Splitting of nitrogen in medium-high rainfall canola, Esperance 2015 trial report

Page last updated: Thursday, 18 April 2019 - 4:28pm

In general, as long as nitrogen is applied within eight weeks of sowing, there is no yield penalty.

How canola responds to nitrogen applied later than eight weeks has not been widely researched. Similarly how new generation canola such as Roundup ready (RR) hybrids respond to nitrogen has not been widely tested, particularly in low and medium rainfall areas.

Summary (key messages)

In this 2015 trial;

  • Economic response plateaued at 75kg N/ha – lower than grain yield (125kg N/ha).
  • Nitrogen applications at 12 and 14 weeks produced similar canola responses to N applied earlier in the year – but no added benefit.
  • OP TT and hybrid RR varieties had a similar response to nitrogen timing and rate.

Aim

To investigate the response to changing the nitrogen rate and changing the time of application. Canola yield and oil will be measured and RR hybrids will be compared with open-pollinated TT types (OP TT).

Trial details

  • Property: DAFWA site at Esperance Downs Research Station
  • Agzone 6, growing season rainfall (GSR) (May to October): 320mm, GSR + stored water (estimate): 387 mm, dry October of 17mm compared to LTA of 43mm
  • Soil type: gravelly sand (1.43% organic carbon)
  • Paddock rotation: cereal 2014, canola 2013, sub-clover pasture 2011 and sub-clover pasture 2010
  • 28 treatments: two cultivars (ATR Wahoo [TT open-pollinated variety] and Hyola 600 RR [RR hybrid variety]) x 14 N treatments (kg N/ha) with timing spread between seeding, and up to 14 weeks after sowing (see Table 1)
  • Three replicates
  • Sowing date: 28 April
  • Seeding rate: Target density 30 plants/m2 - ATR Wahoo 2.7kg/ha, Hyola 600RR 1.9kg/ha
  • Fertiliser: 400kg/ha of gypsum (17% Ca, 14% S) top-dressed over whole paddock in late March. 100kg/ha of Superphos at seeding, 200kg/ha of Muriate of Potash top-dressed over whole site 4 June, 4kg MnSO4/ha sprayed on 29 July, and 1kg ZnSO4 sprayed on 4 August.

Treatment detail

Table 1 Treatment details
Treatment number Name Seeding 0 to 8 weeks 12WAS 14WAS
1 Seeding 0 0 0 0
2 2-way split 15 35 0 0
3 2-way split 15 60 0 0
4 2-way split 15 85 0 0
5 2-way split 15 110 0 0
6 3-way split 15 10 25 0
7 3-way split 15 35 25 0
8 3-way split 15 35 50 0
9 3-way split 15 60 25 0
10 3-way split 15 60 0 25
11 4-way split 15 35 25 25
12 3-way split 15 85 25 0
13

 

3-way split

15 85 0 25
14 4-way split 15 35 50 25

Seeding N applied as Urea, top-ups applied as liquid N.

Assumptions used in gross margins

  • Oil bonus +/- 1.5% per unit of oil (%) either side of 42%, with no oil ceiling.
  • Additional costs such as seeding, harvest, insecticides assumed to be $100/ha.
  • Nitrogen costs $1/kg solid and $1.53/kg for foliar, application costs $8/ha.
  • RR costs – seed $61/ha, herbicides $45/ha, grain worth $498/t (decile 5 pricing).
  • TT costs – seed $5/ha, herbicides $60/ha, grain worth $518/t.

