To reduce the amount of Nitrogen and Phosphorus applied to varieties that have high nitrogen use efficiency without suffering a yield or sugar reduction
Certain varieties are better adapted to different environmental conditions e.g. soil types. Some varieties also have higher nitrogen use efficiency, which means that it will grow just as well with reduced fertiliser rates as it would with a higher rate. This is due to the fact the fertiliser is used more efficiently with a lower amount lost to external sources.
Better matching Nitrogen application to variety requirement could lead to less lodging, higher chance of maturity at harvest and in turn higher sugar yields.