Row Spacing Options for HRZ Farming Systems throughout SW Victoria

| Date: 20 Jun 2008

Rohan Wardle1 and Mark Steele2,
Southern Farming Systems1, Mininera Research Site & La Trobe University2, Bundoora Campus

Take Home Messages:
• In the season of 2007, wider row spacings (300mm vs 200mm) did significantly (P<0.01) impact on yield (5.31t/ha vs 4.98t/ha) when averaged across three wheat maturities in the higher rainfall zone of western Victoria , suggesting that the benefits of wider row sowing for crop residue management practices are coming at a significant financial cost ($100/ha+, using current prices), see Table 1.
• Cultivar performance does also appear to be as significantly (P<0.01) important as row spacing width, suggesting that variety choice for undertaking wider row sowing needs to be a considered priority. Kellalac wheat, averaged across both 200mm and 300mm row spacings widths yielded 4.61t/ha, compared with Bolac; 5.16t/ha and Beaufort; 5.72t/ha.
• Tiller counts were also significantly less (P<0.01) when moving to the wider row spacing widths. Beaufort had significantly (P<0.01) fewer tillers/m2 than did Kellalac, which in turn had significantly fewer tillers than did Bolac. When the row spacing increased to 300mm, both Kellalac and Bolac had a significant reduction in tillers, while counts for Beaufort did not drop significantly. Overall, Kellalac was least able to handle the increase in row spacing width for tiller counts within this trial.
• Row spacings widths of 200mm with nitrogen applied at GS00 & GS31 trended (P=0.06) toward higher yields (5.30 & 5.33t/ha) when compared to row spacing widths of 300mm with nitrogen applied at GS00 (5.09t/ha) & GS31 (4.88t/ha), suggesting that the timing of nitrogen for wider treatments may need to be a separate consideration to achieve adequate biomass productivity for yield maximisation within this newly adopted farming system.

Alternate stubble management practices to burning in the HRZ of Victoria are now being recognised as both beneficial to soil health and crop performance. Various mechanical and crop husbandry techniques have been implemented in recent years to maximise seeding timeliness and efficiency, whilst still maintaining a seedbed adaptable to the variable climatic influences. Current research on row spacing widths has not been conclusive in the higher rainfall zones throughout SE Australia, especially now with recent acquisitions of RTK guidance systems and farmers aiming to achieve inter-row seeding, lessening the need to manipulate crop residues post harvest and prior to seeding operations for the new season program.

Yield variance under alternate row spacing, nitrogen and variety treatments
In 2007, a completely randomised block design field trial with four replicates was undertaken at the Southern Farming Systems Mininera research site to evaluate the yield variance across two row spacings (200mm & 300mm), three wheat maturities (Kellalac (L), Bolac (ML) & Beaufort (M)) and two nitrogen timings (GS00 & GS31). Standard farmer practice across the south west of Victoria has been the adoption of in-crop nitrogen timings (GS31), however consideration for variety, widening row spacings and the resultant interaction has not been fully understood. A typical farmer input scenario may see Kellalac sown at 200mm row spacings widths, with nitrogen applied at GS31, yielding 4.64t/ha, but when compared to Beaufort sown at 300mm with nitrogen applied up front (GS00), there was an average yield deficit of 0.98t/ha (Table 1.). This research has also shown that when using wider row spacings, tiller counts are significantly (P<0.01) more per square metre in the narrow row spacing treatments for the two milling wheats, but not so for the feed grain wheat Beaufort. Heads per square metre were significantly (P<0.01) greater in all narrow spacings across all varieties (447hpsm vs 385hpsm, LSD = 31hpsm) when compared to wider row treatments. Bolac had significantly (P<0.01) more hpsm (457hpsm) than Kellalac (383hpsm) or Beaufort (407hpsm) LSD = 38hpsm, but this did not represent a yield benefit over the feed wheat variety as grain size (thousand grain weights) were significantly (P<0.01) more within the red wheat treatments (38.06g for Beaufort vs 33.39g for Bolac and 33.41g for Kellalac). Protein percentages were significantly (P<0.01) less in Beaufort (11.64%) when also compared to Bolac (13.56%) and Kellalac (13.13%) LSD = 0.35%, showing an inherent expression of lower protein set down in the feed type grain. Screening percentages were significantly less in Bolac (0.73%) than in Kellalac (1.26%) or Beaufort (1.3%), LSD = 0.23%, showing that Bolac has a strong tendency to achieve the more desirable high protein and low crop screening percentage outputs. Later applied Nitrogen also expressed a significantly higher protein percentage as an average across all varieties (12.57% vs 12.98%) LSD = 0.28%, as would be expected when applied within the reproductive phase of the growing crop. Later applied nitrogen did also show a significant (P<0.01) benefit in test weigh across all varieties (75.00kg/hl vs 75.46kg/hl) LSD = 0.39.

