Early sowing lowers production risk

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Two light blue water drops on a darker blue backgroundSlow-maturing varieties sown early increased WUE by 33 per cent at Junee in 2012 and 21 per cent at Temora in 2011 relative to early-mid maturing varieties sown in mid-May.

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 EaglehawkPBR logo were achieved at Temora (2011) and Junee (2012), NSW, compared with the mid-to-fast-maturing varieties LongReach LincolnPBR logo and EGA GregoryPBR logo 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.

Flowering windows

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.

Slow-maturing wheat varieties sown early into stored soil moisture can deliver significant yield gains while also extending the available sowing window – a real advantage in large cropping programs. Pictured is CSIRO scientist Dr James Hunt in a stand of the slow-maturing wheat variety EGA EaglehawkPBR logo, which, when used in combination with wheats with other maturities, can lift average farm yield by 13 to 47 per cent.

PHOTO: CSIRO

Wheat varieties were classified as ‘very slow’ (ForrestPBR logo at Lake Bolac and EGA EaglehawkPBR logo at Temora/Junee and Condobolin), ‘slow’ (BolacPBR logo at all sites), ‘mid’ (DerrimutPBR logo) at Lake Bolac and EGA GregoryPBR logo at Temora/Junee and Condobolin), ‘fast’ (LongReach LincolnPBR logo at all sites) and ‘very fast’ (AxePBR logo 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 EaglehawkPBR logo at a reduced seeding rate to lift harvest index. EGA EaglehawkPBR logo yielded 6.3t/ha compared with 5.4t/ha for the mid-maturity variety EGA GregoryPBR logo sown 9 May and 5.5t/ha for the mid-fast variety LongReach LincolnA sown 19 May (Table 1).

EGA EaglehawkPBR logo again performed extremely well when sown early at Junee in 2012 – yielding 2t/ha more than the mid-fast variety LongReach LincolnPBR logo sown on 17 May (Table 2). At the same site the yields of EGA EaglehawkPBR logo 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 EaglehawkPBR logo and BolacPBR logo sown early at low plant density yielded more than the same plant density of fast-maturing varieties sown later (LongReach LincolnPBR logo, AxePBR logo).

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.

 Table 1: Grain yield harvest index of four wheat varieties of different maturity sown at two plant densities in Temora, NSW in 2011 to flower on the same date.
Variety and sow date Grain yield (t/ha)
Harvest index (%)
40 plants/m2 100 plants/m2 40 plants/m2 100 plants/m2
 P-value  0.009  0.018
 LSD (p=0.05)  0.5  0.01
 EGA EaglehawkPBR logo (15 April)
6.3 6.0 0.41 0.39
 BolacPBR logo (27 April)
5.9 5.7 0.42 0.39
 EGA GregoryPBR logo (9 May)
5.0 5.4 0.44 0.43
 LongReach LincolnPBR logo (19 May)
4.8 5.5 0.44 0.44
Table 2: Grain yield of flour wheat varieties of different maturity sown at Junee, NSW 2012 to flower on the same date.
Variety and sow date
 Grain yield (t/ha)
50 plants/m2
100 plants/m2
 P-value  0.034
 LSD (p=0.05)  0.3
 EGA EaglehawkPBR logo (18 April) 5.9  6.1
 BolacPBR logo (26 April) 5.8  5.5
 EGA GregoryPBR logo (8 May) 5.1  5.2
 LongReach LincolnPBR logo (17 May) 4.3  4.0
Table 3: Grain yield and harvest index of five wheat varieties of different maturity sown at two plant densities at Condobolin NSW in 2011 to flower on the same date.
 Variety and sow date
 Grain yield
(t/ha)
 Harvest index (%)
 30 plants/m2
90 plants/m2
30 plants/m2
90 plants/m2
 P-value  0.029  0.027
 LSD (p=0.05)
 0.4  0.02
 EGA EaglehawkPBR logo (15 April)
3.4 3.1
0.37 0.32
 BolacPBR logo (27 April)
3.3 2.9 0.38 0.35
 EGA GregoryPBR logo (5 May)
3.6 3.2 0.44 0.39
 LongReach LincolnPBR logo (16 May)
2.8 3.0 0.46 0.45
 AxePBR logo (25 May)
2.1 2.6 0.45
0.44
Table 4: Crop water use (evaporation + transpiration), dry matter at maturity, WUE for dry matter and estimates of transpiration and evaporation for varieties of differing maturity sown in their optimal window at Junee, NSW in 2012.
 Variety and sowing date
 Water use
(mm)
 Total dry matter
(kg/ha)
 WUE for dry matter
(kg/ha/mm)
 Transpiration
(mm)
 Evaporation
(mm)
 EGA EaglehawkPBR logo, 18 April
345 11,756 34 214 132
 BolacPBR logo, 26 April
348 12,556 36 228 120
 EGA GregoryPBR logo, 8 May
344 9798 28 178 166
 LongReach LincolnPBR logo, 17 May
321 9229
29
168
153

More information:

Dr James Hunt, research scientist, CSIRO Plant Industry,
02 6246 5066,
james.hunt@csiro.au

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GRDC Project Code CSP00111, SFS00018