Dutch farmer starts with variable sowing of beets

Arable farm Cerfontaine in South Limburg (The Netherlands) will sow variable sugar beet this year. This means a variable sowing distance. Where the soil is less productive, i.e. has less potential, sowing is done more closely. Elsewhere, the normal sowing distance of 18 centimeters is maintained. “The idea behind this”, says NPPL participant Daniël Cerfontaine, “is that on poorer soil more small beets together yield more net tons than large beets that need more space due to good nutrition. From the normal distance between the seeds, we locally go back to 15 to 16 centimeters in the poorer places.” NPPL is the National Experimental Garden for Precision Farming.

Yield maps and satellite imagery

The task map from which the beet seeder is controlled is based on multi-year wheat yield maps and historical satellite maps of crop development on the two fields – one of 6.5 hectares, one of 21 hectares – on which Cerfontaine is conducting this year’s experiment. “These satellite maps show the development of different crops over the years. What we see is that the variation development of the crop masses corresponds reasonably well with what we see in wheat yield maps.”

Returns unclear

Cerfontaine will sow the experimental beet plots in early May, more than a month later than he would have liked. He will observe the effect of the measure with the beet harvester with yield measurement, of which the arable farm/contractor has two. In the first instance, the kilo yield is determined on a spot-by-spot basis. In a retrospective analysis, it should become clear to what extent there is a relationship with the variation in the sowing distance. And whether there is an improvement compared to normal sowing. Differences in sugar content between small and large beets are not considered. Initially, the trial provides a yield map of where the most tons of beet grow in the plots. Such a map does not necessarily have to overlap completely with a sugar yield map, Cerfontaine acknowledges, although he assumes that at first.

Spray less

During this 2023 growing season, Cerfontaine will also monitor the beet plots on biomass maps.

When it comes to the efficiency of this and other VRA applications (VRA = variable rate application), Daniel Cerfontaine is hesitant. In the sense that he does not yet see a financial return from it for the time being. “Seven years ago we started variable spraying. If I’m going to calculate the hours of preparations, equipment and making cards, then I can say that it doesn’t make any money. At most, we spray a little less.”

Difficult to draw firm conclusions

But in any case it is difficult to estimate what a precision measure such as variable beet sowing yields. For example, what is your reference year on a particular plot. There are many more causes for variation in what a field yields from one year to the next. It will be sowing at least a month later than normal. Besides, we won’t be back here for another four years with sugar beets. By then you will have other varieties and perhaps better methods of fighting disease. “All factors that make pure comparison very complicated to make firm statements about the effect of variable beet sowing on our soil.”

None of this has stopped Cerfontaine from continuing these kinds of experiments. For the longer term, he is convinced that this is the way forward for agriculture. “That is why we will now continue to gain experience with this. We will see later what it brings us in the end.”