SPRING is here and summer-growing plants are starting to respond to the increasing soil temperature and longer days.
Now is the time to check soil temperatures and plant sunflowers.
Sunflowers can be sown earlier than the other summer crop options and develop a large tap-root system capable of seeking soil moisture from depths of 2 metres to 3m.
Sunflowers are also a good choice for paddocks where grass weeds are becoming a problem.
Australian Sunflower Association (ASA) committee member and Landmark senior agronomist Paul McIntosh says there are good reasons to get sunflowers planted early.
"In my experience sunflowers can be safely sown when the average soil temperature has risen above 6 degrees Celsius although to be on the safe side, the industry recommendation is to wait until soil temperatures are 10 degrees C at a depth of 10 centimetres," he said.
"Once this minimum temperature is reached it doesn't hurt to wait a few days extra just to be sure. It is important to sow sunflowers on a rising soil temperature trend
that is likely to continue for about 10 days to ensure strong, even germination."
Young sunflowers can handle light frosts but cool, wet soil conditions can increase the risk of seedling disease taking hold.
After planting, the seed imbibes soil moisture and the germination and emergence process starts - the most delicate phase of a plant's development.
Mr McIntosh warns a poor or very uneven strike will undo any potential advantage of sowing early.
The spring planting window for sunflowers has begun in central Queensland and will remain open until October in southern Queensland and northern NSW growing districts.
Measuring the soil temperature in the field will help make the planting date decision for a specific paddock.
To do this, obtain a reasonably accurate soil thermometer and bury the shaft of the instrument parallel to the ground surface at the potential seeding depth to simulate the seed trench environment.
"Take readings at about 8am in a few locations across a paddock," he said.
"There is likely to be some variation so pick out locations that are likely to be cooler due to their aspect and the lay of the land.
"Take another set of readings late in the afternoon."
Calculate the average morning soil temperature and the average afternoon soil temperature.
Add these two figures together and divide by two to give the average soil temperature for the day.
"One day of testing is usually not enough information so be prepared to do this for a few days before making the decision to plant," Mr McIntosh said.
"Depending on soil type, sunflowers require 80 to 100cm of wet soil at or soon after planting. They are also very sensitive to sulfonylurea (SU) and picloram herbicides so check the paddock history before planting."
ASA chairman Kevin Charlesworth says sunflowers are a consistent performer when it comes to gross margins for summer crops.
"When we workshop gross margins with growers sunflowers usually come out as second only to cotton," he said.
"This year there are two mono-unsaturated hybrids, one mid-oleic/birdseed hybrid and one grey stripe birdseed hybrid available for growers to choose from."
The Better Sunflowers website and the 'Big Yellow Sunflower Pack' are essential resources for new growers or those who have not grown sunflowers for a few years.
Provided there is adequate soil moisture, nutrients and weed control, sunflowers are a good option to sow early to convert millimetres of moisture into dollars over spring or summer.
