance (p<0.05)

Conmurra

11.6

11.8

11.6

b

Inverleigh

10.6

10.8

10.9

d

Murnong

8.0

8.0

8.2

g

Rokeby

8.5

8.3

8.5

f

Temora

14.6

14.5

13.5

a

Westmere

11.3

11.3

11.2

c

Woodbury

11.8

12.0

11.5

b

Wolseley

9.2

9.4

9.6

e

LSD (p<0.05)

0.29

 

Means followed by the same letter do not significantly differ (p<0.05).

Site by site analysis
Each individual site was also analysed for effects among the N strategies, and these results are presented in the following section. The focus is on the yield and protein response, particularly to timing, which was significant at six of the eight sites (5 p<0.05, 1 p<0.10). Rate differences were also significant at seven of the eight sites (5 p<0.05, 2 p<0.10) but there were few interactions to rate with timing.

Temora NSW

  • Significant (P=0.05) increase in grain protein application at GS39.
  • Yield increase to N at GS55 compared to N applied GE39.

This was the lowest yielding of all the sites, and showed a significantly lower grain protein concentration with later, rather than earlier N applications. Conversely, the grain yield was higher with the later application of N when compared to the earlier application. This pattern of response is consistent with a dry late winter/early spring, and then some recovery from late rains which were coincident with the later N application.

Table 9. Summary table of maximum and minimum values

 

Value

Units

Timing

Rate (kg N/ha)

Type

P<0.05

Highest yielding treatment

2.76

t/ha

GS55

25

Liquid Urea

No

Lowest yielding treatment

2.48

t/ha

GS39

50

UAN

No

Highest Protein

15.3

%

GS39

50

Liquid Urea

Yes

Lowest Protein

12.2

%

Control

  

Yes

Highest Test Wt

78.1

kg/hl

GS70

25

Urea

Yes

Lowest Test Wt

73.0

kg/hl

GS39

50

UAN

Yes

Highest Screenings

8.3

%

GS39

50

Liquid Urea

Yes

Lowest Screenings

1.9

%

Control

  

Yes

Figure 4. Effect of Nitrogen timing (combined type and rate) on grain yield (bars) and protein (line) - Temora. Means followed by the same letter do not significantly differ (p<0.05).

Conmurra SA

  • Small effect of adding extra N on yield over control

There were no significant differences seen in the timing, rate or type of N on yield or screenings. Protein concentration was only weakly affected by the timing - with the highest at GS55. There were very few other effects noted at this site due to the treatments applied.

This was a site with very high soil organic matter and it received moderate N before GS32. This high soil organic matter content would be likely to supply large amounts of N through in-crop mineralization, and so there is likely to be little or no N limitation. Even so, all post GS32 applications increased yield over the control.

Table 10. Summary table of maximum and minimum values

 

Value

Units

Timing

Rate (kg N/ha)

Type

P<0.05

Highest yielding treatment

6.32

t/ha

GS55

25

Liquid Urea

No

Lowest yielding treatment

4.98

t/ha

GS70

25

Urea

No

Highest Protein

12.33

%

GS55

50

Liquid Urea

Yes

Lowest Protein

11.25

%

GS70

25

UAN

Yes

Figure 5. Effect of Nitrogen timing (combined type and rate) on grain yield (bars) and protein (line) - Conmurra. Means followed by the same letter do not significantly differ (p<0.05).

Wolseley SA

  • No yield response, no protein response.

This was the only site where there was no effect of the additional N on either yield or protein. There were no effects of N on any of the parameters tested at this site, which was relatively late sown compared to the other sites. This would suggest that for Axe, sown in June, with 90kg N/ha applied pre-GS32, the yield potential had already been achieved. What is surprising, however, is that the grain protein content was not affected by increasing the rate or delaying the timing.

Table 11. Summary table of maximum and minimum values

 

Value

Units

Timing

Rate (kg N/ha)

Type

P<0.05

Highest yielding treatment

5.37

t/ha

GS39

25

Urea

No

Lowest yielding treatment

4.67

t/ha

GS32

50

Liquid Urea

No

Highest Protein

12.4

%

GS39

50

Liquid Urea

No

Lowest Protein

10.68

%

GS55

25

Urea

No

Figure 6. Effect of Nitrogen timing (combined type and rate) on grain yield (bars) and protein (line) - Wolseley. Means followed by the same letter do not significantly differ (p<0.05).

