Paddock Practices: New resource gives growers the right advice on early sown wheat

Key points

• Achieving optimal flowering can make a big difference to yield and profit
• Farm location and paddock selection are important considerations for early sown wheat
• The difference between dry sowing and early sowing must be understood
• Yield penalties can occur if crops are sown too early
• Using the right cultivar for environment and sowing date is critical for success
• A decision support tree is provided to help growers bring information together and apply it on-farm

Growers in South Australia, Victoria and southern New South Wales looking to capitalise on early autumn rainfall by sowing winter wheats early can look to a new resource developed by the GRDC to help them increase their chances of success.

Ten Tips for Early Sown Wheat covers a range of considerations for sowing wheat early including location, paddock selection, dry sowing, soil moisture, cultivar choice, crop protection, grazing and nitrogen.

Combined, these considerations can help growers to achieve flowering in the optimal flowering period from early sowing opportunities, which is a short period in spring (approximately 10 days) during which crops must flower to maximise yields.

Achieving optimal flowering can make a big difference to yield and profit and costs very little to achieve. However, there are some challenges to consider when sowing wheat early.

Tip #1: Consider your location

Location and prevailing climate can influence when the optimal flowering period occurs. Ten Tips for Early Sown Wheat provides the optimal flowering date for key locations across the southern region and the germination date to achieve the highest yield of a fast spring cultivar such as Scepter.

The publication advises growers in frost-prone areas to have the crop flowering seven to 10 days later by delaying sowing or using a variety with a slower development pattern.

Tip #2: Paddock selection

Weedy paddocks and paddocks with high levels of soilborne diseases such as crown rot and Rhizoctonia can hamper the development of early sown crops.

Growers sowing wheat early should aim to do so following break crops or long fallows with low weed and disease burdens.

Prudent summer weed control, is an essential consideration when planning for early sowing, as it not only helps save soil moisture and nitrogen but also removes volunteers which can host diseases and virus vectors.

Another key element for early sowing paddock selection, is the use of robust pre-emergent herbicide packages, particularly if the paddock has high grass weed pressure.

Tip #3: Dry versus early sowing – know the difference

Early sowing of winter wheats when moisture is available and dry sowing are both useful tactics for reducing logistical pressures at sowing and getting crops to flower during the optimal flowering period. They can be used in tandem but should not be confused.

Winter wheat cultivars that have a cold requirement before they will flower are most suitable for sowing in early April. These cultivars should be sown into a moist seedbed following rain or preceding a convincing forecast of enough rain to allow germination. This is what is defined as early sowing.

Dry sowing uses standard fast-developing spring cultivars sown into dry seed beds, usually in late April or May, so they will establish when breaking rains eventuate.

Sowing winter wheats into dry soils in early April may be a risky option, because if it does not rain until June, these may not flower in the optimum period and will be lower yielding than spring cultivars. However, research is still ongoing in this space.

Tip #4: Consider seed bed and stored soil water

At least 15 to 20 millimetres of rain are required for consistent germination of early sown crops, even when there is stored soil moisture, although less rain may be required on lighter textured soils.

Wheat seedlings are quite hardy and, provided they are sown after 1 April, this amount of rain is usually enough to keep them alive until cooler weather and further rain arrives in winter.

Shoots may become dehydrated but generally regrow once rain arrives.

Tip #5: Don’t sow too early

As a general rule, sowing winter wheat prior to 1 April results in a yield penalty, which becomes greater the earlier it is sown. Sowing earlier in March is only advised if grazing is the primary intention.

Tip #6: Use the right cultivar for the right sowing date

Matching the cultivar to the sowing date is crucial when sowing wheat early.

Slow-developing cultivars are required for April sowing so they take advantage of the longer growing season and flower during the optimal period. If fast spring wheats are sown in early April, they will flower before the optimum time, accumulate insufficient biomass and be exposed to excessive risk of frost damage.

To help growers make the right cultivar decisions, Ten Tips for Early Sown Wheat provides the development speeds of popular wheat cultivars grown in Australia and their suitability for early sowing.

The publication also features a graph which demonstrates the relationship between germination date and yield for winter and fast spring wheat. The stable flowering time of winter wheat gives it a stable yield over a wide range of sowing dates.

Tip #7: Use the right cultivar for the right environment

Different locations and climates across the southern region will require different cultivars in order to hit the optimal flowering period.

As a general rule:

• Warm, low-rainfall environments with early optimal flowering periods are better suited to fast winter cultivars
• Medium to low-rainfall zones are better suited to mid-winter cultivars
• High-rainfall zones with a late flowering window are better suited to slow to very slow winter cultivars

Tip #8: Protect crops from virus vectors

There are a number of management tactics for growers to consider to protect early sown crops from aphids and mites which may transmit viruses. These include:

• Summer weed control (see Tip #2)
• Cultivar choice – select those with some level of resistance to viral diseases
• Registered insecticidal seed dressings such as imidacloprid
• Follow-up spray applications of registered insecticides after the start of tillering if warm conditions and aphids are present

Tip #9: Graze early sown crops if you want

Growers may consider grazing early sown wheat as these crops can provide good early forage to fill a feed gap. This can be done with only a small yield penalty, provided soil moisture is sufficient for early growth.

The size of the yield penalty will also depend on the timing of livestock removal and the amount of residual biomass.

To minimise the grain yield penalty, it is advised to remove livestock early, or to not graze as hard and leave more green leaf area.

Tip #10: Adjust plant density and nitrogen fertiliser

The target plant density and nitrogen requirement will depend on what the crop will be used for, whether that be grain only or for grazing and grain.

Early sown wheat to be used for grain only, performs best with plant densities of between 50 plants per square metre and 100 plants/m². Growers sowing wheat early sown for grain only are advised to delay application of nitrogen during early stem elongation, between growth stage 30 and 32.

Growers sowing wheat for dual-purpose are advised to aim for populations of at least 150 plants/m². In this situation, applying nitrogen at seeding, and a total nitrogen supply which includes soil mineral nitrogen of 150 kilograms per hectare will maximise forage yield.

Putting it all together

To help growers bring the above points together, Ten Tips for Early Sown Wheat has a decision support tree which provides a summary of the overall management package and a guide on how to get the most out of early sown winter wheat crops.

This information has been brought together through a range of past and current GRDC investments in partnership with La Trobe University, New South Wales Department of Primary Industries, the South Australian Research and Development Institute, Agriculture Victoria, Birchip Cropping Group, Hart Field Site Group, FAR Australia, Frontier Farming Systems, Central West Farming Systems and Ag Grow Agronomy and Research.