Autumn boning of rapeseed and winter cereals
Soon it will be that time again - with the autumn season N-Sensor farmers start the season again. The fall scan of winter canola and cereals has become a fixture in the working calendar over the past few years.
If you
- Adjust your spring N fertilization to the differently developed subplots of a field,
- measure the absolute N fertilization level for the first N application not according to your gut feeling but according to the actual nitrogen uptake of your plants, and
- you want to apply the first N fertilizer as sparingly as possible in view of the Fertilizer Ordinance and the associated N fertilizer quantity limits, but also in a way that promotes the crop,
then only the autumn scan with the YARA N-Sensor® on your winter rape and winter cereal areas is the means of choice. The YARA N-Sensor® not only provides you with high-resolution information.
Above all, it is the only sensor in the world that tells you exactly how many kilograms of nitrogen are actually in the stocks.
Only with this information can you agronomically derive the amount of the first N application. Everything else, such as the use of Nmin studies, is intelligent guesswork. And that we absolutely must get to the subplots is shown by the huge variations from field to field AND within plots - in any given year at almost any site. It is useless to waste more time with endless discussions about the DVO, you have to get into action as a farmer!
What does this mean for fertilization - example canola
N uptake in canola varies by an average of 60 to 90 kg N uptake/ha on uniformly managed plots.
This means that in the case of rapeseed, we are off by 30 to 45 kg N/ha with constant fertilization!
Graph 1 summarizes the clear data from the last 5 years.
![[Translate to Englisch:] Grafik 1: N-Aufnahme von Raps nach Herbstscan 2016 - 2020](/fileadmin/_processed_/8/d/csm_N-Aufnahme_von_RAPS_nach_Herbstscan_6b789f14f9.png "[Translate to Englisch:] Grafik 1: N-Aufnahme von Raps nach Herbstscan 2016 - 2020")
The target for pre-winter development is generally considered to be an N uptake of 70 to 90 kg/ha. These were regularly achieved in the past years. The mean minimum (orange) and maximum (green) N uptakes in graph 1, however, show very clearly how heterogeneously the subplots are developed within the fields. These differences have to be taken into account for a demand-oriented N-supply during fertilization.
The following table shows an example of how the first nitrogen application can be adapted to this heterogeneity:
![[Translate to Englisch:] Sollwert N-Aufnahme Raps zu N1](/fileadmin/_processed_/b/e/csm_Sollwert_N-Aufnahme_Raps_zu_N1_421efb2d5e.png "[Translate to Englisch:] Sollwert N-Aufnahme Raps zu N1")
The target value for N uptake corresponds to the sum of nitrogen already taken up plus mineral N fertilization. The possible yield expectation does not initially play a role in a split application strategy. Rather, this is then taken into account in the second N application.
Example winter barley
In barley, we lay a good foundation for high and robust yields with an autumn N uptake of 20 to 30 kg N/ha and in wheat of 15 to 25 kg N/ha. A closer look at the fields reveals average N uptake differences of around 30 kg N/ha in winter barley and around 20 kg N/ha in winter wheat.
That's about a two to three week head start on development in the spring, or just two to three weeks of missing growing season.
![[Translate to Englisch:] Grafik 2: N-Aufnahme von Wintergerste nach Herbstscan 2016 bis 2020](/fileadmin/user_upload/Blog/2021/N-Aufnahme_von_WINTERGERSTE_nach_Herbstscan.png "[Translate to Englisch:] Grafik 2: N-Aufnahme von Wintergerste nach Herbstscan 2016 bis 2020")
Only with greatly increased N application will the poorly developed subplots come close to the yield potential of the well-developed subplots. And the sooner you react to this, the better.
The following table shows again exemplarily how one should dose the 1st N-application adapted in this situation with a winter barley. The procedure for winter wheat is analogous.
![[Translate to Englisch:] Regelfaktor (kg N-Düngung/kg N-Aufnahme)](/fileadmin/_processed_/1/3/csm_Regelfaktor_ec060adba1.png "[Translate to Englisch:] Regelfaktor (kg N-Düngung/kg N-Aufnahme)")
Heterogeneity is found on all surfaces
It is often claimed that "...this is only worthwhile in large areas, in small fields the differences are not so great."
On the one hand, it is true that the variation in N uptake increases with increasing field size. This can be read well in the example of the 2017 fall scan of canola. The heterogeneity was on plots
- smaller 10 ha -> 68 kg N/ha
- larger 40 ha -> 122 kg N/ha.
![[Translate to Englisch:] N-Aufnahme Winterraps nach Flächenklassen 2017](/fileadmin/_processed_/d/f/csm_N-Aufnahme_Winterraps_nach_Fla__chenklassen_2017_3_da0196f682.png "[Translate to Englisch:] N-Aufnahme Winterraps nach Flächenklassen 2017")
On the other hand, the usefulness of the scan also becomes clear very quickly on "smaller" fields if one considers the corresponding N fertilizer quantities.
Calculation example for fields up to 10 ha:
![[Translate to Englisch:] Sollwert N-Aufnahme](/fileadmin/_processed_/d/7/csm_Sollwert_N-Aufnahme_41caa85e19.png "[Translate to Englisch:] Sollwert N-Aufnahme")
Thus, an average N fertilization of 81 kg N/ha would not be optimal in the better or weaker developed subplots and would not lead to the optimum yield.
Fall scan is worth it!
Determining the stand heterogeneity of your winter crops and adjusting N fertilization makes sense. And it makes sense in more ways than one:
Agronomically: because stands are just not the same. Different subplots have different N optima and thus different N needs. These need to be met in order to maintain the chance of optimum yields.
Economically: Because fertilizer is expensive, may be in short supply, and should therefore be used with the highest possible efficiency.
Legal: The Fertilizer Ordinance sets hard limits on application rates. In many fields, the N amounts are NOT sufficient anymore, for achieving the optimal yield. With a N-application adapted to the small-scale plant demand, you can try to compensate the probable yield decreases as good as possible.
Therefore, the earlier you start with demand-based crop management, the greater your chances of success.
