Research with GRDC and NSW Department of Primary Industries investment through the Grains Agronomy and Pathology Partnership has shown improved canola establishment can be achieved by:
- Stubble removal before sowing
- Shallow seed placement
- Reducing sowing speed
- Separating fertiliser from the seed.
NSW Department of Primary Industries (NSW DPI) researchers have confirmed the critical factors needed for effective canola establishment.
Lead researcher, NSW DPI agronomist Colin McMaster, says canola establishment is an issue in central NSW because of increased seed costs, reduced sowing rates, unreliable autumn rainfall and sowing into marginal seedbed conditions.
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Canola seed costs from 1990 to 2010 were relatively stable at four per cent of total input costs, but increased to 14 per cent of total input costs in 2018, he says.
The increased seed cost is largely related to the dominance of hybrid over open-pollinated (OP) varieties from 2011 to 2018.
Mr McMaster says the target plant density during the era that OP varieties dominated the marketplace (pre-2010) was 50 to 80 plants per square metre and the target seeding rate was between three and five kilograms per hectare.
Since the adoption of hybrids, the target plant density has reduced to about 20 to 50 plants per square metre, depending on rainfall zone, he says.
Currently, best management practice is to first determine the target plant density for your rainfall zone and then calculate seeding rates via knowledge of seed size, germination percentage and an estimate of the establishment percentage.
Canola seed costs from 1990 to 2010 were relatively stable at four per cent of total input costs, but increased to 14 per cent of total input costs in 2018
Mr McMaster says recent developments in understanding variety phenology, sowing time and the adoption of slower-developing spring varieties has bought forward the sowing window from 25 April to early April for slower-developing spring types.
A broader, more flexible sowing window enables canola establishment to occur when rain falls, rather than waiting for the traditional Anzac Day trigger to initiate sowing, he says.
This greatly improves the flexibility of the farming system. However, establishing canola in early April has the disadvantage of higher seedbed moisture dry-back due to increased evaporation caused by higher temperatures.
Currently, best management practice is to first determine the target plant density for your rainfall zone and then calculate seeding rates via knowledge of seed size, germination percentage and an estimate of the establishment percentage
By way of example, Mr McMaster points to the medium rainfall area of Parkes, NSW, and says average daily evaporation reduces from 5.9 millimetres in March, to 3.7mm in April and 2.2mm in May.
This means that a shallow-planted canola seed is at higher risk of moisture dry-back if sown in early April compared with May, particularly in the warmer regions of NSW, such as Condobolin, he says.
To benchmark current canola establishment percentages and evaluate the management practices that influence canola establishment, Mr McMaster and his NSW DPI colleagues Ian Menz and Allen Stevenson measured canola establishment across 95 paddocks in the low, medium and high-rainfall zone of central NSW.
Paddocks were selected to include various combinations of stubble management (burnt, retained and cultivated) and seeding system (knife point and press wheel, disc or scatter plate).
The survey design allowed for 10 paddocks with each combination of stubble management and seeding system from each rainfall zone.
Plant establishment was measured across 15 x 1m2 quadrants per paddock.
From this, an establishment percentage was determined through knowledge of seed size and sowing rate.
Plant population and uniformity was measured via the development of the vacancy percentage method.
This used a 1m2 section of mesh with 10-centimetre squares to count both plants, as well as total number of vacant squares.
Other data collected included sowing date, sowing depth, fertility rate/placement/type, variety, sowing rate and GPS coordinates, sowing speed, soil type, seedbed moisture and crusting events that occurred after sowing.
Mr McMaster says a wet March and some timely rainfall events in April allowed canola to be sown into favourable seedbed conditions across the low, medium and high-rainfall zones of central NSW during 2017.
March rainfall was above the long-term average at Condobolin, Parkes and Cowra, with an additional 41, 56 and 49mm above the long-term average rainfall, respectively, he says.
Seedbed moisture conditions were favourable at the start of April and then started to decline from mid-April onwards.
He says additional rainfall around Anzac Day ensured favourable crop establishment for most of central NSW. In the paddock survey, he says the earliest, median and last sowing date was 10 April, 22 April and 10 May, respectively.
