Postgraduate Showcase 2016

Transcription

1 The UWA Institute of Agriculture Postgraduate Showcase 2016 Seasonal factors influence the benefit of break crops under long term no tillage Nathan Craig, Ken Flower (UWA), Michael Renton (UWA), Phil Ward (CSIRO), Gupta V.V.S.R (CSIRO)

2 Broad context: Wheat production Western Australia 60% of area sown to crop Nitrogen supply and grain yield Focus: Change in farming system

3 Change in farming system: no tillage Conventional tillage No tillage

4 Crop residue: what is it? Grain removed Crop residue remains

5 Crop residue: Importance Source of soil organic matter Decomposes to release nutrients Mineralisation the last step to release nutrients

6 Crop residue: Importance Source of soil organic matter Decomposes to release nutrients Mineralisation the last step to release nutrients Nitrogen: a requirement and a product Carbon to nitrogen ratio Mineralisation vs Immobilisation

7 Under long term no tillage: High levels of crop residue Accumulation over many years Mixture of crop residue types

8 Under long term no tillage: High levels of crop residue Accumulation over many years Mixture of crop residue types Effect of crop rotation on nitrogen supply and grain yield

9 The long term no tillage trial site Established 2007 Two contrasting crop rotations Rotation wheat chickpea canola Monoculture wheat wheat wheat

10 The long term no tillage trial site Established 2007 Two contrasting crop rotations Rotation wheat chickpea canola Monoculture wheat wheat wheat Two nitrogen fertiliser rates Nil 44 kg/ha (11 at sowing, 33 in mid July) All phases of the crop rotation were sown in each year

11 Set the scene:

12 Set the scene: Seasonal rainfall (mm)

13 Set the scene: Soil moisture (% v/v)

14 Set the scene: Soil temperature Maximum Minimum

15 Set the scene: Crop residue (kg/ha) Year Crop type Biomass Carbon : nitrogen ratio 2013 Rotation 3855 a 37 a Monoculture 6771 b 47 ab

16 Set the scene: Crop residue (kg/ha) Year Crop type Biomass Carbon : nitrogen ratio 2013 Rotation 3855 a 37 a Monoculture 6771 b 47 ab 2014 Rotation 3237 a 58 b Monoculture 3327 a 83 c

17 The scene is set! Rainfall Two contrasting summer/growing season combinations Temperature High temperature differentials in summer Low minimum soil temperature in winter Crop residue High immobilisation potential in 2014

18 Nitrogen mineralisation: Measurement Summer Soil cores to 120 cm depth in May Compare to post harvest Growing season Raison tube method May to October period

19 Nitrogen mineralisation: Raison tubes N mineralisation Raison tube method in situ measurement A 0 10 cm May to October period B Annual change in soil nitrogen soil cores to 120 cm depth taken at sowing

20 Growing season mineralisation (kg N/ha)

21 Growing season mineralisation (kg N/ha)

22 Growing season mineralisation (kg N/ha) b a

23 Growing season mineralisation (kg N/ha) b a

24 Remember summer rainfall?

25 Soil nitrogen after summer (kg N/ha) Year Nitrogen applied Treatment Soil mineral N cm depth 2013 Nil Rotation 105 b Monoculture 54 a 44 kg Rotation 103 b Monoculture 74 a

26 Soil nitrogen after summer (kg N/ha) Year Nitrogen applied Treatment Soil mineral N cm depth 2013 Nil Rotation 105 b Monoculture 54 a 44 kg Rotation 103 b Monoculture 74 a 2014 Nil Rotation 44 Monoculture kg Rotation 57 Monoculture 63

27 Disease influence: Monoculture Root diseases one third higher Rhizoctonia solani Pratylenchus neglectus Leaf disease three times higher Septoria nodorum blotch Yellow spot (Pyrenophora tritici repentis) Flag smut (Urocystis agropyri) 2013 more severe than 2014

28 Wheat grain yield (kg/ha) Nil nitrogen 44kg/ha nitrogen

29 Wheat grain yield (kg/ha) Nil nitrogen 44kg/ha nitrogen

30 Components of yield Year Crop Nitrogen applied Plants/m 2 Heads /m 2 Seed weight (milligrams) 2013 Rotation Nil kg/ha 170 Monoculture Nil kg/ha 186

31 Components of yield Year Crop Nitrogen applied Plants/m 2 Heads /m 2 Seed weight (milligrams) 2013 Rotation Nil kg/ha Monoculture Nil kg/ha

32 Components of yield Year Crop Nitrogen applied Plants/m 2 Heads /m 2 Seed weight (milligrams) 2013 Rotation Nil kg/ha Monoculture Nil kg/ha

33 Components of yield Year Crop Nitrogen applied Plants/m 2 Heads /m 2 Seed weight (milligrams) 2013 Rotation Nil kg/ha Monoculture Nil kg/ha Rotation Nil kg/ha 110 Monoculture Nil kg/ha 108

34 Components of yield Year Crop Nitrogen applied Plants/m 2 Heads /m 2 Seed weight (milligrams) 2013 Rotation Nil kg/ha Monoculture Nil kg/ha Rotation Nil ab 44 kg/ha c Monoculture Nil a 44 kg/ha bc

35 Components of yield Year Crop Nitrogen applied Plants/m 2 Heads /m 2 Seed weight (milligrams) 2013 Rotation Nil kg/ha Monoculture Nil kg/ha Rotation Nil ab kg/ha c 41 Monoculture Nil a kg/ha bc 45

36 Grain nitrogen uptake (kg N/ha) Nil nitrogen 44 kg/ha nitrogen

37 Grain nitrogen uptake (kg N/ha) Nil nitrogen 44 kg/ha nitrogen

38 Under long term no tillage: Conclusions The largest effect of crop rotation on mineralisation was in summer ( extra 29 to 51 kg N/ha)

39 Under long term no tillage: Conclusions The largest effect of crop rotation on mineralisation was in summer ( extra 29 to 51 kg N/ha) Growing season mineralisation supplied 0 35 kg N/ha Crop residue carbon:nitrogen ratio Soil mineral N at seeding

40 Under long term no tillage: Conclusions The largest effect of crop rotation on mineralisation was in summer ( extra 29 to 51 kg N/ha) Growing season mineralisation supplied 0 35 kg N/ha Crop residue carbon:nitrogen ratio Soil mineral N at seeding Grain yield and nitrogen benefit of crop rotation was equal to 44 kg N/ha Nitrogen supply was a larger limiting factor than disease

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