No penalty for seed rate cuts
WHEAT growers facing hefty growth regulator costs to keep over-thick crops standing this season might have moderated the expense by cutting their seed rates hard.
SAC trials suggest there is no resulting yield penalty, provided seed-bed quality is good and the risk of plant loss through slug and bird damage is relatively low.
Indeed, a slight yield improvement was found in the SACs 1997 wheat systems trial. Early-October drilled plots of Riband, Madrigal and Crofter had seed rate cut by 33% on the high yielding East Lothian site.
The trials top seed rate was 450 seeds/sq m, representing 248kg/ha (about 2cwt/acre) for seed with a thousand grain weight of 55g. The 33% lower seed rate was 300 seeds/sq m.
"The main message from this and a similar 1996 trial is that growers can cut their seed rates substantially, without yield penalty, provided seed-beds are good and theres little risk of significant plant loss," says SAC research agronomist David Cranstoun.
The lower seed rate also reduced lodging for the relatively weak strawed Crofter, particularly where the standard 200kg N/ha (178 units N/acre) was cut by 50kg N/ha (45 units N/acre). All varieties received a full dose of 5C Cycocel at GS31.
"Seed rates are still based on tradition generally and if anything theyre rather higher than 450 seeds/sq m. So it would pay growers to look at what theyre using more closely," suggested Mr Cranstoun.
"Unlike further south, we dont need to worry about germination being delayed by drought – its rare for us to have a dry September.
"I wouldnt be comfortable with a spring plant population below 200 plants/sq m, so I wouldnt recommend a rate below 275 seeds/sq m for wheat drilled earlier than October," he advises.
Assuming a seed price of £300/t, a one-third seed rate reduction from 248kg/ha to 165kg/ha (2cwt to 1.3cwt/acre) would bring a saving of £25/ha (£10/acre). *