Stubble management guidelines NUMBER for the Riverine Plains 03

Strategic in-crop management Key points supports success in stubble- No-till stubble-retained (NTSR) systems require strategic management to optimise crop retained systems nutrition, disease and yield potential. No-till stubble-retained (NTSR) Nitrogen management Nitrogen (N) availability during early cropping systems have demonstrated crop growth in NTSR systems can a wide range of benefits for growers Stubble retention is associated with a be impacted by nitrogen ‘tie-up’ as across the Riverine Plains region. temporary nitrogen lag during early crop microbes use soil nitrogen reserves to growth stages, as microbes ‘borrow’ soil fuel stubble breakdown. These include: improved soil moisture nitrogen to break down the stubble from retention during summer, protection from the previous crop — often referred to as Yellow leaf spot (YLS) control in wind and water erosion and increased nitrogen ‘tie-up’ (see boxed section on NTSR systems may be best achieved soil organic matter (SOM) levels, which all page 3). This may leave the current crop by applying fungicides during have positive impacts on soil structure and short on available nitrogen during the initial node development (GS31–33) to fertility. On the flipside, retaining stubble stages of plant growth if adequate fertiliser protect the major yield contributing can reduce nitrogen (N) availability during nitrogen is not supplied. leaves emerging from these growth early crop growth stages and increase stages onwards. the risk of stubble-borne diseases, such Work by Dr James Hunt and others at as yellow leaf spot (YLS), (particularly CSIRO suggests NTSR systems require an No yield benefits have been shown in second-year wheat crops sown with extra 5kg N/ha per tonne of canola or cereal over three years of trials using plant susceptible varieties). stubble at sowing in order to overcome any growth regulators (PGR), however, temporary nitrogen tie-up. As part of the PGRs did influence crop canopy In recent years, Riverine Plains Inc has GRDC investment Maintaining Profitable height and leaf orientation. carried out a number of trials as part of Farming Systems with Retained Stubble in the GRDC investment in the Improved the Riverine Plains Region project, field trials Normalised difference vegetation Water-Use Efficiency (WUE) in No-Till were sown at Daysdale/, New South index (NDVI) measurements correlate Cropping and Stubble-Retention Systems Wales and Yarrawonga, Victoria, during the well with crop dry matter (DM) and in Spatially and Temporally Variable 2014–17 seasons. These trials investigated nitrogen uptake data. This suggests Conditions in the Riverine Plains project. whether adding extra nitrogen at sowing it can be used to support in-crop These trials investigated a range of crop would compensate for this nitrogen tie-up nitrogen applications, however management strategies to support optimal effect and influence final crop biomass (dry appropriate ground-truthing is critical. production in NTSR systems. The results matter) or yield. from this project are described in the Riverine Plains Inc publication Between Daysdale/Corowa the Rows, which can be downloaded from: http://riverineplains.org.au. The Daysdale/Corowa trials have investigated the value of adding an extra 40kg N/ha at sowing where stubble had been cultivated just before sowing. This was to determine whether mixing the stubble into the soil increased the nitrogen requirement during plant establishment due to higher soil-stubble contact.

STRIVING TOWARDS SUSTAINABLE, PROFITABLE FARMING P1 NUMBER 03 Stubble management guidelines for the Riverine Plains

The dry matter (DM) results from 2015–17 sowing with cultivation over the NTSR demonstrated that adding nitrogen at control. In 2015 the burnt treatment sowing to cultivated stubble increased yielded less than the other treatments, crop DM through the season. However, which was most likely due to a heat stress for all years except 2017 (where the burnt event during October. In 2017, the NTSR treatment had significantly more biomass control out-yielded all other treatments. at harvest than the other treatments), any differences in DM between the Yarrawonga treatments had levelled out by harvest, Four years of trials at Yarrawonga from with all treatments supporting a similar 2014–17 investigated the value of adding final crop biomass. An example of results extra nitrogen at sowing to both cultivated is presented in Table 1, showing results and NTSR (standing stubble) treatments. from 2015. While there were some treatment effects on Four years of crop yield data (Figure 1) DM, there were no consistent increases in showed no increase in wheat yield when DM production due to extra nitrogen applied extra nitrogen was added at sowing to at sowing. Results from the 2017 trial are offset early nitrogen tie-up. Moreover, shown in Table 2. there was no difference in yield between Over the four years of the trial, there was the cultivated +40kg N/ha treatment and also no yield benefit in applying extra the NTSR (standing stubble) treatment, nitrogen at sowing, compared with the except in 2017 where the NTSR control NTSR control or the cultivated treatments, yielded significantly more than the other except in 2016, where the addition of treatments (Figure 1). nitrogen significantly increased the yield of Over the four years of research (2014–17) the cultivated treatment (Figure 2). Although at the focus farm there has been burning has increased DM production in all no consistent benefit to either cultivating, four years of trials, it was only in 2017 that it burning or adding additional nitrogen at generated a significant yield advantage over

