Wide row spacings a hot topic

Specialised cultivars may need to be developed as farmers facing climate change continue the trend towards wider row spacings.

Curtin University Muresk researcher Hayden Sprigg has almost completed a PhD titled the Adaptation of Wheat Production in a Drying Climate.

Using field experiments and crop modelling, he investigated several management options reputed to increase water efficiency in a drying climate, including wide row spacings, delayed timing of nitrogen fertiliser and differing cultivars.

Considered to conserve moisture until grain fill, wide rows of up to 60cm — generally not be used in a normal production system — were investigated as part of the research.

Field trials at Merredin under controlled climate conditions showed that while wider rows used water slower, the offset was a greater loss through increased evaporation and often a yield penalty.

“Wide row spacings (greater than 50cm) offer wheat farmers practical benefits such as increased sowing speeds, timeliness of sowing and reduced tractor horsepower requirement, but it often comes as a consequence of reduced grain yield, particularly in those one-in-five years where farmers make a lot of their money, ” Hayden said.

However, there are some situations in which wide rows can prove beneficial.

“On certain soils where the soil is shallow and you’ve grown a lot of biomass up to anthesis and then you have a drought, if all those stars align then wide rows can be beneficial, ” Hayden said.

Victorian variety Silverstar as well as Wyalkatchem, Westonia and Halberd were used throughout the trial, but evidence suggested longer-season cultivars performed better on wide rows.

“If you’ve got that extra moisture at the end of the season and the crop finishes before it can use it, it doesn’t make use of it, ” Hayden said.

“If a crop grows a bit longer then it uses that extra moisture and puts it into grain and bigger grain sizes.

“In my experiments, I found that the cultivars that tend to be a bit longer seasoned — not by much, maybe only by seven days — they were better in the wider rows than what the shorter-season varieties were.

“So if farmers do want to go wider they should probably be looking at or thinking about which varieties are suitable.”

But he said the challenge lay in developing suitable cultivars.

“We need more research into that, ” Hayden said.

“At the moment, from what I understand, a lot of breeding companies use very narrow row spacings in their selection process, which isn’t actually what most farmers use in the field.

“There might be certain characteristics in a variety that make it better in wider rows, but because they’re not selected under that production system in the breeding programs they don’t get released.

“I would like to see varieties selected in the same production systems as they are widely grown.”

Longer-season cultivars could also have superior performance as the effects of climate change are realised.

Hayden used climate data from a model developed by the Department of Agriculture and Food WA to assess what might happen to flowering times in the 30 years following 2036.

“What I found there was because varieties develop in response to temperature, the hotter it is the quicker they reach maturity, ” he said. “I used two varieties — a long-season and a short season — in my modelling, but the short-season variety was too short and the long-season one did far better.

“So what could happen, going forward, is varieties will need to be longer-season because they’ll mature faster with the heat.”