Northern research measures dual-purpose profitability
GroundCover™ Issue: 109 | Author: Bob Freebairn - Agricultural consultant, Coonabarabran, NSW
Dual-purpose winter grains for grazing and cropping are planted to a relatively small area in the northern grain-growing region, but GRDC-funded research has shown the significant profit potential of this versatile system in this region.
Leading the research, Dr Lindsay Bell and his team from CSIRO Farming Systems have examined the potential yield of dual-purpose crops following grazing, plus the productivity of long and short-season varieties.
Previous research in the southern grain-growing region by CSIRO and the New South Wales Department of Primary Industries generally showed a small yield penalty in dual-purpose varieties after grazing, but in some cases a yield increase was also noted.
In northern farming systems, especially in hot, dry areas, research indicates the risk of yield penalties may be considerably greater in this region because dual-purpose crops have less time to recover from grazing in warm conditions.
However, yield is not the only consideration.
Dr Bell says dual-purpose crops can be a profitable option because they provide quality feed when pasture supply tends to be limited, in May, June and July, and also in August in colder environments.
Another benefit, particularly in the northern grains region, is that dual-purpose crops can often be sown earlier than conventional grain-only crops, increasing the sowing window. For example, in many years it is possible to sow a dual-purpose crop early, providing a significant gain if later seasonal conditions prove too dry or wet to sow winter grain crops.
In the case of dual-purpose canola, another advantage is that it can be used as a break crop option to help control disease, for example, crown rot, and also to vary herbicide use. Grazing cereals and canola can also bring down the height of crops to facilitate windrowing and harvesting.
Overall, grazing cereals and canola add to income flexibility and profitability depending on crop and livestock markets.
Relative grain yield
As part of the GRDC-funded Grain & Graze 2 program, demonstration sites in the Warialda, Coolatai and Inverell districts of NSW comparing the yield impact of defoliation have shown that early defoliation in grain-only crops results in small yield penalties. Project officer Nicole Gammie says the average yield penalty following defoliation was 0.2 tonnes per hectare, although three defoliated grain-only crops still yielded higher than the non-defoliated control.
Ms Gammie says the yield penalty was smaller when slower to mid-maturing varieties that produce more biomass were sown early.
She says that seven of the 10 demonstration sites returned more income from dual-purpose crops compared to grain-only crops.
The research by Dr Bell also assessed the likely yield penalty of defoliation in a wide range of environments from Pittsworth in southern Queensland and Gulgong in northern NSW to Quirindi and Gunnedah on the Liverpool Plains.
Dr Bell says returns from grazing generally offset grain yield losses in dual-purpose cropping. However, early seeding of slower-maturing varieties and careful grazing management can help to minimise grain yield penalties.
Research has shown that winter dual-purpose varieties provide the most grazing biomass, with early-sown, long-season cultivars producing enough biomass to support more than 2000 dry sheep equivalent (DSE) days per hectare in both the Tableland and Northern Slopes areas of NSW.
However, spring dual-purpose varieties can also generate substantial biomass for grazing. Spring wheat cultivars, such as EGA Gregory, typically produced 1.0 to 1.5t/ha grazing dry matter, with an estimated value of $100/ha to $150/ha.
In addition, the Grain & Graze research showed that greater early vigour growth in barley can provide more biomass for grazing than spring wheat varieties. In one farm demonstration, Ms Gammie found that Commander barley provided more than 2.5t/ha of grazing dry matter. Early-sown barley produced more grazing biomass with minimal yield penalties, she says.
Research in the northern grains region has highlighted the importance of restricting grazing to a crop’s vegetative period, prior to GS30 (jointing), to help maximise grain yields. Variety choice was shown to be important because grazing can delay crop development, with mid-season varieties allowing crops to be grazed for longer than short-season varieties.
Dr Bell also stresses the importance of adhering to herbicide and pesticide withholding periods before grazing begins.
Early sowing probability
Studies based on long-term climate data, which assessed the probability of being able to sow before the conventional ‘grain-only’ sowing period, indicated a 70 per cent chance of receiving enough rain to sow a dual-purpose crop early.
Suitable equipment, such as narrow points and press wheels, plus good fallow management (for high subsoil moisture levels) and stubble cover can also assist with early sowing. There is a greater probability of good early sowing conditions in eastern high-rainfall areas.
The studies by Dr Bell and Ms Gammie have shown that yields from grazing canola are less than cereals, but the oilseed crop provided high-quality forage, yielding about 1500 DSE grazing days/ha. Shorter-season spring cultivars also have potential to be used as dual-purpose crops, although they provide a shorter grazing period of between 20 and 30 days.
Dr Bell says that canola is a popular dual-purpose crop in the southern grain-growing region due to few issues with sheep grazing. However, in the northern region, there have been cases of nitrate poisoning and possibly bloat in cattle grazed on canola.
He suggests avoiding fertiliser applications shortly before grazing, monitoring animals regularly and following advice for forage brassica grazing.
The northern research has supported findings in the southern region that indicate magnesium and salt supplements for livestock when grazing wheat or triticale can improve animal weight gain by 25 per cent (steers from 1.13 to 1.40 kilograms per day per beast). Supplying animals with a 1:1 mix of Causmag:salt can be cost-effective using rates of 20 grams/head/day for sheep and 140g/head/day for cattle. But no advantage is expected from this supplement with oats or canola, and further studies are required to assess barley.
The nitrogen requirements of crops can more than double where growers aim to graze and achieve similar yields to ‘grain-only’ crops. The research has shown the need to carefully monitor crop nitrogen status and address deficiencies.
0409 344 072
Dr Lindsay Bell
07 4688 1221
GRDC Project Code DAQ00162, CSP00160
Region National, North