Plea for grass blends
MIXTURES account for nearly all the grass varieties sown on UK farms. So it makes sense to enter them alongside the single varieties in recommended list trials.
That is the logic behind a range of herbage mixtures developed by Tim Ball of CPB Twyford, one of the few remaining UK commercial grass seed breeders.
"97% of grass is sown as mixtures," says Mr Ball. The main reason cited was that blends were more adaptable than "straights" to changes in sward management.
Mixtures reduce risk, he explains, by evening out seasonal production, and avoiding the post-flowering drop in quality and loss of ground cover which occurs in single varieties.
Using several varieties cuts the risk of disease and lessens the impact of winter damage, he adds.
However mixtures were not automatically better. Getting good results involves choosing the best matching performers based on a wide range of trials and local knowledge, he explains. The firm uses new varieties both from foreign companies and its own breeding programme. But only when they have proved themselves able to improve the overall mix.
Depending on the make-up there were also potential yield benefits "over the best single varieties".
To prove its point the firm, which offers eight mixtures claimed to meet 95% of all needs, has entered some into official trials. One is Meat Milk – a blend of intermediate and late perennial ryegrasses, timothy and white clover.
Simulated grazing trials by NIAB at Seale-Hayne, Devon, in 1993, on swards sown in 1991, showed the mix gave 20% more dry matter in eight cuts than the intermediate perennial ryegrass controls.
The best single variety produced only 10% above the controls, notes Mr Ball.