BEWARE of the trend towards low seed rates. Even at earlier drilling dates, it could be a false economy, according to results from the Crop Care trial site at Saxham, Suffolk.
Wheat sown on 24 September last year at a low seed rate yielded 0.66t/ha (5cwt/acre) below that drilled at conventional seed rates.
So spending more on extra seed is worthwhile, says Colin Myram of the Crop Care Group. At wheat prices of £75/t and seed at £275/t, the average return from extra seed works out at £19.75/ha (£8/acre).
In the trials on the clay loam site near Bury St Edmunds a range of wheat varieties were compared.
The low seed rate plots were drilled at about 110kg/ha (44.5kg/acre), with the exact rate calculated in accordance with the thousand-grain weight for each variety. The target plant population was 190 plants/sq m.
The high seed rate was double this. The average seed rate worked out at 220kg/ha (89kg/acre), and the target plant population was 380 plants/sq m.
At later drilling dates, the yield benefits from increasing seed rate continue (see table), but overall yield declines sharply.
"Early drilling is critical," says Mr Myram. "If seed had been available earlier, we would have drilled closer to the beginning of September."
The higher seed rates do not depress grain quality – quite the reverse. Mr Myrams results show specific weights are lower across all drilling dates with low seed rates.
At the September drillings, the varieties which showed most return from a higher seed rate were Rialto, Savannah, Harrier and Consort.
With winter barley, the message is similar. The payback from higher seed rates is, on average, £22.30/ha (£9/acre). "We picked up a similar trend last year," says Mr Myram. "Results show growers should drill early, without a drop in seed rates."
The barley trials compared a high seed rate – aiming for 280 plants/sq m – with one half this rate.
Varietal differences were more pronounced. Fanfare, Halcyon and Baton benefited most from a higher seed rate at September drillings.