RiskWi$e EP – weighing up early sowing opportunities

This is part 3 of a three part series prepared for the RiskWi$e project by Andrew Ware, EPAG Research.

An early sowing opportunity, but not without trade-offs

One of the defining features of this season so far has been the opportunity to sow earlier than we’ve been able to in recent years.

With moisture sitting in the seedbed through mid-April, some growers have had the chance to get crops in and emerging under relatively warm conditions. That brings some clear advantages. Crops can establish quickly and build early biomass, and root systems can develop before soils dry out to avoid heat later in the season.

There are also some practical benefits:

• spreading the seeding program over a longer window
• reducing pressure on machinery and labour
• and avoiding the bottleneck that often comes with a late, compressed start

On paper, it looks like a good position to be in. But as is often the case, it’s not quite that simple. Taking the early sowing opportunity doesn’t remove risk—it changes where that risk sits. While warm soils and early moisture can support strong establishment, they also introduce a new set of challenges. The risk shifts from getting crops in the ground, to getting them established well and having their development properly aligned with seasonal conditions.

Lentils: well suited to early opportunity, but not without risk

As a relatively newer crop to the region, there’s still limited experience with how lentils perform when established as early as mid-April. There are a few characteristics that suggest they are well suited to taking advantage of early sowing opportunities, as lentils are an indeterminate crop, meaning flowering can continue over an extended period. This gives them some flexibility to respond to seasonal conditions, particularly if the finish is uneven.

There have also been some important shifts in recent years with improved herbicide tolerant varieties, better broadleaf weed control options and evidence that early vigour is strongly linked to yield.

Lentils can also be sown deeper into moisture, making establishment more reliable than some other crop types.

Taken together, these factors make lentils one of the more logical options for capturing early sowing opportunities.

Where the risk sits

That said, early sowing does shift some of the risk profile. Lentils remain susceptible to both vegetative and reproductive frost and earlier establishment may increase exposure to these events.

Building large early biomass can create challenges later in the season – dense canopies may increase disease pressure especially if spring conditions turn wetter.

Pulling it together

For many growers, lentils are likely to be one of the lower-risk options to start the program this year—particularly where moisture is sitting deeper in the profile, paddocks are suited to lentil production and early vigour advantages can be captured.

 

Canola: strong upside, but establishment risk is front and centre

Canola is another crop that can benefit from early sowing. Like lentils, it is indeterminate, with a long flowering window that allows it to respond to seasonal conditions. In lower rainfall environments in particular, early sowing can be advantageous as it allows crops to establish quickly, build biomass early and importantly, shift flowering and pod fill earlier in the season. Earlier sowing can help align these stages with cooler conditions, reducing the risk of yield loss later in the season.

Where the challenge sits

Despite this upside, canola is one of the more difficult crops to establish under these conditions. It is a small-seeded crop and needs to be sown shallow (typically 1–2 cm) to establish reliably.

Unlike lentils, it has very limited ability to chase deeper moisture. Recent research has shown that sowing deeper than 1–2 cm can significantly reduce plant establishment and yield. On average plant numbers were reduced by around 20%.

This places canola in a difficult position this year as moisture may be sitting just below the surface, but sowing shallow exposes the seed to rapidly drying conditions.

In mid-April, surface soils can also become quite hot – canola sown at 1–2 cm can experience temperatures approaching 40°C in full sun. That has two effects; moisture around the seed can be lost quickly and the environment for germination and early growth becomes more challenging.

So while canola offers strong upside with early sowing, the risk sits squarely at establishment.

For many growers, this means canola decisions will be highly paddock-specific, depending on:

• how close moisture is to the surface
• soil type and drying rate
• and the likelihood of follow-up rainfall

Cereals: the biggest risk is often not establishment, it’s timing

Cereals are a bit different to lentils and canola.

Our seeding systems are well adapted to effectively establish cereal crops. But when cereals are sown early, the main risk often shifts away from getting the crop up and onto getting its development aligned with the season.

That matters because flowering time is one of the biggest drivers of wheat yield. GRDC’s National Phenology Initiative highlights that wheat yields are maximised when flowering occurs in the optimal flowering period, where the crop is balancing the declining risk of frost against the rising risk of heat and water stress later in the season. That framing draws from research that showed that the optimal flowering period in south-eastern Australia is defined by the interaction of frost, heat and water stress, rather than temperature alone.

That is why early sowing of spring wheats can quickly become risky.

Using a Mace-type wheat at Minnipa as a guide, calculations show that if the crop germinates on:

• 15 April it may flower around 17 July
• 25 April around 1 August
• 1 May around 10 August
• 15 May around 28 August

The point is not that these dates will be exact every year. It is that development can move forward very quickly when spring wheats are sown into warm conditions in April. For many commonly grown spring wheats, development is driven largely by temperature, with only a modest vernalisation or photoperiod requirement, so sowing early can bring flowering forward faster than many growers might expect. The National Phenology Initiative was set up largely because matching cultivar development speed to sowing date and environment is so important for hitting that optimal flowering window.

Not all wheat varieties behave the same

One of the traps with early sowing cereals is assuming all wheats will respond in a similar way.

Many of the spring wheats currently grown on EP will behave broadly alike when sown early — that is, they will speed through development under warmer temperatures and longer autumn daylengths. But there are important exceptions.

Varieties with a stronger vernalisation requirement or stronger photoperiod sensitivity can hold development back for longer, which makes them better suited to earlier sowing. Winter wheats are the clearest example. GRDC material on flowering-time management consistently points out that slower-developing wheats are needed for very early sowing so flowering is not pushed too far forward into frost-prone periods.

A good current example is Mowhawk, a quick winter wheat. LongReach describes it as suited to early-break scenarios, with an optimal sowing window in SA/Vic from mid-April to early May. That makes it a very different fit to a typical spring wheat in an early sowing situation.

For cereals this year, the main question is not simply whether there is enough moisture to sow. It is: will this sowing date, with this variety, put flowering in the right part of the season?

That means cereals probably need to be thought about a little differently to lentils and canola.

• with lentils, the main attraction is their ability to take advantage of deeper moisture and flexible flowering
• with canola, the biggest risk is establishment
• with cereals, the biggest risk is often getting phenology wrong

So while early sowing can create real opportunity in cereals, it also puts more pressure on variety choice. If a spring wheat is pushed too early, the crop may flower too soon. If a slower type is chosen well, early sowing can become a genuine advantage.