Modern oilseed rape varieties are nearly 30% more Nitrogen efficient than the highest yielders from just a few years ago, a series of trials in Germany has shown.
With Nitrogen utilisation increasingly in the spotlight, the trials highlight a number of factors contribute to a plant’s ability to make better use of nutrients and cannot be tied to a specific gene.
“The highest yielding oilseed varieties are also the ones that have the best Nitrogen Utilisation Efficiency (NUE),” explains DSV’s Simon Kroeger.
“Such varieties are characterised by deep rooting systems which enable them to take up N more effectively. A strong deep taproot together with long side branches to maximise nutrient and water supply are key.
“But an ability to cope with abiotic stresses such as drought more effectively and in-built resistance to a broad range of diseases are also important.
“Research shows it’s a plant’s overall yield potential, resilience and the strength of its physical characteristics that make it able to use N more efficiently rather than it be any one specific feature of a variety.”
“Varieties that produce consistently high yields in varying climatic conditions across number of years are unequivocally the ones with the best Nitrogen efficiency.
“In particular, the traits that are associated with TuYV resistance seem to have particular relevance to a plant’s ability to use Nitrogen more effectively with varieties such as Temptation, Darling and Dazzler doing noticeably better than others in the trials.”
In DSV’s own trials, the new hybrids were found to have around 20% higher Nitrogen efficiency than popular varieties from 15 - 20 years ago, he explains.
“Using the same levels of applied Nitrogen fertiliser, a modern hybrid variety with good overall resilience and a strong disease resistance package like Temptation has been shown to produce around 10% more yield when compared to the older ones.
“These findings have been supported by detailed scientific trials conducted by at the Justus Liebig University in Gießen where it was shown that modern varieties require up to 28% less nitrogen than older varieties to produce one tonne of rapeseed oil.
The DSV trials also showed that when Nitrogen inputs were cut, yields fell but oil contents rose to compensate, he explains.
“Varieties with the highest grain yields from the higher Nitrogen applications are also the ones which have the highest profitability with lower N applications, and much of this is due to higher oil bonuses and lower inputs.
“This why which is why it is very important to select high oil hybrids especially when lower amounts of Nitrogen will be applied.”
Other trials at the Poznan University in Poland have shown around 120 kg N/ha to be the most economical application rate, while higher levels of 180kg and 240 kg N/ha produced only slight yield increases with much higher costs, Simon Kroeger points out.
“This was especially evident in years with prolonged late spring-early summer droughts when the yield potential of oilseed rape cannot really be fully exploited and the second Nitrogen input comes too late to be fully effective.
“Another conclusion from the trials is that on poorer sites with low yield potential lower Nitrogen inputs reduce yields by just as little as 0.1 t/ha whereas on high-yielding sites producing over 5.0 t/ha, yields varied by up to 0.4t/ha depending on the fertiliser regime.
“Overall, the better the site and the better the variety, the more response to your Nitrogen inputs you will get.”
But the timing of the fertiliser application is critical, he stresses.
“With stem growth starting in mid-February, most of the entire fertiliser input should be available to the crop by mid-March at the latest. This means that fertiliser must be applied in good time when spring falls early – oilseed rape needs to build up 80% of its above ground drymatter after winter.”
Despite all the current comments and claims, Nitrogen fertiliser utilisation efficiency is clearly not the main limiting factor in oilseed rape production currently, he concludes.
“The nutrient status of soils, their structure and the availability of rainfall are much more important factors. When conditions are generally good, plants will be able to produce strong roots which are capable of drawing up both nutrients and water to sustain growth.
“But where Nitrogen input levels are limited for whatever reason, it is important to start thinking about incorporating cover crops, undersowing and introducing legumes into the crop rotation as an additional supply of nutrients to the soil and substitute of N fertiliser.”
The UK Experience
DSV UK’s Sarah Hawthorne says the results from Germany support evidence seen in fields across the UK recently with Temptation and now increasingly with Darling and Dazzler.
“Certainly with our own TuYV varieties, we’ve noticed that they are much more tolerant to abiotic stresses such as drought and poor growing conditions, than other varieties.
“There’s growing evidence that the inclusion of TuYV resistance is also connected with high levels of vigour, too.
“Most oilseed rape varieties will stop growing when temperatures fall to 5 – 7oC but TuYV varieties seem to keep growing until much colder conditions prevail. It’s very noticeable when you compare TuYV resistant varieties against others in the field in late Autumn.
“It’s also becoming clear that TuYV varieties handle higher nutrient applications more efficiently with fewer canopy problems resulting.”
Temptation joined the RL in 2019/20 and it currently sits on the 2020/21 RL as suitable for the whole of the UK with a yield of 103% of control and an oil content of 46.0%
The variety’s combination of high yields in challenging conditions and strong all-round disease package will make it one of the most reliable ‘drill and forget’ oilseed rape choices currently available, Sarah Hawthorne says.
“By any standards Temptation is one of the highest performing varieties currently available in the UK.”
Darling and Dazzler joined the RL in 2020/21 as DSV’s first ever triple-layered varieties combining high gross outputs with TuYV, RLM7+ phoma stem canker and pod shatter resistances, she explains.
“Both Darling and Dazzler have been developed in response to the demands faced by growers in particular the need for lower cost management and to address the impact of reduced agrochemical availability in the future.
“They are designed to deliver sustained early vigour in the field to grow through pest and disease attacked whilst exhibiting a range of features that support them from canopy development through to harvest.”