Grazing oilseed brassicas an economic and agronomic evaluation for Australian conditions

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1 Grazing oilseed brassicas an economic and agronomic evaluation for Australian conditions John Kirkegaard 1, Susan Sprague 1, Steve Marcroft 2, Hugh Dove 1, Chris Duff 3 1 CSIRO Plant Industry, GPO Box 1600, Canberra ACT 2601, Australia john.kirkegaard@csiro.au 2 Marcroft Grains Pathology, 110 Natimuk Rd., Horsham, VIC. 3400, Austrailia 3 Delta Agribusiness, 287 Boorowa St, Young, NSW 2594, Australia ABSTRACT The term dual-purpose canola describes the use of a canola crop for forage prior to seed production, in the same way as for dual-purpose cereals. We investigated the feasibility of utilising canola in this way in a pilot study near Canberra from 2004 to 2006, and conducted a risk and opportunity survey among industry specialists to consider the broader potential across Australia in Current research, including varietal evaluation and on-farm testing is providing further insights into the agronomic and economic potential of the concept. In the pilot study near Canberra, European winter and mid-late maturing Australian spring canola varieties sown from early March to mid-april produced 2.5 to 5.0 t/ha of biomass in winter providing up to 3.5 t/ha of high quality forage. The forage was highly digestible and Merino hoggets grew at 210 g/day from DM intake of 1531 g DM/day. Delays in flowering associated with grazing ranged from 0-4 days when grazed before buds were visible to 28 days if the crop had commenced flowering. Delays in flowering of up to 14 days did not reduce seed yield or oil content when favourable spring conditions allowed compensatory growth. Yield loss occurred in poor springs or if grazing continued too late into spring, but the yield loss could be offset by the value of the grazed forage. The mean gross margin for dual-purpose canola ranged from $550 to $802/ha compared to $304/ha for grain-only canola. An assessment of the potential whole-farm impact of grazing canola on a 1300 ha mixed farm in the Young district of southern NSW suggests it could increase farm profit by $10,000 to $20,000 per year. Many additional system benefits including control of herbicide-resistant weeds were difficult to quantify. In the Industry survey, potential applications were suggested in all current canola growing areas as well as new areas in the high rainfall zone (including WA). In all cases, dual-purpose use relies on early sowing opportunities, varieties with the correct phenological fit, and careful grazing management to balance any trade-offs between the value of the forage and that of the seed. The impacts of early sowing and defoliation by grazing on disease interactions including blackleg, are important considerations under investigation. Key words: feed gap, mixed farming, Brassica, grazing INTRODUCTION Dual-purpose cereals have been an integral component of mixed farming operations in the medium to high rainfall zones of southern Australia for some time, and the area of milling quality, dual-purpose wheat has expanded rapidly since 2000 (Virgona et al. 2006). Semi- or obligate-winter cereals sown early in autumn produce forage during the winter feed-gap as the vernalisation requirement delays floral initiation and stem elongation until after winter grazing has ceased. Early-sown winter wheat can be exposed to a higher risk of leaf and root diseases which host on recently removed pasture grasses and volunteer cereals, and the recent outbreak of wheat streak mosaic virus has reduced the area significantly. Dualpurpose oat and triticale crops are less affected by disease but produce a lower value grain. A dual-purpose, broadleaf crop with a high grain value such as canola (Brassica napus) would provide an excellent break crop for weed and disease control and increase the flexibility and profitability of mixed farming operations. The possibility of utilising later-maturing spring or winter canola varieties sown earlier than normal to produce winter forage for grazing and to subsequently harvest for oil has not been previously investigated in Australia. We discuss the outcomes of field experiments in southern NSW and an industry risk and opportunity assessment to consider the agronomic and economic potential of dual-purpose canola in Australia.

