| Researcher(s) |
Linda Bailey |
|---|---|
| Year(s) | 2022 |
| Contributor | Northern Grower Alliance |
| Trial location(s) |
Pittsworth, QLD
|
To evaluate the impact of sorghum row spacing and plant population on fallow efficiency
This trial was designed to investigate the impact of sorghum row spacing and plant population on fallow efficiency. MR Bazley sorghum was sown In October 2021 at ~3 kg/ha using a single disc planter on a 50 cm row spacing (grower’s standard practice).
Crop establishment was assessed 35 days after planting (35 DAP1) with ~11 plants/m2 in the grower’s standard practice. The target plant populations and configurations were achieved in the comparison treatments. Treatment 2 also had a population of ~11 plants/m2 on 25 cm row spacing with treatment 3 having ~21 plants/m2 on 25 cm row spacing. Treatment 3 had an equivalent number of sorghum plants/ m row as treatment 1 but twice the number of rows.
There was a total of ~590 mm in-crop rainfall with ~200 mm received in the final 3 weeks before harvest. The sorghum was harvested at 147 DAP1 with the grower standard configuration yielding ~6.5t/ha.
There was a significant yield increase (+0.3 t/ha) from increased plant population (treatment 3) compared to either treatment 1 or 2. There was no significant impact on yield from narrowing row spacing.
An EM38 survey to assess the ‘establishment’ crop effect on soil water was conducted 21 days after harvest. During that period ~180 mm of rain was recorded. The grower’s standard had significantly higher EM38 readings (increased soil moisture) than both the 25 cm row configurations at both shallow and medium depths (37.5 and 75 cm). Image analysis was used to evaluate the level of groundcover. Treatment 3 (25 cm row spacing 21 plants/m2) had significantly higher levels of groundcover than the grower’s standard with treatment 2 not significantly different to either. All treatments had ~2.6-2.8 t/ha of stubble dry matter.
The trial was expected to be planted to sorghum as the ‘evaluation’ crop in 2022/23, however unexpectedly barley was planted in late June. The change in planting intention was only discovered in early September. Consequently, the end of fallow EM38 survey was not possible and a barley establishment count could not be conducted.
There was no significant difference in barley NDVI (crop biomass) or yield between the sorghum row spacing and plant population treatments. The grower’s standard practice yielded ~5.9 t/ha.
In this situation, an increased plant population in the establishment year provided a significant yield benefit with no apparent impact from the narrow row spacing alone. Insufficient data was able to be captured to confidently assess the impact of row spacing and plant population on fallow efficiency. Treatment 2 (25 cm row spacing and 11 plants/m2) produced an equivalent yield to the grower’s standard in the establishment year and despite ~380 mm of rainfall in the last 3 weeks of grain ripening and the first 3 weeks of fallow, was still significantly drier at the shallow and medium depth assessments. The narrower row spacings (treatments 2 and 3) extracted more water from the shallow and medium soil depths and is likely to be due to individual plants being able to utilise more water in the interrow. There was no indication of crop biomass or yield differences in the barley (evaluation crop), however the absence of comprehensive EM data in the fallow and barley establishment counts prevents analysis of the causal factors.
The results in this trial are similar to other trials in this project. Differences in yield due to row spacing or plant population in the establishment crop are frequently observed, however differences in the fallow efficiency or following crop yields have been minor.
| Lead research organisation |
Northern Grower Alliance |
|---|---|
| Host research organisation | N/A |
| Trial funding source | GRDC NGA2009-002RTX |
| Related program | N/A |
| Acknowledgments | N/A |
| Other trial partners | Not specified |
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