In grain cultivation, working cost-efficiently is crucial. This starts with sowing, because seed is a considerable cost item. By better aligning the sowing density, savings can be made and the twigging potential of wheat varieties is better utilised. Hybrids are known to be strong chairs, but classic varieties also surprise sometimes. Based on these insights, a trial was set up to investigate how far the sowing density can be reduced without yield loss or increased risk of alloying.
Reason for the trial
- Practical experience and foreign studies show that plants grow better at a lower sowing density, which leads to more ears per plant. In addition to a possible saving on seed, a lower seed density can also reduce the risk of alloying. This can therefore potentially reduce the use of culm shorteners.
- The goal of a lower sowing density is not to achieve higher yields. It is about optimization, where a stable yield can still be achieved with less input. This is to improve the net financial profit of the plot at the end of the ride.
These insights are the reason for a trial design to investigate the extent to which the sowing density can be reduced by relying on the trellising capacity with stable yield and a limited risk of alloying.
Two wheat varieties tested
Two wheat varieties were included for this trial. Both varieties were sown at 100 and 200 kg/ha on polder soil. Post-emergence counts resulted in an average of 191 plants/m² at the low sowing density and 330 plants/m² at the high sowing density. Figure 1 shows an overview of the experimental design.
Figure 1: Overview map of the trial and NDVI values on 24/04/2025 (values 0-1, with 1 as the maximum NDVI value)
Drone flights map crop development and yield
The trial was followed up by regular drone flights. Based on these images, the greenness index (NDVI) was determined, which was used to map the crop development from emergence to ripening:
- The high sowing density of Variety A has the highest greenness throughout the season, until shortly before ripening.
- The lower sowing densities have a lower greenness throughout the season, but from April the difference between the strips becomes smaller.
Alloy
The drone image from July 17, 2025 below (RGB photo) shows the alloy very well. Especially the high sowing density of Variety A, which had the highest greenness during the season, shows strong alloy.
Revenue map
The strip width was matched to that of the combine harvester, equipped with automatic yield mapping. Each dot on the map below is a yield measurement. In the strips with the high sowing density of Variety A, it is clear that the yield is lower (light green balls) on the left side due to the alloy we saw on the drone image.
The differences in yield are just a little more pronounced on the graph below:
- The lower yield due to alloy in the high sowing density of Variety A on the left side of the field is obvious.
- In addition, the high sowing density of Variety B achieves the highest yield over almost the entire length of the trial, followed by the low sowing density of Variety A.
- The low sowing density of Variety B fluctuates greatly in yield, from 16.8 to 12.9 tonnes per ha. Although this strip in the field lies between the two high sowing densities, this variation is only present at the low sowing density.
- Yield map of the trial and yield (tons/ha) compared to the distance to the headland
Weighbridge vs yield map
The farmer also measured the yield per strip with the weighbridge. Compared to the yield map, the yields per hectare are lower here. It is striking that both low sowing densities achieve a similar yield, while the yield map shows a higher yield for the low sowing density of Variety A.
Conclusions
- Variety A shows alloy at a high sowing density and probably shows a lower yield because of this.
- Variety B has the highest yield at a high sowing density, but at a low sowing density the variation is too great to draw a conclusion.
The yield differences between a high and low seeding density are limited, while the costs are lower with a lower seeding density and the risk of alloying is higher with too high a seeding density.
So don't sow at a sowing density that is too high, but tune in to the twigging capacity of the chosen variety. For varieties with a weaker stool capacity, some caution is still needed. This not only saves on seed costs, but also reduces the risk of alloying.
More information?
Bram Vervisch (Inagro): bram.vervisch@inagro.be
Sarah Bossuyt (Inagro): sarah.bossuyt@inagro.be