Key agronomic practices and management to maximise profits from dual-purpose crops

Take home messages

• Dual-purpose (DP) crops can increase farm profit across a range of environments. Learnings from experiences in southern NSW are presented as examples.
• Higher whole-farm profit relies on attention to detail with crop and livestock management.  Establishing the right crop early and correct lock-up time are key to increasing profit and reducing risk.
• Lock-up time is the critical decision to maximise profit. The time of lock-up in relation to crop growth stage and residual biomass, influences crop recovery and yield potential.
• Good livestock prices have highlighted the profitable and flexible options for DP crops under different seasonal conditions.

Background

In southern NSW, outputs from experimental research and grower experience over two decades has firmly established dual-purpose (DP) crops (both cereals and canola) into mixed farming systems. Crops are grown across a wide range of environments from Feb-March sown winter crops, a mix of winter and spring varieties sown in March and April and opportunistic grazing of April-sown spring crops. Systems experiments, simulation and the early adopters in the district have demonstrated that the benefits to whole-farm businesses can increase whole-farm profit by more than $100/farm ha, i.e. across the entire farm, not just from the paddock used for dual-purpose production. Well-managed crops can provide significant forage with none or little impact on grain yield (Table 1). Appropriate integration of DP crops provides growers with increased profit, flexibility and risk management strategies. Here we present findings from almost two decades of research on DP crops with the aim of highlighting the main messages and considerations for successful adoption.

Table 1. Typical examples of forage, grain yield and gross margins achieved from well-managed dual-purpose crops by collaborating growers in medium/high rainfall zones of southern NSW. DSE = dry sheep equivalent.

What are some of the key agronomic practices needed to successfully establish dual-purpose crops for maximum grazing potential?

Consider the fit of dual-purpose crops for your enterprise

A livestock plan is important to ensure that you optimise profit from the extra feed provided by DP crops. Consider the potential dry matter available and feed requirements of livestock. Canola has higher growth rates than cereals under ideal autumn conditions (up to 100kg DM/ha/day) but is lower than cereals once conditions cool into winter. Early-sown cereals can offer the potential for multiple periods of grazing but due to the slower adaptation to feed by livestock and slower recovery, canola is better suited to a single, extended graze.

Early establishment with the right variety is the key to success

Successful establishment in the earliest window with the right variety to flower at the optimum time provides maximum grazing potential. Grazing potential of wheat declines by 200-250 DSE.days/ha for every week’s delay of sowing after March 1. There are a variety of things to consider for successful establishment and protection to maximise forage:

1. Select a suitable paddock and be prepared to sow early! Consider weed control, chemical with-holding periods, stubble management, and stored water for early-sown crops which is particularly important for small-seeded canola.
2. Sow early with the right crop and variety to ensure flowering at the optimum time. Grazing can delay the onset of flowering, however, selecting the right cultivar ensures the correct flowering time if the crop is not grazed or is grazed unevenly. Early-sown, slower-maturing crops have the longest vegetative period and provide the most grazing potential, but typical grain-only spring crop varieties can also be sown early, and provide useful grazing without significant yield loss following the same principles – but the potential grazing is much reduced (Figure 1), and closer management of lock-up timing is required to ensure that crops are not over-grazed. Though different strategies and crop types are better suited to different regions due to the rainfall and season length, a mix of the different approaches shown in Figure 1 can be used on the same farm to take advantage of early sowing opportunities in specific seasons to increase and widen the overall operational and crop grazing window.
3. Protect early-sown crops from establishment pests and aphids that transmit virus. Seed dressings are affordable and effective, but follow-up aphid sprays in warm autumns may be required if aphids persist due to Barley Yellow Dwarf virus. Winter canola tends to carry over aphids through colder weather as they persist deep in the rosette.
4. Aim for a good plant population for good early biomass production for grazing: 150 plants/m² for wheat; 40 plants/m² for canola.
5. Ensure sufficient nitrogen (N) up-front (soil and fertiliser) for good early biomass production. Canola is more responsive than wheat to nutrition.
   1. 100-150 kg/N for winter wheats and canola; 50-100 kg/ha for spring wheats and canola.
   2. the seasonal N requirements for grain yield are 80kg N/tonne for canola and 40kg N/tonne for wheat. Top-dress post-grazing to available N and target yield.

Figure 1.  Increased grazing window of winter varieties in longer-season areas compared to spring types in the cropping zones. (Typical windows shown are S=Sow, Gr=graze, F=flowering, H=harvest).

What do we need to know regarding management of livestock?

Lockup time is the critical management decision to maximise profit from both the stock and the crops.

