The influence that crop row width has on productivity and profitability is being examined by BCG as part of the GRDC-funded stubble initiative.
The widespread adoption of stubble retained cropping systems across the Wimmera and Mallee over the last two decades has motivated many growers to widen crop rows from the traditional 7” (18cm) or 9” (22.5cm) out to 12” (30.5cm), 15” (38cm) or even 30” (76cm).
The predominant reason for doing this was to overcome stubble handling issues at sowing time, thereby improving efficiencies and eliminating problems such as seeder blockages when sowing into stubble. Widened rows also made inter-row sowing easier and improved pre-emergent herbicide safety.
However, as retained stubble farming systems have evolved along with machinery improvements, including disc systems and better GPS guidance, many growers have questioned the value of wider rows with higher yields, better weed competition and less soil water evaporation key benefits of narrower row spacings.
In 2015 BCG sowed a number of field trials on a range of row spacing to compare weed growth and crop performance. The results indicated that yields were improved when row spacings were kept below 30.5cm (12 inch).
A trial established at Jil Jil (north of Birchip) saw weeds establish faster where row spacings were wider (38cm, 15 inch), while the establishment of Mace wheat was better in plots sown on 22.5 (9 inch) or 30.5 (12 inch) rows.
In this trial yields were significantly higher under the narrow row spacing, with the 38cm (15 inch) row spacing yielding 0.13t/ha less than wheat sown at the other two spacings. (Angel K., 2015).
Another trial conducted by BCG at Berriwillock in 2015 measured the performance of Mace and Trojan wheat sown at three different row spacings – 22.5cm (9 inch), 30.5cm (12 inch) and 38cm (15 inch). A wheat variety trial at this site was also sown to two different spacings (22.5cm and 38cm) to see if different wheat varieties behaved differently at different row spacings.
The findings from these trials again showed improved yields at narrow row spacings over their wider counterparts. There was no interaction between wheat variety and row spacing. (Browne C., 2015)
While the results from these trials showed that yields can be improved by decreasing the width of crop rows, in a commercial setting this may not equate to improved profitability.
Investigations being carried out by BCG and its stubble initiative project partners Irrigated Cropping Council, Southern Farming Systems and the Victorian No Till Farmers Association, has revealed that decisions pertaining to row spacing selection go beyond potential crop yield.
According to Victoria No Till Farmers Association, “the best row spacing is the one that suits your individual farming system.” Key factors influencing the decision include sowing logistics and cost, with more sowing implements (discs or tynes) on the seeder adding to set-up and maintenance costs and reduced sowing speeds.
The optimum row spacing will change with crop types, seasons, yield environments, weed burdens, soil type and, of course, machinery.
Nevertheless, in stubble retained systems, careful planning and management is required to understand residue flow, seed placement, pests, disease management and herbicide efficacy (including soil throw and incorporation of volatile pre-emergent herbicides such as trifluralin) in order to support decisions about the most suitable row spacing.
Further research into row width in a stubble retained farming system will be carried out by BCG this year.
More information on row width, including 2014 and 2015 research results, is available at: https://thestubbleproject.wordpress.com
