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Clean break crop success

Agronomy Issues
09.01.2020
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The last time the UK experienced such a difficult autumn establishment season, in 2012-13, the subsequent area of spring oilseed rape increased by over 750% - from less than 10,000 hectares to over 91,000 ha.

In the search for viable spring crop options this season, growers report spring oilseed rape can work. But the crop demands very close attention to agronomy, and controlling growing costs, to make realistic returns.  

Spring break with OSR

Investment to achieve good returns from spring oilseed rape is more about spending time, rather than money, advocates Oxfordshire growers, Nigel and Margaret Lawrence. From the moment of emergence, the crop is under intense pressure, with timely intervention crucial to prevent losses.

Their 70 hectares of spring OSR a year, at Shirburn Farm, near Watlington, is an integral part of a whole farm rotation approach to profitability, across the 300 hectares of arable cropping. The benefits of spring OSR to the following autumn-sown wheat crop, in terms of control of grass weeds and as a timely and easy seedbed entry, for example, are often worth as much as the crop itself.

Oxfordshire grower Nigel Lawrence encourages more growers to give spring oilseed rape a chance as a useful break crop in a profitable whole farm rotation.

Achieving consistency with yields have been the Achilles heel of the crop, he warned. Combine monitoring has shown yields fluctuating from over 3.2 t/ha, down to 0.5 t/ha across the farm. The Lawrences set an overall average of 1.8 t/ha as a realistic performance budget, which has typically been achieved and, providing costs can be minimised, is viable in the context of the whole farm rotation. 

 

As soon as the spring OSR is planted, daily inspections are started for any sign of flea beetle activity. From the first cotyledon emergence, flea beetle can decimate seedling growth overnight, warned Mr Lawrence.

“It’s hand and knees inspection for the first signs of beetle migration, and then being prepared to act quickly.”

Control strategy has centred on Hallmark Zeon to target flea beetle activity, and for repellence effect to limit the speed of further beetle migration. However, control has been getting noticeably more difficult over recent years, he highlighted. The focus is on getting crops established as quickly as possible, but also at a low cost to minimise financial risk in case of failure. 

He has mostly relied on home saved seed of conventional varieties; Tamarind has proven the most reliable variety on the farm, with new seed stock grown every couple of years. Even with paying the full royalty cost on all the seed sown, it is still a relatively low initial investment.

Such is the pressure from insect damage, the Lawrences typically sow seed rates of 6.5 – 7.5 kg/ha, aiming to establish 150 plants per m2, with seed rates tailored to seedbed and growing conditions. With the low cost of seed, last year they trialled increasing seed rates, to as much as 10 kg/ha, however results were not significantly different in established plant population and no advantage in yield. 

Nigel Lawrencde

All the farm’s crops are established with the minimal number of cultivation passes. After harvest wheat stubbles are surface tickled to encourage grass weed chit, and then sprayed off. Further germinated weeds are killed before the spring crop establishment, moving as little soil as possible to reduce costs and retain structure. 

Mr Lawrence advocates minimal cultivation passes keep black-grass at the surface, where it can be effectively targeted.

He points out that spring OSR germination and initial growth can be slow, depending on soil conditions and temperatures, which makes even and precise seed placement so important. No fertiliser is applied in the seedbed, but is followed up with a total of 125 kg N/ha, typically split in two or three applications in quick succession as the crop rapidly develops through growth stages.

As soon as seedlings are seen emerging, fields receive metazachlor as a pre/peri emergence herbicide, with the option to top up with clopyralid + picloram for cleavers and mayweeds where required. All the established fields have a graminicide to reinforce black-grass control, but he’s mindful the efficacy appears to have been waning in recent seasons, pointed out Mr Lawrence.

Whilst common belief with winter oilseed rape is that pollen beetle move onto open flowers as soon as possible and stop further damage, Mr Lawrence’s experience is that in spring rape they will continue to feed voraciously on green buds lower down the stems, even when top flowers are fully open.

Hallmark Zeon has been his first option in previous seasons, but issues with resistance and now the loss of pymetrozine is of further concern for the crop. “Spring OSR doesn’t have sufficient flower heads to tolerate loses to pollen beetle damage, and there’s too little time for compensatory growth that can help out in winter crops,” he advised. New anti-resistance options, including indoxacarb/acetamiprid, may need to be looked at in future.

The simple low-cost fungicide strategy orientates around Amistar as a standard application - to limit Sclerotinia effects and maintain green leaf area for the short growing season crop – followed by tebuconazole. In a high disease risk season, a second tebuconazole may also be required.

The immense importance of break crops are not lost on Nigel Lawrence. After 15 years of simple - and profitable - continuous wheat, the legacy of black-grass left the farm almost uncroppable, with several years of rotational fallow. Now, with the rotational approach of mixed crops and minimal pass cultivation strategy, he believes it’s back on an even keel for sustainable productivity and profitability.

Other spring break options for growers this season

Soya

Increasing interest from growers, with more reliable varieties for UK conditions. Limited agronomic experience. Few contracts available for this spring.

Beans

Winter sown crop typically more reliable than spring sown. Early summer rainfall crucial for yields. Performs better on moisture retentive soils. Sow early varieties in northern regions. 

Peas

Huge interest for 2020 sowing. Legume crop benefit for following crop. Can perform well on lighter soils. Early maturing varieties potentially more suitable for northern regions and Scotland. Register for this season’s Syngenta PGRO Roadshows for the latest agronomic insight and advice. 

Lupins

Market for high-protein seed for animal and aquaculture feed. Some varieties may be later maturing. Only sow once soils are warm and dry, from mid-March. PGRO advice available.

Maize

Market for industrial crop or livestock feed. Not a true cereal break. Good options for grass weed control. Late harvest may restrict autumn crop establishment. Join the Maize Growers Association for agronomic advice.

Find out more OSR agronomic topics and growers' experiences on the dedicated iOSR pages 

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