Stock

Liveweight gain on DP crops can be up to 2.5kg/hd/day for cattle and 350g/hd/day for sheep. However, animal health issues are a concern, and therefore, close management is required. Grazing canola poses greater risks than cereals, particularly for cattle, and for this reason many growers in southern NSW only put cattle onto cereals. For canola, introduce stock slowly with a full stomach, to avoid gorging and bloat, and monitor regularly. Consecutive days of frost have been associated with bloat in cattle as animals don’t feed on frosted crops and then gorge themselves. Provide hay as an alternative feed or consider removing stock under these conditions. Nitrate poisoning can occur in highly fertilised crops (apply N at least three weeks prior to grazing) and is more prevalent under cloudy conditions. Photosensitisation (swelling, blistering and scabbing on exposed face and ears) is caused by grazing stock, especially young lambs, on young Brassica crops. There are few animal health issues for grazing wheat, however, a supply of mineral supplements (Causmag) can increase liveweight by up to 20-30%. Mineral supplementation has not shown benefits for grazing canola.

Aim for stocking rates of approximately 1000kg/ha liveweight but adjust for feed on offer. Canola is best grazed for an extended period of time as animals require a period of adaptation, so lower stocking rates may be required.

Crops

Don’t graze too early as crops are building root mass and growth can be checked or plants pulled out. To check when crops are ready, twist and pull to ensure the crop is well anchored. Crops usually need at least 1.5t/ha biomass (~6-8 leaf stage in canola).

Experiments have shown that crops can be grazed without a yield penalty, but how can we understand this?

The yield potential of any grain crop is related to the biomass at anthesis to support grain-filling. The yield achieved then depends on conditions during flowering and grain fill to realise the potential. In Australia, because crops grow the biomass from autumn to early spring, but flower and fill grain as conditions are getting hot and dry, they almost always grow more biomass than what will be needed for the grain yield that can be achieved.  For example, a rule of thumb is that each 1t/ha of wheat grain yield needs 1.8t/ha of biomass at flowering (i.e. 3t/ha crop needs 5.4t/ha of biomass at flowering, etc.). Well-managed, early-sown crops in medium and high rainfall areas often produce significantly more biomass at flowering than is needed for the likely grain yield.  This explains why we can use some of this excess biomass with careful and timely grazing, and still achieve the target yield.

The ‘safe’ grazing period for cereal and canola crops is from the time the crop is well anchored until the reproductive parts start to elongate above the ground and can be damaged or removed by the livestock (DC30 for cereals and bud elongation for canola).  Any crop can be grazed in this window and grazing will usually delay flowering from a few days to two weeks, depending on grazing duration and intensity.

Crop recovery - safe lock-up and grazing rules

Grain yield penalties occur when grazing too late (i.e. removing reproductive parts) and too hard (leaving insufficient biomass to reach target yield). The decision is significantly influenced by the crop yield outlook and the relative prices for livestock and grain. These different ‘exit options’ depending on circumstances provide significant flexibility.

The ultimate goal for managing DP crops is to maximise the profit from the combined income from the grazed forage and the grain.  This requires an understanding of how grain yield is affected by heavier or delayed grazing.

Our studies have demonstrated that the time of lock-up and the residual biomass are the critical issues.  We can define the overall grazing window into ‘safe’, ‘sensitive’ and ‘unsafe’ periods related to the impact on grain yield (Figure 2).  The early and ‘safe’ grazing period is once the crop is well anchored and there is still plenty of time for recovery after a period of grazing, even if the crop is grazed quite heavily.  The late and ‘unsafe’ period is when the reproductive parts of the crop (spikes in wheat, or buds in canola) are elongating above the ground, and can be removed by stock, and there is also too little time for the crop to recover enough biomass by anthesis to set a reasonable yield potential.  Most growers can easily identify these two periods by testing crop anchorage to start grazing and checking crop development stage to stop grazing.  The ‘sensitive’ period is the period in which the crop has not yet begun to elongate, but where yield recovery can be very sensitive to the amount of residual biomass left.  This is the period where some idea of how much residual biomass is needed to reach a specified target grain yield can assist growers with lock-up decisions to avoid yield loss while maximising grazing potential.

Figure 2. Yield recovery (% of un-grazed crop) of grazed dual-purpose crops highlighting the safe, sensitive and unsafe periods of grazing.  Yield recovery from grazing during the sensitive period for a given target yield is affected by the residual biomass at lock-up.  Late grazing reduces the time for recovery, so more residual biomass is needed.

Experiments with different times and intensity of grazing have been used to investigate the relationship between: Residual Biomass (lock-up) <=> Critical Biomass (anthesis) <=> Target Yield.

A range of different winter and spring wheat and canola crops were used in the studies. An example is that a typical grazing EGA Wedgetail wheat crop sown on 25 March with a target yield of 4.5t/ha would require a critical anthesis biomass of around 8 to 9t/ha (Figure 3A). This critical biomass would require at least 0.5t/ha of residual biomass to be left in late July (Figure 3B), when the crop becomes unsafe to graze without removing elongating heads (i.e. heads removed if past DC30). Grazing past this point would require close attention to grazing height to ensure heads were not being removed, and more residual biomass (1.0 -1.5 t/ha) would be needed to be left at lock-up in mid-August to still achieve the same critical anthesis biomass, because there is less time left to reach the biomass for the target yield. Note that the spring wheat EGA Gregory sown on 8 May generally had similar critical and residual biomass levels to attain similar yields.