2 MATERIALS AND METHODS A. Canberra Pilot Study. A series of experiments was conducted at Ginninderra Experiment Station (GES) near Canberra, Australia from 2004 to 2006 (Table 1). In experiments 1 to 3, the focus was on measuring early forage production and the impact of grazing at different times on re-growth, seed yield and oil content. Australian mid-late maturing spring varieties and French winter varieties all with good blackleg resistance were included. Sowing dates, varieties and the time of grazing were varied in each experiment. The plots were crashgrazed with large numbers of sheep over relatively short periods using exclosures to provide un-grazed areas for comparison. Details of the experimental design and agronomic management can be found in Kirkegaard et al. (2006, 2007). In experiment 4, larger replicated areas of canola (4 x ha) were grazed under more realistic stocking rates (32.7 dse/ha for 24 days) to assess the value of forage for animal production. Diet composition and intake measurements were measured using both direct forage sampling in grazed and ungrazed areas before and after grazing, and by using analysis of the cuticular wax alkane profiles in the herbage and faecal samples during grazing (Dove and Mayes 2006; Lieschke 2006). Liveweight gains were calculated by weighing animals before and after grazing. Gross margins for grain-only and dual-purpose canola were calculated for the variety Maxol in all experiments by valuing the canola forage based on either agistment rates ($0.50/sheep/week=$80/t) or using feed conversion rates measured in experiment 4 and a price of $1.65/kg for liveweight gain. Fixed production costs ($350/ha) and prices for canola seed ($325-$400) reflected commercial reality for the period. Table 1. Summary of experiments conducted at Ginninderra Experiment Station, Canberra ACT between 2004 and Varieties shown in italics are Australian spring varieties. Exp. Year Sowing Treatments Harvest Varieties Grazing April Hyola60, Maxol, Capitol Aug 26 Nov 16 Dec April Maxol, Capitol, Columbus 5 13 Sept 1 15 Dec March Thunder, Maxol, Capitol 3 5 May 6 22 Nov Columbus and/or Aug April Maxol 4 28 Sept Nov B. Risk and opportunity assessment. We consulted widely among growers, consultants, breeders, agronomists, other scientists and industry specialists across southern and western Australia during 2006, as well as scientists in USA, Canada, Europe and South Africa. In all we conducted 25 group consultations or presentations across southern Australia and published 15 articles in various industry forums. In response to the pilot study outcomes, we sought expert views on the potential areas and farming systems for adoption, varietal selection, and the critical threats and constraints to adoption of the concept. We used outcomes of these consultations together with some preliminary climatic risk assessment using the MetAccess climatic database software to evaluate agronomic and economic potential of dual-purpose canola across Australia and to guide further research. C. Whole-farm economic benefits a case study. We conducted a case study using real farm-based economic data from consultants near Young and Wagga in southern NSW to scale up the pilot study outcomes and estimate the likely whole-farm benefits of grazing canola. A typical 1300 ha mixed farming business with a 50/50 crop-pasture mix was used in the case study. We considered the way in which dual-purpose canola would be likely to be integrated into the farm. Typical gross margins for commercial farming enterprises and those determined for dual-purpose canola in the Canberra pilot study were used. The major benefits of the grazing canola to the business could be quantified relatively simply as increases in gross margins because the fixed costs of the farming operation would not be altered by incorporating grazing canola into the system. However significant system benefits such as the improved ability to control herbicide resistant ryegrass, improved pasture re-growth as a result of spelling afforded by the grazed crop, and the potential disease break effects for cereals were obvious and important but more difficult to quantify.

3 RESULTS A. Canberra Pilot Study. The years 2004 to 2006 experienced dry autumn conditions well below the long-term average for GES and irrigation was required to establish the experiments. Growing-season rainfall (sowing to windrow) was close to long-term average (400mm) in 2004 (330mm) well above average in 2005 (610mm) and below average in 2006 (258mm) when irrigation (60mm) in September and October was required to avoid crop failure (experiment 4 unirrigated). A frost (-2 o C) on 26 th September 2006 caused some pod loss, and a period of hot weather (32 o C) around 14 th October 2006 caused premature cessation of flowering. Biomass production. Winter types sown in early March (experiment 3) produced 2.5 to 3.5 t/ha of biomass within 8 weeks, providing up to 1 t/ha of high-quality forage for grazing by early May (Table 2). The Australian spring variety produced comparable biomass but the early onset of flowering made it less suited to early sowing. The winter and long-season spring varieties sown in mid-april produced 2.5 to 5.0 t/ha of biomass in winter providing 0.3 to 3.5 t/ha of high quality forage for grazing by mid-august (Table 2 shows data for cv. Maxol only) Grazing by sheep. The sheep readily ate canola forage from early vegetative to flowering and early pod stage and showed no preference for a commercial fodder hybrid brassica when offered a choice. The canola forage was highly digestible and in experiment 4, Merino hoggets grew at 210 g/day from a DM intake of 1531 g DM/day. Impact of grazing on canola growth and development. Grazing delayed flowering and reduced plant height depending on the intensity of grazing and the plant stage at the time of grazing. The delays