TABLE 1 Dry matter at Daysdale/Corowa 15 July 2015, first node (GS31); 9 September Wheat growing through lightly incorporated stubble as part of the stubble management 2015, flag leaf fully emerged (GS39); 9 October 2015, mid-flowering (GS65) and 19 November, trials at Yarrawonga. harvest (GS99) Dry matter (t/ha) Treatment GS31 GS39 GS65 GS99 the NTSR treatments. This relates to high NTSR (control) 0.66a 3.81ab 6.94b 8.90a levels of stubble residue carried over with the NTSR treatments from 2016. Cultivated (one pass) 0.71a 3.47b 7.59b 9.12a Cultivated (one pass) + 40kg N/ha 0.70a 4.42a 8.01ab 8.77a While applying extra fertiliser at sowing to offset nitrogen tie-up may not always Burnt 0.73a 4.35a 9.34a 8.79a result in higher wheat yields for the Riverine Mean 0.70 4.01 7.97 8.90 Plains region, it may provide other benefits, LSD 0.18 0.69 1.45 1.89 such as increased early vigour. Early vigour Figures followed by different letters are regarded as statistically significant. may be of particular value if the winter turns wet and cold or if waterlogging becomes 6.0 a an issue. Such effects were observed in a 5.0 a a a the Yarrawonga region in the wet winter ab ab of 2015, where crops that received more 4.0 a b nitrogen up front were better established b b a b a a a and recovered more quickly from extended 3.0 waterlogging than those having less early- season nitrogen. Yield (t/ha) 2.0 2014 1.0 2015 Disease management 2016 0.0 2017 The carryover of stubble between seasons NTSR Cultivated Cultivated Burnt presents a disease challenge in many (control) (one pass) (one pass) + 40kg N/ha NTSR systems. While there are several Stubble managment diseases of importance in cereal crop production systems, yellow leaf spot (YLS) FIGURE 1 Yield data from time replicate trials 1, 2,3 and 4 — the Daysdale (red brown earth), (Pyrenophora tritici repentis), is of particular Corowa (heavy grey clay), Coreen (loam over clay) and Coreen (loam over clay) trials for 2014, interest to wheat growers in the Riverine 2015, 2016 and 2017 — cv Whistler (wheat) in 2014, cv Mace (wheat) in 2015, cv Hindmarsh Plains region because it survives on stubble (barley) in 2016, cv Scepter (wheat) in 2017 between seasons. Yield bars for the same year (same colour) with different letters are regarded as statistically different. Note: The four trials were carried out on the same farm but not on the same trial site. During 2014 the cultivation treatments were established with two passes of a multidisc, while in 2015, 2016 and 2017 a single pass was used.

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Nitrogen tie-up TABLE 2 Dry matter at Yarrawonga 19 July 2017, start of stem elongation (GS30); 5 September explained 2017, flag leaf fully emerged (GS39); 13 October 2017, watery ripe grain (GS71) and 23 November, physiological maturity (GS95) NTSR — long stubble (control) NTSR — long stubble + 40kg N/ha NTSR — short stubble Straw removed Dry matter (t/ha) 1. Soil naturally contains carbon (C) and Cultivated (one pass) Cultivated (one pass) + 40kg N/ha Burnt nitrogen (N), with soil organic matter (SOM) Treatment0.9 GS30 GS39 GS71 GS95 having a C:N ratio of about 10:1. This ratio b c b b NTSR0.85 — long stubble (control) 0.82 2.57 6.62 7.80 is optimum for microbial function. Wheat NTSR — long stubble + 40kg N/ha 0.82b 3.01b 6.72b 7.69bc stubble contains lots of carbon and only a 0.8 NTSR — short stubble 0.96a 2.88bc 6.86b 8.04b little nitrogen; with a C:N ratio of at least 0.75 ab b b b 80:1. Straw0.7 removed 0.88 3.01 6.78 8.03 ab bc b c Cultivated0.65 (one pass) 0.88 2.94 6.59 7.16 ab bc b bc

NDVI (scale 0–1) Cultivated (one pass) + 40kg N/ha 0.89 2.76 6.65 7.43 C C C C 0.6 C N C Burnt 0.98a 3.65a 7.44a 8.97a C C N C N 0.55 Mean 0.89 2.98 6.81 7.87 N C C 0.5 N GS32 GS45 GS71 C N C N N LSD 0.12 0.43 0.45 0.62 N N N Figures followed by differentAssessment letters are regarded timing as statistically significant.

