INCREASING row width from the once-standard 18 centimetres to wider row spacings, on average results in lower wheat, barley and canola yields with losses generally greater the higher yielding potential the crops have.
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A recent report that examined 89 southern Australia winter crop row spacing experiments Row spacing of winter crops in broad scale agriculture in southern Australia concluded it was generally better, where possible, to sow in narrow rows than wide ones.
Long term data from Wagga Wagga (high rainfall) and Condobolin (low rainfall) was an important source for the analysis.
Authors of the report were adjunct professor at the Faculty of Science, School of Agricultural and Wine Sciences, Charles Sturt University, Brendan Scott; former Department of Primary Industries' senior research agronomist at Farming Systems, Peter Martin, who now runs a consultancy business in Queensland, and development officer for Western Australia Department of Agriculture and Food Glen Riethmuller.
Toni Nugent, Graham Centre for Agricultural Innovation and Catriona Nicholls, Hot Tin Roof Communications, edited the document.
The report noted farmers adopted wider rows (above 18 cm) to improve flow of sowing machinery through stubble.
Other wide row advantages included reduced fuel and faster sowing.
In wide row crops major problems included more competition from weeds, increased risk of seedling damage from close fertiliser placement and often reduced plant populations, even when fertiliser and seed were placed separately.
The rate of yield loss with row widening increased as site yield increased, although there was considerable variability between experiments.
Generally at yields below 700 kilograms a hectare, widening rows beyond 18cm, increased grain yield.
For example, at yields of 500kg/ha, doubling the row space to 36cm increased yield to 520kg/ha.
However, at yields of two tonnes a hectare widening rows to 36cm reduced yield to 1.86t/ha and at 4kg/ha yield was reduced to 3.64t/ha.
However the challenge of high stubble loads is more frequent in higher rainfall areas with higher grain yields, the conditions where reductions in grain yields from wide rows are likely to be greatest.
Although only 18 barley experiments were identified, the rate of yield change with changes in row spacing was similar to wheat.
At yields of greater than 1.1t/ha at 18cm row spacing, widening rows decreased yield.
Canola yield declined as row spacing increased (in 13 NSW experiments) with the rate of decline similar to wheat.
Data from lupin research (WA 29, NSW 10 experiments) showed more variable row spacing response.
Commonly in WA 18 to 30cm rows yielded less than 42 to 60cm, but declined when 84 to 100cm.
NSW data indicated yields decreased with wider rows.
Agronomic practices that commonly produced highest yield at 18cm also produced the highest yield at 36cm rows, for example weed control, sowing time, cultivar and fertiliser management.
The report noted that "paired or ribbon row" sowing appeared to offer some scope in mitigating the loss of grain yield as row space increased.
Results from the review recommended farmers avoid where possible increasing row spacings or at least keep them as narrow as possible.
Next week. Lower sowing rates can save big dollars and result in top winter pasture establishment.
Bob Freebairn is an agricultural consultant based at Coonabarabran. Email robert.freebairn@bigpond.com or contact (0428) 752 149.
