Seed rates succeed in the north
By Wendy Owen
HOW well does HGCA-funded work on reduced cereal seed rates transfer to the north of England and Scotland?
According to a recent open day at ADAS High Mowthorpe in North Yorkshire the principles remain the same.
HGCA-funded work dating back to 1996 shows traditional winter cereal seed rates for early sown crops can be reduced by up to 60% without affecting yield. But much of that research was done at ADAS sites in Nottingham and Herefordshire.
The Yorkshire trial shows growers further north could benefit too, says research consultant David Turley. The most cost effective population for the November-drilled Claire was 154plants/sq m, representing a lower seed rate than normal (table 1).
"We expected that the more northerly sites, including those in Scotland, would need higher seed rates. But in 2001 the pattern of tiller production from Hampshire to Aberdeen was very similar."
Despite an understandable reluctance by the industry to make drastic cuts in seed rates, the High Mowthorpe work confirmed the findings of earlier studies further south, he says.
"Farmers and consultants in the north are taking a cautious approach, although in general they are getting the message that a reduction in seed rates on earlier sowings can be cost effective."
The trials have led to a range of target sowing rates for varying sowing dates, he says, with later sowings requiring a higher optimum target plant population (table 2). Soil conditions at drill-ing influence the final decision.
There is no need to adjust seed rates for different varieties, as those tested responded to lowered plant populations in a similar way.
"In all cases, low plant populations lead to a prolonged period of compensatory tiller production. While this may lead to reduced numbers of ears, often closer to 400 than the 600-700 commonly seen with conventional sowings, the ears are larger due to more efficient light capture."
The timing of nitrogen applications could be crucial in some years, he adds.
"Following autumn 2000, residual nitrogen levels were low in 2001. In that situation we found a benefit from early application of the first nitrogen split of 40kg/ha in late February compared with delaying until April.
"But 2002 is a different year, with high nitrogen residues in the soil. Therefore nitrogen is less critical and I do not expect it to limit tillering this season. Normal application times should be sufficient to maintain yields." *
Seed rate (kg/ha) 19.7 39.3 78.6 157.3 314.6
Seed/sq m 40 80 160 320 640
Actual plant/sq m 28 64 109 216 492
Yield t/ha 8.8 10.7 11.9 12.4 12.6
Optimum plant Typical
(/sq m) rate*
End September 70 45 kg/ha
Mid-October 90 59 kg/ha
Mid-November 140 91 kg/ha
* In good field conditions (1000 grain wt=45.7g)