2. When the autumn break comes and microbial activity fires up, the soil microbes 2014 2015 2016 2017 start breaking down carbon in the stubble 8

and converting it to SOM. The microbes use 7 a some of the soil nitrogen reserves as ‘fuel’ ab abc 6 bc bc bc to undertake this process. c 5 a a a a a a a 4 ab ab b b a b C C ab ab ab b C Yield (t/ha) C 3 b b b C N C N C C N C 2 N C C 1 C N C N N N N 0 N N NTSR NTSR long Straw Cultivated Cultivated Burnt NTSR long stubble + 40kg N/ha removed (one pass) (one pass) short stubble (control) + 40kg N/ha 3. A young plant growing in a stubble-retained Stubble treatment system might not have much nitrogen available as the microbes have borrowed it FIGURE 2 Yield data from the four Yarrawonga trials for 2014, 2015 (cv Young), 2016 and 2017 to break down stubble. This is why young (cv Corack) plants in wheat stubble may show nitrogen Note:120 The NTSR — short stubble was not part of the 2014 list of treatments. Yield bars across treatments for the same year (same colour) with different106.3 letters are regarded106.0 as statistically deficiency or have less vigour. 100 103.2 101.5 100.7 101.0 different.100

80

60

N C C 40 C C N N 20

% Yield four-year mean (2014–17) 0 4. As the stubble breaks down, the microbes NTSR NTSR long Straw Cultivated Cultivated Burnt NTSR long stubble + 40kg N/ha removed (one pass) (one pass) short stubble return nitrogen to the soil reserves. This (control) + 40kg N/ha extra nitrogen provides a boost for plant Stubble management prior to second wheat growth. Nitrogen tie-up in the early growth (100 = 4.14t/ha) stages doesn’t always correlate to a yield penalty, as the plant compensates by 2014 2015 2016 2017 7 building biomass later in the season. a a a a a a 6 a a a b 5 a N N N 4 a a a a N 3 a a a a Yield (t/ha) a N N C 2 C C Yellow leaf spot (YLS) (Pyrenophora tritici N N N repentis). Photo courtesy: Evan Collis. N N N 1

0 NTSR NTSR CultivatedSTRIVING TOWARDSStraw SUSTAINABLE, removed PROFITABLEBurnt FARMING P3 (short stubble) (long stubble) (one pass) Stubble treatment NUMBER 03 Stubble management guidelines for the Riverine Plains