in flowering were 0-3 days if grazing occurred before buds were visible, 4 days if buds were visible but not elongated, 7 to 15 days if buds were elongated 25 cm but no flowers were open, and 25 to 30 days if plants were in flower. Impacts of grazing on yield. Yield impacts of grazing depended on both the magnitude of the growth and development changes (above) and on the seasonal conditions during the recovery period. In experiment 1 (2004) there was no yield penalty for winter and late-spring types grazed in mid-august due to a favourable spring finish (Table 2). In 2005, a yield penalty of 0.5 t/ha was incurred due to the late grazing (mid-september) which left insufficient time for recovery despite ideal spring conditions. In 2006, winter types showed no yield penalty from mid-august grazing at bud visible (Table 2), while the spring types which were flowering when grazed did not recover (data not shown). Winter types grazed later (experiment 4) also did not recover to produce seed in the 2006 drought (Table 2). Gross margin analysis. Canola forage provided a direct increase in gross margin where yield was unaffected by grazing (experiments 1, 3). The yield loss was more than offset by the value of the grazed forage (experiment 2), particularly in drought years where significant financial losses were minimised (experiment 4). Hay or silage production would have been a further option. Table 2. Gross margin for grain only or dual-purpose canola (cv Maxol) in experiments conducted at Ginninderra Experiment Station 2004 to Year Crop option Forage (t/ha) Grain (t/ha) Oil (%) Gross margin ($/ha) Grain only (Exp 1) Dual-purpose Grain only (Exp2) Dual-purpose Grain only (Exp 3) Dual-purpose Grain only (Exp 4) Dual-purpose Mean Grain only Dual-purpose A Forage was valued conservatively using agistment rates of $0.50/sheep/week (equivalent to $80/t) or using feed conversion for a sheep meat enterprise (equivalent to $189/t). Grain was valued at $325/t in 2004/05 and $400/t in 2006 and fixed production costs were $350/ha. Cost and price estimates for individual enterprises should be applied according to specific circumstances.

4 B. Risk and opportunity assessment. The consultation among industry specialists suggested that the potential applications of dual-purpose canola extended beyond the high-rainfall zone of southern NSW where the pilot study had been conducted, and identified a number of key issues related to successful development of the idea. Potential areas and farming systems for adoption. Applications were suggested in all current canola growing areas as well as new areas in the high-rainfall zone (including WA), but three general scenarios emerged: (1) Grazing winter canola Targeted at the cooler, high-rainfall Tablelands and slopes where dual-purpose cereals are currently grown. (2) Grain-graze trade-off A majority of people believed that early March sowing opportunities would be relatively infrequent and where they occurred, good pasture growth may offset the need for additional forage. A more likely scenario in the medium- to high-rainfall zones where canola is currently grown would be to sow late March to late April, 2 to 4 weeks earlier than normal using long-season spring varieties or hybrids, and utilise grazing to delay flowering back into the usual window so that pod-filling occurs at the usual time. In higher-rainfall areas, longer cool springs may accommodate later flowering and reduce the trade-off with yield. As many farms are mixed crop/livestock enterprises, yield reductions can be offset by the value of the grazed forage. Potential areas include Western District and NE Victoria, Southeast SA, southern NSW and high rainfall zones of WA. (3) Clip grazing On larger crop-focussed farms in traditional canola growing areas, less intensive clip-grazing of crops sown on time using fewer sheep on larger paddocks may be possible and has been used with some success in southern NSW. Grazing is managed to minimise any delay in flowering as seed yield is the main profit driver on these farms. Varietal choice. Important varietal characteristics were: (1) high and robust blackleg resistance (2) vigorous early forage production for grazing, (3) high-quality forage with low risk of animal health issues (4) ability to tolerate and recover from grazing (5) option to produce hay or silage in dry finish (6) high yield and oil after grazing. Depending on the strategy for specific farming systems a wide range of conventional, TT, hybrid, winter/spring or winter varieties may adequately meet these requirements. Critical threats and constraints. The major threats were: (1) the potential disease and pest implications of early sowing and winter defoliation (2) successful early sowing opportunities (3) impacts of delayed flowering on yield. Other important but manageable issues were (4) chemical withholding periods for grazing and (5) grazing management including animal health issues. Of the pests and diseases the implications for blackleg are potentially the most critical, as the impact of exposing damaged stems and petioles directly to blackleg spore showers in the winter is unknown. The early sowing opportunities relate to the probability of sufficient rainfall to allow successful establishment of the crop, and adequate preparation of the paddocks to ensure success. We used the MetAccess climatic data base software to investigate the probability of receiving a sowing opportunity (a total of 25 mm over 5 days) in various sites in south-eastern Australia (Table 3). These estimates provide a guide to likely potential areas and frequency of adoption, but depend on relatively simple rules. Consultants in southern NSW consider the estimates conservative and believe that with adequate preparation, sowing opportunities in March occur in 60% or even 80% of seasons (based on experience with dual-purpose cereals).

