Many cereal growers are not sowing at high enough speed rates, potentially jeopardising yield potential from the outset, according to Farmacy agronomist Andy Hutchison.
All to often establishment and tillering ability is overestimated, which means plant populations, subsequent ear numbers and grain yield are lower than they should be. The problem is most acute for later drilled crops, but he believes all growers should review seed rates and establishment.
“There’s more leeway for lower seed rates with September sown wheat, as establishment typically averages around 85% and plants have more time to tiller. However, establishment falls to 60-65% by mid-October and maybe just 50% by November/December, with much less tillering capacity.”
Indeed, most wheat only generates 1.8-2 tillers/plant on average, so seed rates must be high enough to reach the target plant population and ear number for maximum yield, he adds.
For September drilling, that target is 150-200 established plants/m₂, while October sown wheat increases to 250-300/m₂. “Work back from there, accounting for germination percentage and a realistic estimate of establishment to calculate the seed rate required.
In-filed variations in soil type, seedbed, topography and weed pressure can result in uneven establishment, which is where variable seed rate plans can really help, he says.
“Ten years of variable seed rate work shows average rate increases are 35-50% where necessary, so we’re not talking small adjustments. But crops and yield will be more consistent, with the greatest benefits on the most variable fields.”
Mr Hutchison acknowledges thicker crops require careful disease and canopy management, but insists this is better than limiting yield from the start.
Barley yields are also strongly determined by ear number, so higher seed rates may be needed. Mr Hutchison recommends at least 300-350 seeds/m₂ for autumn sowing.
“This is usually ok for conventional varieties, but cost and pack size can be prohibitive for hybrids. That makes it even more important to identify where the greatest benefits from increasing rates will be.”