Aiming for rapid growth this autumn

Article taken from the Farmers Guardian

Establish a small-seeded crop at relatively low seed rates in the height of summer is not easy, as the variability seen every year in plant population and eventual yield demonstrates.

With a bit of care, however, crops will grow away strongly, out-growing the attention of seedling pests and diseases and forming a strong stand of plants going into the winter, says Agrovista technical manager Chris Martin.

Encourage rapid growth will be critical this season, following the suspension of neonicotinoid seed dressings on oilseed rape.  Without that protection, crops will be more susceptible to early attack from cabbage stem flea beetle which can wipe out a backward crop as it struggles to come through the ground.

Mr Martin has six key tips to help ensure crops get up and away out of danger, based on several years of Growcrop Gold trials work and a wealth of agronomy experience.

Remove compaction

Oilseed rape is a lazy rooter and is very sensitive to compaction.  It also hates wet soils.  “Use a spade and/or a penetrometer to assess the pan’s position.  Going too deep will press soil up into the compact layer and increase surface slippage, both of which create, rather than cure, problems.”

Help every seed establish

A good seedbed and sowing seed at the right depth is vital for good germination and rapid emergence.  Maintaining moisture is critical, and seedbeds should contain a mix of fine soil and small aggregates to allow good seed to soil contact but minimise capping.

Optimum seed depth is 15mm (0.5in) unless certain herbicide labels dictate otherwise.  This is simple enough with a good drill, but good results can also be achieved when subcasting, he adds.

“Sprinkling seed into the small furrows behind a DD-type roller and covering it with a harrow works well.  Alternatively, coulters can be added to the back of subsoiler legs and manufacturers are developing their own kit.”

Optimise plant population

Several years of Growcrop Gold work has shown plant population is the secret to yield consistency, with 15 plants per linear metre row regardless of row widths providing the best results.

“Most competition occurs between oilseed rape plants within the row,” says Mr Martin.  “Over crowding produces weak, spindly plants which are prone to pest attack.  It also adds to seed costs, which, with hybrid technology allowing breeders to load valuable new traits onto seed, will only go one way.”

In addition, spacing plants out produces on open, branched architecture the following spring which makes best use of sunlight and optimises yields, he says.

Sowing no more than 20 seeds per linear metre is critical to achieve the desired population.  On problem fields, narrower row spacings can be used to raise seed rates, rather than cramming more seed along the row.  “However, do not exceed 60 seeds/sq.m and consider using varieties with good early autumn vigour.”

Seedbed fertiliser

Phosphate is key for early growth.  Accurate placement is important as the nutrient is immobile and small rape plants have poorly developed roots.  “Placing soluble phosphate fertiliser alongside and beneath seeds produces optimum results,” says Mr Martin.  “Incorporating phosphate into the top inch of seedbed also works well.”

Companion plants

Growcrop Gold trials have shown sowing mixes of clover and vetches with OSR improves establishment without creating competition.

“On average they provide a 0.3-0.4tonne/hectare benefit.  As well as benefiting soil structure, companion plants also foil pests like flea beetle and slugs.  No-one really knows why, but this confusion factor has helped growers in France, where companion planting is used widely, to cut out at least one flea beetle spray.”

Seed treatment / early sprays

Mesurol (methiocarb) seed dressing has an effect against flea beetle, says Mr Martin.  “Dressed seed can legally be imported, and we hope for UK approval in time for this autumn.  However, Mesurol is not systemic, so well timed approved pyrethroid sprays will be needed.  Spray at first sign of shot-holing.”