Early sowing lowers production risk
GroundCover™ Supplement Issue: 103 | 04 Mar 2013 | Author: Janet Paterson
Early-sown wheats included in the mix provide large yield boost and lower production risk
Slow-maturing wheat varieties sown early into stored soil water can yield significantly more than mid to fast-maturing varieties sown on time in mid-May, according to two years of on-farm research by the GRDC-funded Water Use Efficiency Initiative.
Yield advantages of between one and two tonnes per hectare from the early-sown, slow-maturing wheat variety EGA Eaglehawk were achieved at Temora (2011) and Junee (2012), NSW, compared with the mid-to-fast-maturing varieties LongReach Lincoln and EGA Gregory sown in early to mid-May.
Why do early sown crops yield more?
1. Deeper roots. Early-sown crops yield more in seasons
when the soil profile fills with water because the crop is able
to access more water and convert it into grain. Wheat roots
grow at about 12 millimetres per day from germination through
to flowering, so early sowing provides more time for roots to
grow to depth before grain fill.
2. Less evaporation. Early-sown crops also develop their canopy
faster and as a result lose less soil water to evaporation. This
enables proportionally more soil water to be converted
to dry-matter (Table 4).
3. Longer yield building phase.
The time available for stem elongation
is also longer in early-sown, slower-maturing wheat crops, enabling
them to intercept more radiation and generate higher grain numbers.
CSIRO scientist Dr James Hunt says the results are exciting and could provide growers in the region with a valuable way to increase yield and better manage wheat production risk.
In addition to the field trials, an Agricultural Production Systems sIMulator (APSIM) simulation study by Dr Julianne Lilley, CSIRO, indicated that including a slow-maturing wheat variety in a cropping program could significantly lift average farm wheat yield by 13 to 47 per cent and reduce by a third the risk of crops yielding less than 1t/ha.
Slow-maturing wheat varieties have been available for some time. Dr Hunt says the slow-maturing varieties could play an important role in modern cropping systems, which increasingly need to rely less on in-season rainfall and more on stored soil moisture from fallow rain events.
Larger farm sizes and increased cropping areas mean that modern sowing programs often exceed the available sowing opportunities.
Using early-sown, slow-maturing varieties as part of the cropping program mix would help to extend the sowing window and take advantage of stored soil moisture without incurring the frost risk associated with early-sown, faster-maturing varieties.
Dr Hunt and colleagues used 100 years of weather records and the on-farm simulation model APSIM to determine the optimal flowering window at three locations with contrasting climates: Lake Bolac, Victoria – high-rainfall zone; Temora/Junee, NSW – medium-rainfall zone; and Condobolin, NSW – low-rainfall zone. Optimal flowering dates were 23 October at Lake Bolac, 28 September at Temora/Junee and 16 September at Condobolin.
Commercially available and locally adapted spring milling wheat varieties of varying maturity were sown at each location on different dates so that they flowered on the identified optimal date.
Wheat varieties were classified as ‘very slow’ (Forrest at Lake Bolac and EGA Eaglehawk at Temora/Junee and Condobolin), ‘slow’ (Bolac at all sites), ‘mid’ (Derrimut) at Lake Bolac and EGA Gregory at Temora/Junee and Condobolin), ‘fast’ (LongReach Lincoln at all sites) and ‘very fast’ (Axe at Condobolin, 2011 only).
The optimal sowing date for the very-slow-maturity group was 15 April, with optimal sowing dates for subsequent groups increasing progressively by 10 days. Experimental sowing dates were slightly different but the maturity classes all flowered within the same week at each location (13 to 20 September in 2011 and 24 to 28 September in 2012).
At Temora in 2011 there was a large yield advantage from early sowing (15 April) of the very-slow variety EGA Eaglehawk at a reduced seeding rate to lift harvest index. EGA Eaglehawk yielded 6.3t/ha compared with 5.4t/ha for the mid-maturity variety EGA Gregory sown 9 May and 5.5t/ha for the mid-fast variety LongReach LincolnA sown 19 May (Table 1).
EGA Eaglehawk again performed extremely well when sown early at Junee in 2012 – yielding 2t/ha more than the mid-fast variety LongReach Lincoln sown on 17 May (Table 2). At the same site the yields of EGA Eaglehawk also surpassed the mid-fast variety EGA GregoryA sown on 8 May.
At the lower-rainfall site of Condobolin, similar yields in 2011 were achieved across all maturity ratings with dry conditions during late winter reducing grain set in the slow-maturing varieties (Table 3). The slow maturing varieties EGA Eaglehawk and Bolac sown early at low plant density yielded more than the same plant density of fast-maturing varieties sown later (LongReach Lincoln, Axe).
Putting it into practice
Establishing the optimal flowering window for a specific location is the most important requirement of an early sowing program. Once the flowering window has been established, varieties with a range of maturities can be chosen to generate a broad range of sowing dates. To achieve an optimal flowering time across the southern region it is important to:
- plant winter wheats from early March to mid April;
- plant slow-maturing spring wheats from early to late April; and
- plant mid-fast varieties from late April into May.
The first and second dots points above require at least 25 to 30 millimetres of stored soil water to be present at sowing. Use a shovel to check soil is wet to at least 30 centimetres on most soil types. As these crops are sown deep they must germinate and emerge shortly after they are sown or they will fail to emerge. Winter and slow-maturing spring wheats will flower too late if they do not establish before the end of April. Choose paddocks that are relatively weed-free and do not require a knockdown for grass weed control. Reduce seeding rates if sowing early into high soil nitrogen. Some diseases can be exacerbated by early sowing – for example, barley yellow dwarf virus, wheat streak mosaic virus, Septoria tritici and take-all. Seek appropriate control options.
| Variety and sowing date
|| Water use
| Total dry matter
| WUE for dry matter
| EGA Eaglehawk, 18 April
| Bolac, 26 April
| EGA Gregory, 8 May
| LongReach Lincoln, 17 May
Dr James Hunt, research scientist, CSIRO Plant Industry,
02 6246 5066,
GRDC Project Code CSP00111, SFS00018
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