Table 1. System interactions across Wheat Variety, Row Spacing Width and Timing of Nitrogen on Crop Output, when considering stubble retention and inter-row seeding practices in the HRZ of SW Victoria, SFS Research Site (Mininera) 2007.

Crop Interactions
Variety t/ha
Row Space
V x N t/ha
V x RS
RS x N
 V x RS RS x N x V
Row Spacing
Variety x Nitrogen Timing
Kellalac GS00N
Kellalac GS31N
Bolac GS000N
Bolac GS31N
Beaufort GS00N
Beaufort GS31N
Variety x Row Spacing
Kellalac 200mm
Bolac 200mm
Beaufort 200mm
Kellalac 300mm
Bolac 300m
Beaufort 300mm
4.81    4.64
5.21    5.51
5.90    5.84
4.73    4.26
4.92    4.85
5.62    5.53
Row Spacing x Nitrogen
200mm GS00N
200mm GS31N
300mm GS00N
300mm GS31N
LSD (0.01)
LSD (0.05)
 NS         NS

Wholly Protected Data. Means followed by the same letter do not significantly differ (P=0.01, LSD), NS = Not Significant.

Greenseeker™ (NDVI) was one tool used on fortnightly timings up to GS70 to determine if a regression exists with canopy greenness at flowering, yield outputs and the effects of row spacing widths. At this stage, there was no interaction within this trial to suggest any likely association between these observations.

For research purposes, this trial was not sprayed with in-crop herbicides or fungicides to help manipulate and strategically determine influences on crop performance when placed in a more competitive environment. Further research is currently being considered for 2008 to integrate phosphorus rate and nitrogen rate/timing strategies across the two row spacing widths within one wheat variety. Date of sowing does have known influence of yield outcomes, thus would not be included as an additional treatment at this stage.

Trial Observations
• Within this data set, there was no significant difference (P=0.06) between narrow row spacings with nitrogen applied up front or in crop, compared with wider row spacing and nitrogen applied, suggesting an important nitrogen timing/management decision process to be applied with changing row spacing widths and soil nitrogen reserves at time of sowing.
o Soil nitrogen at planting was 31mg/kg nitrate in a dry February, taken to 60cm. The trial was seeded with MAP at 90kg/ha. Urea was either applied at GS00 or GS31 at a rate of 33.6kgN/ha. Dose rate within this trial may have achieved a different outcome within the current treatment list, now knowing the favorable crop finish for the Mininera district in 2007.
• Disease presence and severity did not appear to be significantly worse in the narrower row spacing treatments within the susceptible cultivar Kellalac. Both stripe and leaf rust presence and severity were assessed at GS70, 10 days after rainfall
• Greenseeker ™ did not appear to show a strong relationship with previous NDVI assessments, r2<0.47, making future use of this tool for undertaking analysis of wider row spacing research somewhat difficult without ground truthing.
• Weed incidence was not significant across this site, thus could not be concluded to have any effect on crop performance across row spacing widths or varieties within this trial.
• This trial has not considered any costs savings from not having the need to manipulate crop residues; be able to sow at greater speeds using wider row spacings; or the reduction in horse power pulling fewer tines through the ground at seeding.

When assessing most of the systems interactions across this trial, Table 1. shows significant data to suggest the impact that variety, row spacing widths and nitrogen timing do have on crop yield outputs. Unfortunately, the full system interaction, such as Kellalac at 300mm row spacings, with nitrogen applied at GS31 did not significantly show a yield difference when comparing to nitrogen applied at GS00 for the same variety and row spacing.

For similar interactions within barley agronomy trials, the research does appear to show different outputs to row spacing interactions. Barley variety row spacing trials were undertaken within the SFS research program at two research sites in 2007, with results available upon release at each Branch results session to be held in March 2008.

Rohan Wardle
Research & Extension Agronomist
& Trials Programme Coordinator
Southern Farming Systems
Suite 3/318 Pakington St (PO Box 8047)
Newtown VIC 3220
M: 0438 343079 | P: 03 5229 0566 | F: 03 5229 4426
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