23 September 2004: Following a dry winter, spring rain brings the temptation for growers to plant their grain sorghum early.

However, according to Pacific Seeds' Grain Sorghum business manager, Scott Gibson spring rains are often associated with a final cold snap which can affect germination and seedling vigour if planting occurs too early.

"One of the keys to reliable sorghum crop establishment is adequate seedbed or soil temperature along with sufficient but not excessive soil moisture," he said.

"The recommended minimum soil temperature for adequate germination and establishment is 17°C taken at 9am."
This temperature reading should be taken at planting depth over a number of days prior to planting to ensure the temperature is rising.

Some of the issues besides poor emergence arising from planting into cold soils are increased incidence of soil diseases, such as pythium or fusarium. It should also be noted that the longer it takes for a seedling emerge, the greater the chance of attack by soil insects.

"Variety choice can also affect germination in cold soils, for example under Pacific Seeds' grain sorghum breeding program and ongoing field test trials we've noted that MR-Maxi stands out as a good starter under cooler conditions," Mr Gibson said. "This variety, being medium maturity also has excellent yield potential, so should allow growers to capitalise on the early plant, especially if good in-crop rainfall occurs."

"However growers should note that we still recommend waiting for soils to warm for best germination and emergence."

"Traditionally on the central, western and northern Downs and in northern NSW planting times are normally early October with the eastern areas favouring late October."

"However with good rains in some areas, the temptation is there for many farmers to get a crop in the ground early, so we're warning growers of some of the risks."

In soil temperatures of 12°C, slow germination provides time for insect pests to attack seed in the soil and poor emergence is coupled with a risk of disease. At 15°C, satisfactory germination can be expected, however poor emergence and high disease risk can still be expected.

"Sixteen degrees provides good germination and adequate emergence, however 18-20°C is much better," Mr Gibson said.

"We urge growers to keep these figures in mind when planning their summer crop this season and to take a possible cold snap following the rain into account,"
"Basically, growers should remember that as a rule of thumb slower emergence will result in higher seedling mortality, and cool soil temperature certainly slows seedling establishment."

Caption:Pacific Seeds Grain Sorghum Business Manager, Scott Gibson.