4 December 1998

Trials indicate the importance of seed price

RESULTS from national list trials of genetically modified herbicide tolerant oilseed rape and sugar beet varieties show just how important seed price will be.

Yields are yet to match conventional or hybrid varieties, explained Simon Kerr, NIABs head of potatoes and sugar beet. In trials using conventional weed control techniques GM winter rape lines were up to 7% behind the best hybrids, while GM beet yielded 8% less.

The gap closes slightly in sugar beet when a total herbicide is used on the GM varieties, mainly because there is less of a growth check than with conventional herbicides, noted Mr Kerr. In 1997 and 98 that was typically worth 2% more yield.

But the remaining shortfall means seed price will play a big role in deciding the future of GMHT varieties on UK farms, he explained. Examples, using a theoretical 10% price premium for seed, proved the point.

On sites with low weed pressure GMHT beet would be £57/ha less profitable than conventional varieties, despite a £70/ha spray saving.

The picture becomes more favourable where high weed pressure requires an outlay of £250/ha on conventional herbicides. Not only are herbicide costs higher, but yields are equivalent due to a 4t/ha growth check caused by the hefty conventional programme. The result is a £209/ha better margin for the GMHT crop.

Similar calculations for winter rape show GMHT varieties £34/ha behind in a low weed scenario, but £20/ha ahead under higher weed pressure. &#42

Sugar beet benefits

GMHT Conventional

Weed pressure all low high

Seed 127 116 116

Herbicide 30 100 250

Yield 58 62 58

Output 1682 1798 1682

Margin 1525 1582 1316

Diff +57 -209