More plants not an overall yield improver

Despite less plants a square metre being established, sowing into unfavourable conditions could be beneficial, rather than waiting for higher soil moisture, as the plant can compensate with an extended plant flowering window.

The University of Adelaide's Glenn McDonald and Hart intern Kady Morgan undertook trials at Hart, in the high-rainfall zone and north of Bute. The time of sowing project is funded for two years by SA Grain Industry Trust and the SA Drought Hub.

Associate Professor McDonald said the trial was driven by the increased size of cropping operations and growers sowing earlier.

"Growers are increasingly sowing into soil moisture which is not conducive to complete germination or in some cases, sowing into very dry soil," he said.

"So, it was important to look at the impact of dry seeding on crop establishment and the impact of varying crop establishment on grain yield."

Ass Prof McDonald said generally, in dry conditions, poorer establishment happens.

"The question is, is there a penalty associated with poor establishment? And, if there is, are there things growers can do such as increasing sowing density or sowing deeper to mitigate those effects," he said.

The plots had shallow, deep and standard sowing depth, and different sowing densities of standard, 25 per cent and 50pc higher sowing rates.

There were four sowing dates ranging from end of April to June 21 and three sowing depths of shallow, 1cm, standard, 1.5-2cm and deep, 3cm or more.

"We were looking to see if there are trade-offs between different times of sowing and how we can influence the response to different establishment rates," Ass Prof McDonald said.

Hart intern Kady Morgan said it was difficult to assess some of the trial results, as there was moisture present in the soil profile at the time of sowing.

"The first time of sowing was April 21 into about 25pc moisture because about 20 millimetres of rain had fallen," she said.

"So, it was not true dry seeding but it is a two year project and hopefully we will get a really early sowing date next year to see what happens with no moisture in the soil."

But, the best representation of dry or marginal sowing moisture was the second time of sowing.

"It was sown on May 5 into 11pc moisture which was a significant reduction from the first time of sowing. There was not any solid follow-up rain for three to four weeks after the sowing date either," Ms Morgan said.

Sowing canola crops into a lack of soil moisture can result in low plant establishment but the crop's ability to perform in dry conditions, means the outcome is not a total whitewash for yield.

A canola crop sown on June 20 had the highest plant establishment after it was sown into high moisture while another crop sown even later, also had high establishment but failed to grow above and beyond the earlier sown plots.

Hart intern Kady Morgan said those particular crops were visibly shorter and started to finish, despite the high plant establishment.

"It is important to know, even though the first two time of sowing plots had lower plant establishment, once the crop finishes flowering, you cannot notice too much of a difference because of canola's ability over-compensate for low plant establishment," she said.

"The second time of sowing had the lowest establishment counts out of all of the times of sowing because of not enough moisture in the soil to trigger the germination."

In the other plots, patchy establishment and effects from sowing depths was noticeable.

"The dry soil had caused some clotting while trying to get through the soil," Ms Morgan said.

"Even though the later times of sowing had high plant establishment, the first two sowings will have higher yields because of the longer growing season and flowering in better conditions."