Results

Table 2 Grain yield (GY, kg/ha), oil concentration in seed (%), oil yield (kg/ha) and gross margin (GM, $/ha) of canola in response to applied N at Gibson in 2015. Values followed by the same letters are not significantly different.
N GY Oil Oil yield GM
0 2.08a 48.4c 1009a 894a
50 2.42b 48.2bc 1169b 1000b
75 2.63c 48.3c 1269c 1068c
100 2.71d 48.0ab 1298d 1076c
125 2.81e 47.8a 1342e 1082c
- - - - -
N <0.001 0.004 <0.001 <0.001
Table 3 Grain yield (GY, kg/ha), oil concentration in seed (%), oil yield (OY, kg/ha) and gross margin (GM, $/ha) of canola in response to split applications of N at Gibson in 2015. Values followed by the same letters are not significantly different. Values followed by the same letters are not significantly different.
Timing N Treatment Total N GY Oil OY GM
Seeding 0N 0 2.08 a 48.4 c 1009 a 894 a
2-way split 15N 35N 50 2.44 b 48.4 c 1179 b 1013 bc
2-way split 15N 60N 75 2.62 c 48.5 c 1269 c 1077 de
2-way split 15N 85N 100 2.72 defg 48.1 abc 1309 cd 1089 de
2-way split 15N 110N 125 2.83 hi 47.8 ab 1352 de 1104 e
3-way split 15N 10N 25N 50 2.41 b 48.1 abc 1106 b 986 b
3-way split 15N 35N 25N 75 2.64 cd 48.2 bc 1270 c 1074 de
3-way split 15N 35N 50N 100 2.74 fgh 47.9 ab 1313 cde 1088 de
3-way split 15N 60N 25N 100 2.65 cde 48.1 abc 1273 c 1040 cd
3-way split 15N 60N 0N 25N 100 2.73 efg 47.9 ab 1309 cd 1078 de
4-way split 15N 35N 25N 25N 100 2.69 cdef 48 abc 1289 c 1047 cd
3-way split 15N 85N 25N 125 2.83 i 47.9 ab 1357 e 1101 e
3-way split 15N 85N 0N 25N 125 2.8 ghi 48 abc 1346 de 1081 de
4-way split 15N 35N 50N 25N 125 2.76 fghi 47.6 a 1314 cde 1041 cd
- - - - - - -
P N treatment - <.001 0.049 <.001 <.001
P Variety x N treatment - 0.239 0.198 0.371 0.305
L.S.D N treatment - 0.089 0.5 45.8 51
Table 4 Grain yield (GY, kg/ha), oil concentration in seed (%), oil yield (kg/ha), gross margin ($/ha), total dry matter at maturity (TDM, kg/ha), harvest index (HI,%) and protein in seed (%) of two canola varieties at Gibson in 2015
Variety GY Oil Oil Yield GM TDM HI Protein
ATR Wahoo 2.59 47.5 1232 1065 11473 23 20
Hyola 600RR 2.68 48.6 1303 1037 11733 23 19.5
- - - - - - - -
P 0.099 0.006 0.036 0.228 0.596 0.661 0.056
L.S.D 0.129 0.37 59 69 1795 3 0.5

Conclusion

At Gibson in 2015, we observed a positive grain yield and oil yield response up to 125kg N/ha. Once we took into account the cost of N we observed positive gross margin response up to 75kg N/ha, where the rate of return for investment in N would have been appoximately $3.

For 50N and 75N split application at seeding/eight weeks produced the same yield, oil, oil yield and gross margin as split at seeding/8WAS/12WAS. For 100N and 125N split applications had similar responses.

Considering a scenario where a grower may have put on 75N within first eight weeks – and would they have observed a response to an extra 25N at 12 or 14 weeks, we observed no extra yield if you apply 25N at 12 weeks, but extra yield if applied at 14 weeks, less oil percentage if you apply 25N at 14 weeks, but no difference yield if applied at 12 weeks and no response to N applied at 12 or 14 weeks for oil yield or gross margins. It appears our late application treatments are being imposed upon too high a background of applied N and we probably need to conduct our late N treatments at lower rates of N, that is apply 50N within 8 weeks and compare extra 25N at 8, 10 12, 14 to 20 weeks.

With the exception of higher oil from Hyola 600RR, we found very little difference between varieties and no variety x N treatment interactions.

Acknowledgements

This trial (15ED22) is one of a series conducted throughout Western Australia as part of the GRDC/DPIRD co-funded project Tactical Break Crop Agronomy in Western Australia. Thanks to the Esperance RSU for trial management. Pam Burgess (DAFWA, Esperance) provided technical assistance to ensure all treatments and measurements occurred in a timely and accurate fashion.

Contact information

Mark Seymour
+61 (0)8 9083 1143
Raj Malik
+61 (0)8 9821 3247