Seed size was the main differentiating factor that improved canola establishment.
Across the 95 survey paddocks, 44 were hybrid and 51 were OP, he says.
The breeding type selected was largely influenced by growing-season rainfall and the length of the growing season, with hybrids dominating the high-rainfall zone, OP the low-rainfall zone and an even split between hybrid and OP in the medium-rainfall zone.
Across the 51 survey paddocks that were OP, Mr Mc Master says 16 paddocks were purchased seed and 35 paddocks were grower-retained seed.
Of the 35 grower-retained seed paddocks, he says only four were not graded to seed size.
Seed size grading ranged from 1.6 to 2mm sieve size; however, the sieve size was determined by the ratio of total seed graded to how much seed was required for the following sowing, he says.
Across all the paddocks, the average sowing rate was 2.5kg/ha for OP (which ranged from 1.6 to 4kg/ha) and 2.4kg/ha for hybrid (0.9 to 3.2kg/ha), with the average seed size from the hybrids 4.9g/1000 seed (203,610 seeds/kg) and 3.9g/1000 seeds (257,106 seeds/kg) for the OP.
Mr McMaster says the average establishment was 48 per cent, with most paddocks ranging between 38 and 58 per cent.
Establishment improved from low to medium to the higher-rainfall zone, with the low, medium and high-rainfall zones achieving 43, 47 and 55 per cent establishment, respectively, he says.
The main factor that differentiated establishment percentage was seed size, however this trend was not linear (see Figure 1).
The mean seed size was 4.3g/1000 seeds and ranged from 3.3 to 6.6g/1000 seeds.
In addition to seed size, Mr McMaster says a six per cent increase in establishment resulted from planting hybrid canola (51 per cent establishment) rather than OP canola (45 per cent establishment).
After seed size, the agronomic practices that influenced canola establishment were the sowing system, stubble management, sowing speed and phosphate fertiliser placement, he says.
On average, reducing stubble loads by either burning or cultivation improved canola establishment by 10 per cent.
He says the main benefit appears to be from the physical removal of the stubble, rather than the cultivated seedbed.
Mr McMaster says old sowing technology such as scatter-plates, which broadcast seed on the soil surface, performed well.
It is likely that the main benefits of the scatter-plate seeding system were due to shallow seed placement and favourable autumn conditions in 2017, he says.
On average, the highest establishment of 58 per cent was achieved with scatter plates, and then reduced to 49 and 41 per cent with knifepoint and disc seeding system, respectively.
Mr Mc Master says establishment decreased as sowing speed increased, with a 16 per cent establishment reduction if speed increased from 6 to 8 kilometres per hour to 13 to 17km/h.
The results also showed there was a seven per cent reduction in establishment if phosphate fertiliser was not separated from the seed, he says.
Despite favourable sowing conditions during 2017, Mr McMaster says the results show there is an opportunity for improved canola establishment in central NSW.
Effectively, growers are only establishing half of what they purchase, and if the autumn break is less favourable, its likely to be much less, he says.
Traditionally growers would sow an extra 1 to 1.5kg/ha of seed to compensate for poor sowing conditions; however, this is no longer an option given the associated higher costs with hybrid seed.
Mr McMaster says seed size was the main differentiating factor that improved canola establishment and the other key agronomic practices were stubble removal, reduced sowing speed, shallow seed placement and separating phosphate fertiliser from the seed.
Hybrids seeds are generally larger in size and establishment was better than OP varieties, he says.
Further research is needed into why the relationship between seed size and establishment was not linear (Figure 1).
Mr McMaster says the benefits of the scatter-plate seeding system in 2017 were likely to be associated with shallow seed placement combined with weather conditions that provided moist conditions for canola seedlings to germinate and establish.
Canola establishment results are likely to be different if moisture seeking is required, he says.
These experimental results show the importance of carefully setting up seeding equipment, particularly with disc-seeding systems. As these are typically used in high-stubble-load paddocks, sowing speeds are higher and there is limited fertiliser-seed separation.
GRDC Research Code BLG110
More information: Colin McMaster, NSW DPI, 0427 940 847, firstname.lastname@example.org
Read more: 2018 Wagga Wagga GRDC Updates paper