Re-evaluating cover crops in semi-arid cropping in Australia

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1 Re-evaluating cover crops in semi-arid cropping in Australia John Kirkegaard, James Hunt, Jeremy Whish, Mark Peoples, Tony Swan SUSTAINABLE AGRICULTURE FLAGSHIP 1

2 Introduction and talk outline Background to Australian agriculture Cover crops why now? Brief Case studies West Mediterranean (winter rainfall) Southeast temperate (equi-seasonal) North subtropical (summer rainfall) Conclusions 2 APSIM & LUSO James Hunt 2

3 Australian dryland crop production Dry ( mm), infertile soils, unsubsidised agriculture CLERMONT GERALDTON MERREDIN 120 X Mixed farms (2000 ha) 1 crop/yr (May-Nov) Mean yield 2-3 t/ha 120 X X 0 DALBY 0 CONDOBOLIN MOOMBOOLDOOL WAGGA WAGGA ESPERANCE 0 ROSEWORTHY 0 HORSHAM 3

4 Farming system evolution Up to 1980s ley pastures grass/annual legumes (merino sheep for wool) cereals (wheat and barley) Pasture Wheat Barley Burn or remove residues + Repeated cultivation for weeds and seedbed 4

Farming system evolution Since 1990 - Intensification of

stubble retention Pasture Canola Wheat Wheat Lupin Wheat

5 Farming system evolution Since Intensification of cropping fewer, larger farms (2000 ha) increased crop area per farm (3.6% pa) less pasture, fewer sheep more crop diversity, no-till, stubble retention Pasture Canola Wheat Wheat Lupin Wheat The Millenium drought more cereals, less break crops wider rows and stubble retention = herbicide resistant weeds 5

6 Australian national wheat yield trends Kirkegaard et al., (2013) Agriculture, Ecosystem and Environment (online) 6

7 Why cover crops why now? Reported and anticipated benefits Soil cover and protection Structural improvement and improved water budget Soil N benefits (legumes) Weed management Disease management Recent drivers in Australia Pasture area has declined, more continuous no-till cropping Drought drives continuous cereals (80-90%) Costs of N fertiliser, reduced efficacy of selective grass herbicides Roper et al., (2012) Advances in Agronomy 117,

Case study 1 Cover crops in western Australia Primary Issues Low groundcover under no-till cropping in WA Emergence of herbicide tolerant grass weeds High N immobilisation in cereal crop residues

8 Case study 1 Cover crops in western Australia Primary Issues Low groundcover under no-till cropping in WA Emergence of herbicide tolerant grass weeds High N immobilisation in cereal crop residues Cover crop investigation Can a Black oat cover crop be grown to; (i) Maintain cover and improve water balance? (ii) Improve weed control? (iii) Reduce N immobilisation? Part of a larger systems experiments ( ) Flower et al., (2012) Field Crops Research, 132:

9 Case study 1 Cover crops in western Australia Rolled oat cover crop Harvested cereal crop OR 9 9

10 Case study 1 No effect on water balance Site/ Residue Yr 1 Evapotranspiration (mm) Drainage Treatment (t/ha) Year 1 Summer Year 2 (mm) Site 1 CC - Crop Cont. Crop Site 2 CC - Crop Cont. Crop Oat Cover crop did not increase summer cover cf cereal crop Cover had little impact on summer ET (high potential ET, sporadic rainfall) Little overall impact on water balance Ward et al., (2012) Field Crops Research, 132:

11 Case study 1 N, weeds, economics? Nitrogen Weeds No differences in soil N mineralisation between cover crop and cereals Subsequent crops would require similar N application Oat cover crops was effective for weed control, but similar to pasture Two years of cover crop required to control ryegrass (high levels) Killing by first week September needed to reduce seed set Economics Markedly reduced gross margins over 3 years (from $200/ha to $50/ha) Better Option Pasture with herbicide control of seed set; reduced crop stubble grazing 11 11

Case study 2 Legume brown manure in SE Australia Primary Issues Herbicide resistant grasses in cereal rotations High costs/risks of canola break crops in dry years Costs of N supply in continuous

12 Case study 2 Legume brown manure in SE Australia Primary Issues Herbicide resistant grasses in cereal rotations High costs/risks of canola break crops in dry years Costs of N supply in continuous cropping Low value/poor returns of legume for grain Cover crop investigations Can legume brown manures; (i) Provide cost-effective, low risk weed control? (ii) Boost N and water supply to subsequent crops? (iii) Provide part of a double-break option? Part of a larger crop sequence initiative (Dr Mark Peoples ) 12 12

13 At a reliable, high rainfall site with no HR weeds... Junee, 530mm rainfall - legume BM are difficult to justify 2011 Crop 2012 Crop $GM/ha 2011 $GM/ha 2012 Av. Ann. $GM/ha 2-Yr Profit/Cost Ratio Canola Wheat $1,200 $545 $ Lupin Wheat $455 $821 $ Wheat Wheat $511 $617 $ BM - Lupin Wheat -$150 $902 $ Opportunity cost of BM is not recovered in reliable environments 13 13