Inverleigh VIC

  • Significant (P=0.05) effect of additional N on yield from GS32 timing
  • Significant (P=0.05) increase in protein from applications made at GE39 and GE55 compared to GS70.
  • Significant (P=0.05) increase in protein from using Urea compared to UAN when applied across all timings and rates.

At this site there were few other effects seen. Grain yield was significantly higher from a GE32 application compared to all other treatments except GE50. Grain protein concentration was significantly higher with N applied at GS39 and GS55 but not at GE32 (too early) or GS70 (too late). This site had very high screenings overall, but this was not increased by the extra N applied.

Table 12. Summary table of maximum and minimum values

 

Value

Units

Timing

Rate (kg N/ha)

Type

F<0.05

Highest yielding treatment

7.21

t/ha

GS32

50

UAN

Yes

Lowest yielding treatment

5.81

t/ha

GS70

25

Urea

Yes

Highest Protein

12.6

%

GS55

50

Liquid Urea

Yes

Lowest Protein

10.5

%

Control

  

Yes

Figure 7. Effect of Nitrogen timing (combined type and rate) on grain yield (bars) and protein (line) - Inverleigh. Means followed by the same letter do not significantly differ (p<0.05).

Figure 8 below shows the differences in grain protein using the three sources of N evaluated. The means presented are from the combined rate and timing values. The interaction between timing, source and rate is shown in Figure 9 below. Although the highest yielding treatment is 50kg N/ha at GS32, using UAN it is not statistically (P=0.05) higher yielding than most of the GS32 treatments, two GS39 and GS55 treatments and one GS70 treatment.

Figure 8. Effect of Nitrogen type (combined rate and timing) on grain protein - Inverleigh. Means followed by the same letter do not significantly differ (p<0.05).

Figure 9. Yield of the Nitrogen treatments - Inverleigh. Means followed by the same letter do not significantly differ (p<0.05).

Murnong VIC

  • Significant (P=.05) effect of additional N on yield from GS39 timing compared to GS70 and control.
  • Significant (P=.05) increase in protein from application made at GS55
  • Yield dilution on protein very obvious at GES9.

This site had the lowest grain proteins of all the eight sites evaluated, but yields were the second lowest, which suggests that N was limiting on the site. Nitrogen removal by wheat is around 20-25kg per tonne of grain, with a nitrogen use efficiency of 40 to 50% Therefore, a crop with a 4t/ha target yield will need to be supplied with between 140 and 160kg N per hectare.

The deep soil N test showed there was 50kg N/ha before sowing, and there was an additional 45kg N/ha that was applied by the end of August, the 4t/ha wheat crop will have needed to be supplied with an additional 45 to 65kg N to meet its potential. While in-crop mineralisation may have made up some of this deficit, it seems that restricted supply resulted in the 4t/ha yield target being met, but seasonal conditions were probably conducive to a yield of 6-7t/ha, so very low protein levels resulted from the limited N supply.

A significant yield response to extra N over the control was seen from applications at both GS32 and GSS9, with the largest responses overall at GE39 timings. Protein levels were still low and this was likely to be due to the highest rate of N at 50kg N/ha not being high enough at this site. The GS70 N applications showed a slight, but not statistically significant, lower yield.

Table 13. Summary table of maximum and minimum values.

 

Value

Units

Timing

Rate (kg N/ha)

Type

P<0.05

Highest yielding treatment

5.21

t/ha

GS39

50

Liquid Urea

Yes

Lowest yielding treatment

3.25

t/ha

GS70

25

UAN

Yes

Highest Protein

9.1

%

GS55

50

Urea

Yes

Lowest Protein

7.2

%

GS39

25

UAN

Yes

Figure 10. Effect of Nitrogen timing (combined type and rate) on grain yield (bars) and protein (line) - Murnong. Means followed by the same letter do not significantly differ (p<0.05).

