Grain growers are many things, but they might soon have to add architect to their long list of professional responsibilities.
New research has suggested that controlling the architecture, or spatial geometry of grain crops, can have a positive impact on yield.
This research, from Western Australias northern wheatbelt, has discovered a positive relationship between uniform canola and lupin plant spacings and yield.
WA Department of Primary Industries and Regional Development (DPIRD) research officer Martin Harries has been investigating the impact of plant density and spatial placement, particularly on intra-crop plant competition, plant water use efficiency, and plant biomass which all ultimately impact on yield.
Mr Harries found spacing plants more evenly could see yield improvements of up to 17 per cent.
Spatial geometry studies
Plant-density studies are commonly done throughout Australias grain-growing regions to provide growers with a guide as to the most profitable number of plants per square metre.
However, until now, there has been little available data on plant geometry or spatial heterogeneity.
Spacing plants more evenly could see yield improvements of up to 17 per cent
In fact, until 2018, only two studies on geometric uniformity for commercial canola crops had been undertaken, the first in Canada, which concluded in 2012, and the second at Wongan Hills, WA, in 2016.
The Canadian study found yield improvements of up to 32 per cent, when comparing even plant geometry with uneven plant geometry.
In Wongan Hills in 2016, while the results were not quite as clear cut, there was a yield increase of six per cent in the evenly spaced canola treatment where plant density was 20 plants/m. This trial showed the same results as the earlier studies in Canada where the greatest yield increases occurred at 40 plants/m or less.
Last year, Harries again tested the theory that uniform plant spacings at these lower-density rates yielded higher than those crops planted in an ad hoc fashion.
His GRDC-invested trials in Geraldton, WA, in deep loamy sand, included one lupin and one canola trial, with 10m wide x 2m long plots, at plant densities of 80, 40, 20, 10 and 5 plants/m.
At each plant density the plants in the plots were either evenly or unevenly spaced. To ensure the plant spacings in his trial plots were positioned accurately, Harries and his team hand-thinned the uneven plots to mirror what was found in commercial paddocks, with the even plots thinned into a diamond, or grid pattern, allowing each plant maximum soil area.
For canola, the evenly spaced treatments at plant densities of five, 10 and 20 plant/m achieved yield gains (of 15, 8 and 17 per cent respectively) over the unevenly spaced treatments.
Likewise, the lupins yielded 7 per cent better in the even spacing treatment at a plant density of 20 plants/m.
Mr Harries also undertook a survey of 42 paddocks in WAs northern, central and eastern wheatbelt, assessing crop uniformity. He says there was a substantial amount of variability in plant distribution from commercial seeders, which was greater as the plant density decreased.
He says these trials were undertaken to get an idea of the value of improving the distribution of plants from what is currently achieved with conventional seeding equipment.
Obviously hand-thinning is not applicable on a broadacre scale, but there are new seeding technologies that are being assessed in separate projects, Mr Harries says.
Precision planting technology
A GRDC-invested research project in the southern and western regions, managed by the University of Adelaide, has been trialling precision planting technology, comparing the yield results with those crops planted by conventional air seeders.
Ag Consulting Co consultant Stefan Schmitt, based on South Australias Yorke Peninsula, has been managing the trials on behalf of the University of Adelaide, and says the trials were examining anecdotal observations made by growers in Victoria who had adapted precision seeding equipment, and had demonstrated reasonable yield gains were possible with evenly planted crops.
The small plot trials, run at Hart, SA, in conjunction with the Hart Field Site Group, and at Birchip, Victoria, together with the Birchip Cropping Group, were both planted to lentils and canola in 2018.
For both sites, the treatments included six different plant densities, two row spacings (23 and 30 centimetres), and the two different seeding machines (precision versus conventional).
Mr Schmitt says precision seeders are common in the US and Canada and used for corn and soybean planting where the cost of hybridised seed is high and plant-to-plant spacing is a key lever in achieving maximum yield.
Early adopters are adapting the technology by modifying their own seed plates to suit our Australian winter crops.
These trials will give useful data on the capacity of precision planters to improve seed-to-seed spacing in lentils, beans and canola, and see if this translates to a yield improvement, Mr Schmitt says.
Precision vacuum planters work by sucking the seed onto a computer-controlled rotating plate, and each seed is knocked off the plate by a knock off wheel and singulator. This results in the seed being dropped into the soil one at a time, or singulated
The control system manipulates the rotating speed of the plate, which is dependent on the forward speed of the planter and the desired planting population
At the end of the three years of these trials we will know if yield gains are achievable or if seed savings can be made, Mr Schmitt says.
Ultimately, we want to discover if this technology is worth the investment.
These trials will give useful data on the capacity of precision planters to improve seed-to-seed spacing in lentils, beans and canola, and see if this translates to a yield improvement
First year trial results have been analysed by University of Adelaides Associate Professor Glenn McDonald, who says poor seasonal conditions in Victoria saw no clear yield difference between the precision and the conventional planted plots in Birchip.
Yields on all treatments were very low because of a very low-decile rainfall year, with the only yield difference occurring as a result of increased plant density he says.
Across all treatments, the average canola yield was 900 kilograms per hectare, and the lentil average was 350kg/ha.
There was no difference at Birchip between the narrow and wide spacings.
At Hart, SA, where it was also a low-rainfall year (with 160 millimetres received for the growing season), Associate Professor McDonald says there was a 10 per cent yield improvement in canola in the precision seeded narrow row treatment, when compared with the conventional cone seeder.
Average yields at the Hart site for canola were 1.38t/ha and for lentils were 1.29t/ha.
There was no statistical difference in yield comparing the different seeding methods on the wide rows.
In the lentil trial, average yields were about 5 per cent higher when sown with the precision seeder compared with the conventional cone seeder
Both Associate Professor McDonald and Mr Schmitt hope better season conditions in 2019 and 2020 will allow for clearer observations from these three-year trials.
Paddock-scale precision planter trials are also occurring in WAs central wheatbelt, run by the WA No Till Farmers Association as part of this investment. Results on these trials will be available at the end of the year.
A GRDC survey of precision-planted crops across 200 paddocks throughout the western and southern regions is assessing crop establishment, depth and uniformity of crops, and in 2019, will collate relevant machinery, soil and plant information, such as seeding systems, soil type, stubble loads, soil conditions before and after sowing, seed germination rate, sowing rate, fertiliser rate and placement.
These surveys will help inform future GRDC invested research in this project.
GRDC Research Codes DAW00227