5 Table 3. Time of year when chance of sowing rain is 33 or 50%, and when chance of high temperature stress exceeds 10% or 20% at selected sites in southern Australia. Probability NSW/ACT VIC/SA Canberra Wagga Condobolin Hamilton Naracoorte Horsham Sowing opportunity (25 mm over 5 days) 33% 20 March 24 March 29 March 7 April 8 April 18 April 50% 5 April 13 April 25 April 24 April 23 April 2 May Heat stress (chance of > 29 o C) > 10% 12 Nov 18 Oct 24 Sept 12 Nov 22 Oct 24 Oct > 20% >30 Nov 12 Nov 18 Oct >30 Nov >30 Nov 12 Nov C. Whole farm economic benefits a case study. The enterprise considered in the study was a typical 1300 ha mixed farming enterprise near Young in southern NSW where dual-purpose cereals have been part of the system for some time. On-farm agronomic and economic data derive from clients of DeltaAgribusiness over the seasons 2000 to On mixed farms, the profitability of the grazing enterprise is determined largely by the winter stocking rate. Dualpurpose crops accumulate more biomass and can carry more stock than pastures during these winter months, and grazing the crops provides a period to allow the pastures to recover, together reducing the risk of costly supplementary feeding. The dual-purpose crops are also a risk management tool securing income from dry matter when rainfall is good and providing flexibility to produce hay, silage or trade livestock on spared pasture if the spring season is good. In the scenario below (Table 4) we have integrated grazing canola into the farm enterprise by replacing 50 ha of the lower value dual-purpose oats with 50 ha of the higher value dualpurpose canola, and by replacing 50 ha of grain-only canola with 50 ha of dual-purpose canola. In the case of the oats we have assumed that the grazing value of oat and canola is similar and the increased gross margin ($180/ha) derives from the higher value canola grain ($240/ha GM for oats vs $440 for canola). This represents a potential $9,000 increase in farm profits in years where this can be achieved. Table 4. An example of the potential change in enterprise area for a 1300 ha mixed farm near Young in southern NSW following integration of dual-purpose canola. Enterprise Current (ha) New (ha) Pasture Grain-only wheat Grain-only canola Dual-purpose wheat Dual-purpose oat 50 0 Dual-purpose triticale Dual-purpose canola Total grazed crop Total grazed area Winter dse/ha To determine the likely impact of dual-purpose canola replacing grain-only canola we combined information from the Canberra pilot study, and also experience from adoption of dual-purpose cereals, as our current data suggest that the amount and quality of forage produced by canola is similar to wheat. Typically the economic benefit of dual-purpose cereals over grain-only cereals in southern NSW has been around $100/ha when the feed is valued at agistment rates (Holmes and Sacket (2006); Duff and Condon (2007)) but $300 to $400 when the feed is valued from various animal meat enterprises (e.g. trading cattle, prime lambs). This range is similar to the benefits of dual-purpose canola (Table 2). For the 50 ha conversion this represents an increase of $5,000 to $18,000 in farm profits. Together, these two changes represent a potential $14,000 to $27,000 increase in years where grazing canola

6 can be adopted. Assuming that this is 2/3 of years (based on experience with grazing cereals) this represents a mean potential gain in farm profit of $10,000 to $20,000 depending on the type of animal enterprise. Based on average farm profits of $200,000 for mixed farms in the area (Holmes and Sackett 2006) this is a 5-10% increase in average farm profits. Other obvious but difficult to quantify system benefits of a dual-purpose canola are improved ability to control herbicide-resistant ryegrass, improved pasture re-growth as a result of spelling afforded by the grazed crop, and the potential disease break effects for subsequent cereals. At present the loss of dual-purpose wheat due to wheat streak mosaic virus (not considered above) provides further opportunity for higher value dual-purpose canola to fill the gap. These types of economic analysis will be specific to each region and sensitive to assumptions about the frequency and area of dual-purpose crops which can be grown. DISCUSSION The pilot study conducted in Canberra resolved a number of questions regarding the potential to use canola as a dual-purpose crop. The work demonstrated that canola could produce significant amounts of high-quality winter feed which was readily eaten by sheep, was of high quality in terms of animal liveweight gains, and that the canola could recover with little or no impact on seed yield and quality when grazing was managed well. The preliminary varietal comparisons conducted within the study demonstrated clear interactions between the phenology of the variety, and management factors including the sowing date, grazing time and duration, to balance forage production and seed yield. These interactions will be specific to different regions within Australia, but the industry consultation to date suggests significant potential to utilise dual-purpose canola in other regions within Australia. Identifying varieties with the correct