For canola, the residual biomass requirement after grazing is higher than wheat, due to the inherently heavy and thick stem bases and slower regrowth after grazing. Spring canola requires about 1.5t/ha of residual biomass left when locked up at the end of July (when the stems begin to elongate) to ensure 2.5 to 3.0t/ha yield potential. Earlier-sown winter canola has even thicker stem bases and requires around 2.5t/ha of residual biomass for recovery.

Figure 3. (A) – Shows that for a 4.4t/ha target yield in wheat, around 8.0 to 9.0t/ha was required at anthesis, and treatments with less than this had reduced yield. (B) Shows that residual biomass after grazing of >0.5t/ha in late July was sufficient to reach the critical anthesis biomass for 4.4t/ha yield.

What practical takeaways can growers get from looking at the trial work?

Trial work underpinning the key strategies for success have been outlined in the preceding section, however, there are a number of other things to consider.

Trade-offs and economics

Ultimately economics (feed value vs grain value) in the farm enterprise dictates the acceptable level of grain yield loss (if any) for DP crops. In many cases, especially where the feed is being used to fatten or finish lambs or cattle, it is possible that accepting a grain yield penalty makes the most economic sense, as shown for the moderately grazed crop shaded in Table 2.

Table 2. Amount of grazing achieved and grain yield from different grazing treatments in an EGA Wedgetail crop at Greenethorpe, NSW, sown on 15 March 2013. Income was highest with a small grain yield penalty as the extra grazing was more profitable than the yield lost. The crops received 333mm of GSR (Apr-Oct) but spring conditions were very dry so crops largely filled on stored soil water.

(Economics calculated at $250/t grain and grazing at $0.38/sheep grazing day (i.e. $1.7/kg LW for a sheep growing at 225g/day and eating 1.5 kg biomass/day)

Spring wheats such as Gregory can also be grazed with success, but due to the later optimum sowing dates and smaller safe grazing window (Figure 1, the amount of grazing achieved is much less (Table 3). The effect of grazing too late and/or leaving too little residual biomass (<0.5 t/ha) can be seen to impact on the economic outcome. In this case with spring wheat, yield was only maintained with later grazing if a large amount of residual remained, and this did not match the economics of grazing hard earlier to provide time for recovery. In general, a much greater level of attention is needed to manage the timing of lock-up in spring crops as development is rapid and the plants less robust. But grazed spring wheat and canola crops can widen the crop-grazing window at the farm-scale, allowing significant spelling of pastures.

Table 3. Amount of grazing achieved, grain yield and additional income from different grazing treatments in a Gregory wheat crop at Greenethorpe, NSW, sown on 28 April 2014. The best outcome was to graze safely with economic penalties for later or harder grazing. The crops received 333mm of GSR (Apr-Oct) but spring conditions were very dry so crops largely filled on stored soil water.

Exceptional performance in drought but legacies must be managed

Early-sown DP wheat and canola options have been highly profitable at GRDC farming systems sites at Greenethorpe and Wagga Wagga, NSW, in two recent decile 1 seasons in comparison with timely-sown grain only crops (Table 4). However, the success largely depended on deep stored water from either summer rainfall and good fallow management, or sequences with legumes which left legacies of water and N. At Greenethorpe, consecutive early-sown DP crops (phased canola and wheat) were able to capitalise on higher amounts of stored water to produce more than three times the profit achieved by a grain-only (or hay) system ($1122/ha vs $334/ha). At Wagga Wagga, under drier conditions, income for the same DP crops declined in the second year in 2019 due to the legacy of drier soil from 2018, but the DP system still had higher profit than the grain-hay system ($379/ha vs $172/ha). In medium rainfall areas, selecting the paddocks and seasons to go for early-sown winter options can maximise profits.

Table 4. Annual and 2-Year profit (EBIT) at Greenethorpe and Wagga Wagga, NSW, for early-sown (March) dual- purpose canola-wheat systems compared with timely sown (April) canola-wheat grain-hay systems in 2018 and 2019. Systems were phased (both crops were grown in each year).

Conclusions

Dual-purpose crops provide a range of direct and indirect benefits at the farm scale, however, attention to detail is required to optimise profits. Preparation and planning is crucial for early establishment which will maximise forage production. Monitor animals to avoid health issues, particularly for canola, and consider both crop development and residual biomass at lock-up. Other considerations include the trade-offs between grazing and grain value, and seasonal legacies.

Acknowledgements

The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC, the authors would like to thank Rod and Nick Kershaw, ‘Iandra’ for the use of land since 2013; Peter Brookes, Angus Gibson and James Cheatham (DeltaAg) for supporting research at Goulburn.

Useful resources

Maximising systems benefits from dual purpose crops - early sowing and grazing strategies. 2019 GRDC Update paper

Dual purpose crops - direct and indirect contributions to profit. 2020 GRDC Update paper

Contact details

Susan Sprague
CSIRO Agriculture and Food, Canberra
(02) 6246 5387, 0466 643 227
Susan.Sprague@csiro.au

John Kirkegaard
CSIRO Agriculture and Food, Canberra
(02) 6246 5381, 0459 354 630
John.Kirkegaard@csiro.au
@AgroJAK