Westmere VIC

  • Small yield response from a GS32 application only significantly different to the GS70 timing
  • Significant (F=.05) increase in protein from application made at GS55

The main effect seen in response to added N was an increase in grain protein concentration with the N applied at GS55 (11.2 to 11.9%). Later applications had no significant effect. There was a weak trend with later applications having smaller yield response.

The grain protein content suggests that N supply pre GS32 was probably adequate for yield, but the GS55 protein response suggests that for an AFW receival standard a late season application makes sure a grower hasn't misjudged the potential of the season and gained more yield than expected but at the expense of a minimum 10.5%protein. At this site the Forrest wheat just got in at 10.5%>!

Table 14. Summary table of maximum and minimum values

 

Value

Units

Timing

Rate (kg N/ha)

Type

P<0.05

Highest yielding treatment

6.00

t/ha

GS39

25

Liquid Urea

Yes

Lowest yielding treatment

5.00

t/ha

GS55

25

Urea

Yes

Highest Protein

12.6

%

GS55

50

Liquid Urea

Yes

Lowest Protein

10.5

%

Control

  

Yes

Figure 11. Effect of Nitrogen timing (combined type and rate) on grain yield (bars) and protein (line) - Westmere. Means followed by the same letter do not significantly differ (p<0.05).

Rokeby TAS

  • No statistically significant yield response although the highest yield came from a GS39 application
  • Significant (P=.05) increase in protein from application made at GS55

Grain protein concentration increased above the control in response to all applications, with the late applications of N at GS55 and GS70 giving a larger increase than the earlier applications. This may be because of a longer more active green canopy at this site, which was the second highest yielding site overall.

Grain proteins overall were less than 10%and the rate response to grain protein seen here (Figure 12 below) suggests that there may have been even higher yields with additional N. The pre-GS32 N used was only 35 kg N/ha, although there was 100 kg N/ha in the profile at sowing.

The highest yields came from applications at GS39 (see figure 14 below) but many other combinations of timing and product type also gave a similar increase.

Table 15. Summary table of maximum and minimum values.

 

Value

Units

Timing

Rate (kg N/ha)

Type

P<0.05

Highest yielding treatment

8.67

t/ha

GS39

50

Urea

No

Lowest yielding treatment

6.88

t/ha

GS70

25

Urea

No

Highest Protein

9.1

%

GS55

50

Urea

Yes

Lowest Protein

7.7

%

Control

  

Yes

Figure 12. Effect of Nitrogen timing (combined type and rate) on grain yield (bars) and protein (line) - Rokeby. Means followed by the same letter do not significantly differ (p<0.05).

Figure 13. Effect of Nitrogen rate (combined type and timing) on grain yield (bars) and protein (line) - Rokeby. Means followed by the same letter do not significantly differ (p<0.05).

Figure 14. Effect of Nitrogen timing and type (combined rate) on grain yield - Rokeby. Means followed by the same letter do not significantly differ (p<0.05).

Woodbury TAS

  • Early Nitrogen applied before GS32 gave the best yield response
  • Although not statistically significant there was a protein response to GS39 and GS55 applications of N.

This was the highest yielding site, was one of the earliest sown and had to 100kg N/ha in three splits applied before GS32.There were progressively smaller responses to N as applications became later, but grain protein concentration increased with the GS39 and GS55 applications giving the largest increases. This site also had the highest screenings, although test weight was still above 76 kg/hl.

Table 16. Summary table of maximum and minimum values.

 

Value

Units

Timing

Rate (kg N/ha)

Type

P<0.05

Highest yielding treatment

9.51

t/ha

GS32

25

UAN

No

Lowest yielding treatment

8.06

t/ha

GS39

25

UAN

No

Highest Protein

10.0

%

GS32

50

Urea

Yes

Lowest Protein

8.7

%

Control

25

UAN

Yes

Figure 15. Effect of Nitrogen timing (combined type and rate) on grain yield (bars) and protein (line) - Woodbury. Means followed by the same letter do not significantly differ (p<0.05).

Published Date
2 July 2015
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