phenology for different regions is a key focus of current research. Genotypic variability in early biomass production, forage quality, re-growth after grazing and disease susceptibility are also areas of current research. Two important agronomic considerations common to all applications of the concept are the ability to successfully establish canola earlier than usual, and the impact of early sowing and grazing on pest and disease interactions. Analysis of climatic data (e.g. using MetAccess) and experience can go some way to indicating the chances of early sowing, but consultants in southern NSW argue that good managers who prepare well are able to capitalise on early sowing opportunities much more frequently than would be anticipated. Prior weed and stubble management combined with suitable machinery and timeliness can increase the chances of success. A focus on successful early establishment of canola, often into cereal stubbles will be needed. Realistic assessments of the timing and frequency of early sowing are crucial to any predictions on the total area of adoption. Refining other agronomic aspects such as sowing rates, row configuration and fertiliser management may also provide further benefits. The impact of early sowing and grazing on pests and diseases, particularly blackleg, need to be resolved before dual-purpose canola can be adopted with confidence. Damaged stem and leaf petioles exposed to blackleg spore showers during winter may increase infection although the susceptibility of different forms of blackleg resistance to this type of infection process is uncertain. In the Canberra pilot study, blackleg levels were too low to resolve this issue but there was evidence of increased blackleg infection severity under grazing. Several experimental field sites in 2007 are heavily infected with blackleg and will provide an excellent opportunity to assess this issue. A range of other potential pests and diseases of early-sown crops were identified as were issues of agri-chemical withholding periods, but these were considered to be resolvable at present. Our preliminary economic analysis of dual-purpose canola in southern NSW suggests that significant direct and indirect benefits to the farming system are possible. Our assumptions may be contestable, and we acknowledge that further assessment of the impact of climatic variability on the performance of dual-purpose canola is necessary as evidenced by the large variation in the gross margins measured in the Canberra pilot study. Expert opinion and current field experiments will be supplemented by simulation analysis to examine this profit

7 variability, although some system benefits are difficult to capture in simulation models. Early sowing opportunities and biomass production can be adequately simulated, but there are currently few data sets available to simulate the impact of grazing on canola re-growth and yield. At present our approach is to proceed with varietal evaluation in different regions identified in the survey, with field testing under commercial mixed farming conditions with informed grower and consultant groups, and with compilation of agronomic data sets to assist in simulation studies to extrapolate across a wider range of regions and seasons. We remain confident that there is considerable scope to capture value from grazing early-sown canola crops during winter without significant uneconomic trade-offs with seed yield. ACKNOWLEDGEMENTS The authors thank staff at CSIRO Ginninderra Experiment Station for assistance in managing the crops and livestock in these experiments and the technical assistance of Mr John Graham, Mr Geoff Howe and Mr Mark Smith. We also thank the many canola industry experts consulted during the course of the risk and opportunity analysis and Mr Tim Condon, DeltaAgribusiness Harden, NSW for discussion on the farm case study. REFERENCES Dove, H. and R.W. Mayes, 2006: Protocol for the analysis of n-alkanes and other plant-wax compounds and for their use as markers for quantifying the nutrient supply of large mammalian herbivores. Nature Protocols 1, (At Duff, C, and T, Condon, 2007: Crop variety and management Update DeltaAgribusiness, Young NSW Australia. Holmes, P. and D. Sackett, 2007: Aginsights 2006 knowing the past: shaping the future. Holmes Sackett and Associates, Wagga Wagga NSW Australia. Kirkegaard, J.A., S.J. Sprague, H. Dove, W. Kelman, S.J. Marcroft 2006: Dual-purpose canola a new opportunity in mixed farming systems? Proc. 13 th Aust. Soc. Agronomy Conf., Perth Western Australia. Kirkegaard, J.A., S.J. Sprague, H. Dove, W.M. Kelman, S.J. Marcroft, A. Lieschke, 2007: Dual-purpose canola a new opportunity in mixed farming systems. Aust. J. Agric. Res. (in review). Lieschke, A.L., Validation of the n-alkane procedure for the estimation of diet composition and intake of sheep consuming chicory; and intake and diet composition data of sheep grazing dual purpose canola. B. App. Sci. (Hons) thesis, Charles Sturt University, Wagga Wagga, Australia. Virgona J.M., F.A.J. Gummer, J.F. Angus, 2006:. Effects of grazing on wheat growth, yield, development, water use and nitrogen use. Aust. J. Agric. Res. 57,

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