The control of YLS through different TABLE 3 Yield of treatments for the control of YLS, with nitrogen and fungicide applications fungicide and nitrogen application strategies targeted for tillering (GS22–25) and first node (GS31–33), 2013–16 has been evaluated through the GRDC- Grain yield (t/ha) funded Maintaining Profitable Farming Systems with Retained Stubble in the Yarrawonga, Coreen, Corowa, Yarrawonga, Victoria NSW NSW Victoria Riverine Plains Region Project (2013–18). Treatment 2013 2014 2015 2016* Four years of field trials (2013–16) were carried out to determine the value of Target nitrogen timing using fungicides (product and timing of GS22 2.71a 3.81a 3.78a application) and nitrogen to control YLS in GS31 2.70a 3.64a 3.26b early-sown second wheat crops. LSD 0.04 0.19 0.18 For three successive years a response to foliar fungicides for YLS control was Target fungicide timing observed. This was despite yields being Untreated control 1.79b 2.58c 3.57b 3.42a less than 4t/ha during 2015 and less GS23–25 1.88b 2.72b 3.62b 3.52a than 3t/ha the previous two seasons, with disease levels being relatively low GS32–33 1.89b 2.71b 3.97a 3.55a (less than 20% on the top three leaves) GS23–25 and GS32–33 2.06a 2.81a 3.74ab 3.59a (Table 3). In 2016, despite the high incidence of YLS throughout the season, LSD 0.15 0.07 0.26 0.25 there was no significant yield response Product to fungicide due to the effect of severe Prosaro 1.96a 2.73a 3.65a 3.54a waterlogging on the trial. Tilt 1.85a 2.67b 3.8a 3.5a Over the four years of this trial the key messages are: LSD 0.77 0.03 0.19 0.18 • Timing of nitrogen application did Mean 1.91 2.70 3.73 3.52 not influence yield when applied in * As a result of the wet conditions experienced during winter 2016, nitrogen and fungicide applications targeted for conjunction with fungicide during 2014 GS22-25 and GS32-33 were delayed until GS31 and GS33 respectively and 2015. When nitrogen timing was Figures followed by different letters are regarded as statistically significant. delayed until third node (GS33) in 2016, yield was significantly reduced compared with the first node (GS31) timing. • A single fungicide application for YLS at late tillering is of limited value, with greater control and yield benefit from a later fungicide application • During 2013 and 2014 a two-spray fungicide program achieved the best YLS control. • During 2014 Prosaro® performed better than Tilt®, with no difference between the two products in 2013, 2015 or 2016. Varietal susceptibility, disease pressure, environmental factors and fungicide choice all play a role in determining the value of fungicide application for YLS control. As a general rule, the use of fungicides for YLS early in the season may not be economic, however in a wet spring there may be benefit in protecting the top leaves from disease. The use of resistant varieties and rotations that include break crops such as canola and pulses, will also aid in managing YLS. While barley doesn’t display symptoms of YLS, barley stubble can host the disease and provide a source of infection for the following crop.

Large plot stubble management trials, Yarrawonga.

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What is NDVI and how is it measured?

Normalised Difference Vegetation crop greenness at a specified point, or Index (NDVI) is a measure of the across a paddock if GPS referenced. amount of live green vegetation, or This can be used through the vegetative the greenness of a crop canopy. stage to assess nutrition status, and determine the requirement for Live green plants absorb visible extra nitrogen. light (solar radiation) as part of photosynthesis. At the same time, plants NDVI maps can also be accessed reflect solar energy in the near infra- from satellite data, which comes from red range. instruments on board the National Oceanic and Atmospheric Administration Measuring the difference between the (NOAA) series of satellites operated visible and near infra-red light above by the United States. Paddock-scale a plant canopy provides a measure of NDVI maps, taken at specific time greenness, which is converted to an points, can be purchased and used for index of between -1 and +1. Values both in-season fertiliser decisions, and are commonly between 0.1 and 0.7 for providing additional spatial data to with higher values associated with interpret variability shown by yield maps. greater density and greenness of the plant canopy. Source of NDVI information: Australian Government, Bureau of Meteorology 2016. NDVI decreases as leaves come under water stress, become diseased or die. Two ways of measuring NDVI NDVI image collected as part of paddock-scale NDVI can be measured in-crop using experiments conducted within the Riverine Plains a handheld device (e.g. GreenSeeker), Inc Stubble Project, August 2016. Copyright which provides a numerical value on Precision Agriculture.

Sowing varieties within their recommended compared to the untreated control. This Applying a PGR did not affect yield in sowing window and supplying adequate suggests crop biomass was redistributed, any of the trials, and did not interact with nutrition ensures crop development occurs not decreased. additional nitrogen applied above the at the appropriate time and that plants standard farm application rate. This was NDVI readings (see boxed section) taken are vigorous. Healthy, vigorous crops shown at a representative trial at Dookie with a handheld GreenSeeker® were lower are better able to resist or outgrow the during 2015, where nitrogen was applied with PGR application. This suggests the effects of disease, limiting the potential for above the farm standard of 142kg N/ha PGR either altered the greenness of the yield losses. Choosing a variety with YLS (Figure 3). crop canopy, or changed the orientation of resistance and burning infected stubble will the leaves, making them more upright (and also help reduce the inoculum source. so producing less reflectance). Plant growth regulators in stubble- retained systems Yield (t/ha) Protein (%) Plant growth regulators (PGRs) are routine 5.00 18.0 inputs for high-yielding cereal crops grown elsewhere in the world to shorten the crop, 4.00 17.0 prevent crop lodging and avoid associated yield penalties. 3.00 16.0 Six trials were carried out across four years 2.00 15.0 Yield (t/ha) in the Riverine Plains region (2013–16) Protein (%) to determine if the larger crop canopies 1.00 14.0 associated with early sowing, higher rates 0.00 13.0 of nitrogen, or both, would benefit from Std N Std N Std N Std N Std N Std N PGR application. (as farm) + 40N + 80N (as farm) + 40N + 80N No PGR Plus PGR During the four years of trials, it was found Nitrogen and PGR application that applying a PGR (Chlormequat + Moddus®) decreased crop height by up to FIGURE 3 Influence of nitrogen application and PGR application on yield and protein at 8cm without influencing DM except in 2016, Dookie, 2015 where harvest DM was significantly lower The error bars are a measure of LSD.

