Newly harvested plots have revealed that wide row spacings can choke wheat yields, dropping returns by up to $85 per hectare.

Although wide rows may suit lupins, Grains Research and Development Corporation (GRDC) upported research by ConsultAg revealed that when row spacings extended from 225 mm apart to 450 mm on a 4 t/ha wheat plot at Pingrup, yield declined at a rate equivalent to 2 kg/ha/mm.

This supports Department of Agriculture findings at East Hyden in 1995, where increased row spacing dropped the yield of a standard 2 t/ha crop by 1 kg/ha for each extra millimetre of row width.

ConsultAg’s Steve Curtin said that in this year’s trials, the leap to a 450 mm row spacing cut yields by 12 – 15 per cent, equating to a $85/ha profit loss on current prices.

“Our trials were intended to see if wider rows protected wheat crops from the impact of frost because it was thought temperatures rose higher between wide rows during the day to provide a heat cushion for the evening,” he explained.

“Plots were sown at 225 mm and 450 mm row spacings at a seeding rate of 65 kg/ha. It was probably the intense competition between wheat plants sown using wide rows which resulted in 15 per cent fewer plants establishing.

“Ongoing competition meant 30 per cent fewer wheat heads were produced and despite the plant’s natural compensation, this resulted in yields dropping.”

Supported by growers and the Federal Government through the GRDC, the ConsultAg trials incorporated Yitpi as a tall, late maturing variety and Wyalkatchem as a short, early maturing variety, with some plots sown to a 50/50 mix.

Yields from the mix landed halfway between the Yitpi yields and the frosted Wyalkatchem yields, indicating that blending varieties of different stature and maturity could help manage frost risk.