14 At a lower rainfall site with no HR weeds... Hopetoun, 350mm rainfall legume hay/bm competitive (4 yr) (Break-W-W-W) Long Short BM Benefits from water (Yr 2) and N supply (Yr 2-4) in a risky environment 14 Highlights of the GRDC WUE initiative James Hunt 14

.. 2012 Crop (Input) 2013 Crop $GM 2012 Canola - RR Wheat $1,259 Lupin Wheat $683

15 At a site with herbicide resistant weeds... Junee, 530mm rainfall but now with bad weeds Crop (Input) 2013 Crop $GM 2012 Canola - RR Wheat $1,259 Lupin Wheat $683 Wheat -High Wheat $257 Wheat -Low Wheat $250 BM - Lupin Wheat -$168 Wheat-Wheat??

16 At a site with herbicide resistant weeds... BM good weed control (=RR Canola), + N and water benefit 2012 Crop (Input) 2013 Crop $GM 2012 Cost of Herbicide ($/ha) Ryegrass panicles 2012 (/m 2 ) Seedbank 2013 (/m 2 ) Initial Soil N (kg/ha) Canola - RR Wheat $1,259 $ Lupin Wheat $683 $ Wheat -High Wheat $257 $ Wheat -Low Wheat $250 $ BM - Lupin Wheat -$168 $68 killed Note ryegrass panicles in October 2013 in wheat after RR canola under low input management (hay cut) = 512 panicles/m

17 Simulation studies Limitations of experiments Limited seasons, strong seasonal effects Difficult to study grass weeds in small plots Difficult to quantify long term effects Simulation and Optimisation APSIM break crop growth, water use, N-fixation, seasonal variability Land Use Sequence Optimiser (LUSO) weed bank dynamics (RIM), weed competition, economics Simulate sequences in APSIM for multiple years - output into LUSO Lawes and Renton (2010) Crop and Pasture Science, 61: APSIM & LUSO James Hunt 17 17

18 New ARG seeds (seeds/m²) 20/12/2013 Simulating grass weed (annual ryegrass) control WWBW CWWB FpWWB BmWWB BmCWB FpCWB Continuous cereal 1 Yr-Pea break 1 Yr-Canola break Pea-Canola break BM breaks Year 18 APSIM & LUSO James Hunt 18

19 Cumulative EBIT ($/ha) 20/12/2013 Simulating economic performance EBIT = Earnings before Interest and Tax 3500 BM breaks 3000 WWBW CWWB FpWWB BmWWB BmCWB Yr breaks Continuous cereal Year 19 APSIM & LUSO James Hunt 19

20 Real farm economic data Typical 1600 ha farm, real farm data Economic indicator Mixed Farm (67% Crop:33% Pas) Cont. Crop (Wheat-Canola) Cont. Crop (BM) (25% BM Pea) Trading Income $803,000 $900,100 $795,600 Oper. Costs Var. $362,600 $464,600 $361,100 Oper. Costs - Fixed $252,500 $258,500 $258,500 EBIT ($ pa) $187,900 $177,000 $176,000 Return on Assets 2.8% 2.6% 2.6% BM Pea-Wheat-Canola as profitable but with less production and financial risk

21 Case study 3 Millet cover crops in the north Q. Can they improve the water-balance for wheat crops? Skip-row sorghum low residue Wheat residue 21 21

Long-fallow in a typical northern crop sequence Year 1 Year 2 Year 3 Year 4 Year 5 Summer Sorghum Winter Fallow Summer Fallow Winter Wheat Summer Fallow Winter Chickpea Summer Fallow Winter Wheat

22 Long-fallow in a typical northern crop sequence Year 1 Year 2 Year 3 Year 4 Year 5 Summer Sorghum Winter Fallow Summer Fallow Winter Wheat Summer Fallow Winter Chickpea Summer Fallow Winter Wheat Summer Fallow Winter Fallow 14 month fallow between sorghum and wheat Millet cover crop? Low cover reduces infiltration and increases run-off Q1. Could a summer-grown millet cover crop improve the water balance? Q2. Would it use more water to grow than the cover conserves? Q3. When to sow? How long to grow? 22 22

23 31 field experiments and simulation... Cover crop Less runoff More yield Conv. Fallow Sow in September, remove at 50% cover (before December) Yield penalty in < 2% of years, and good erosion control Whish et al., (2009) Crop and Pasture Science, 60: Less soil loss More deep drainage 23 23

24 Conclusions re-evaluating cover crops Herbicide resistant weeds = a re-evaluation of cover crops Brown-manure legumes = weed, N and water benefits Limited medium to long-term experimental data Simulation suggest benefits, adoption is growing 24 24

25 Thank-you PLANT INDUSTRY/SUSTAINABLE AGRICULTURE 25

John Kirkegaard CSIRO Plant Industry, Canberra

Canola & its role in Australia s conservation farming revolution John Kirkegaard CSIRO Plant Industry, Canberra Why invite an Aussie? An oilseed (canola) is most important non-cereal crop (3 rd most important