Modern oilseed rape varieties are nearly 30% more Nitrogen efficient than the highest yielders from just a few years ago, says DSV’s Simon Kroeger.
With Nitrogen utilisation increasingly in the spotlight, trials are showing a number of factors contribute to a plant’s ability to make better use of nutrients and cannot be tied to a specific gene, he says.
“The highest yielding oilseed varieties are also the ones that have the best Nitrogen Utilisation Efficiency (NUE).
“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.”
“In particular, traits 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 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 points out.
“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 in Germany 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 which is why it is always important to select high oil hybrids especially when lower amounts of Nitrogen will be applied.
“Other trials in Poland have shown around 120kg N/ha to be the most economical application rate, while higher levels of 180kg and 240kg N/ha produced only slight yield increases with much higher costs.
“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.”
Despite all the current comments and claims, Nitrogen fertiliser utilisation efficiency is clearly not the main limiting factor in oilseed rape production currently, Simon Kroeger 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.”