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Using in-crop NDVI to measure results are presented as an average across nitrogen requirements both timings. Trials carried out as part of the GRDC- As seen in Figure 4, additional nitrogen funded Maintaining Profitable Farming fertiliser increased the NDVI readings, Systems with Retained Stubble in the with the greatest difference seen in NDVI Riverine Plains Region Project (2013–18) values at the start of ear emergence measured in-crop NDVI through the (GS51) and mid-flowering (GS65). As season to determine the responsiveness shown in Table 4, the differences in NDVI of wheat crops to nitrogen applications. measured in the field at GS51 and GS65 The trial results from the 2014 Dookie site with a GreenSeeker correspond well demonstrate how NDVI values correlate to differences in DM, nitrogen uptake with other measurements (Figure 4). and yield. The Dookie trial evaluated three rates of While trial work is continuing to refine nitrogen application, (0, 60kg N/ha, 120kg the relationships between NDVI and N/ha), with the fertiliser either applied all at different growth parameters, results to first node (GS31) or split between the first date suggest an increase in NDVI up to fully-unfolded leaf (GS11) and first node mid-flowering may correlate with greater (GS31) stages. As there was little difference biomass and yield potential. between the two nitrogen timings, the NDVI Acknowledgements

g ha g ha g ha Thank you to our project partner FAR Australia for managing the field operations for the stubble management trials. Thanks also to our farmer cooperators, Tomlinson Ag at Coreen, Telewonga Pty Ltd at Yarrawonga, Ludeman Brothers at Dookie, and Mr

NDVI Peter Campbell at Henty. This stubble management guideline has been developed for Riverine Plains Inc as part of the Grains Research and Development Corporation investment in the Maintaining Profitable Farming Growth stage Systems with Retained Stubble in the Riverine Plains Region project (GRDC FIGURE 4 Influence of applied nitrogen rate on NDVI scale 0–1* at Dookie, 2014 RPI00009). * The error bars are a measure of LSD. The Stubble Initiative involves farming systems groups in Victoria, South TABLE 4 A comparison of different growth parameters measured 11 September 2014 at Australia and southern and central , collaborating with Dookie, start of ear emergence (GS51) and 3 October 2014, mid-flowering (GS65) research organisations and agribusiness, Nitrogen to address challenges associated with Measurement timing, DM uptake NDVI scale Yield stubble retention. nitrogen rate (t/ha) (kg N/ha) (0–1) (t/ha) The GRDC, on behalf of growers and GS51 the Australian Government, is investing 0kg N/ha 5.63b 66c 0.58c 4.83b $17.5 million in the initiative that has been instigated by the GRDC Southern 60kg N/ha 6.65a 111b 0.71b 5.97a Regional Panel and the four Regional 120kg N/ha 6.41a 130a 0.78a 6.17a Cropping Solutions Networks that GS65 support the panel. 0kg N/ha 8.15c 57b 0.57b 60kg N/ha 10.10b 100a 0.69a 120kg N/ha 11.31a 113a 0.74a The yield is recorded for the three nitrogen rates applied Published June 2018 Farmers inspiring farmers

DISCLAIMER | Any recommendations, suggestions or opinions contained in this publication do not necessarily represent the policy or views of the Riverine Plains Inc or the Grains Research and Development Corporation (GRDC). No person should act on the basis Riverine Plains Inc. of the contents of this publication without first obtaining specific, independent professional advice. The Riverine Plains Inc, GRDC PO Box 214 NSW 2647 and contributors to these guidelines may identify products by proprietary or trade names to help readers identify particular types of products. We do not endorse or recommend the products of any manufacturer referred to. T. (03) 5744 1713 Other products may perform as well as or better than those specifically referred to. The Riverine Plains Inc and GRDC will not be liable E. [email protected] for any loss, damage, cost or expense incurred or arising by reason of any person using or relying on the information in this publication. W. riverineplains.org.au