9 April 1999

Spring barley may be biggest beneficiary from strob sprays

By Andrew Swallow

NEW data from HGCA trials suggests spring barley margins could get the biggest boost of all from strobilurins. But scientists urge caution on drawing hasty conclusions.

"We must stress that these are first year results, and the 98 season was ideal for spring barley," says Arable Research Centres Richard Overthrow, lead scientist on the project. "But these are exciting results and need to be built on."

Optic was grown at Morley Research Centre in Norfolk, and ARC sites at Caythorpe, Andover and Cirencester. The average yield increase from adding a strobilurin to the conventional programme was 0.6-1.0 t/ha (0.2-0.4 t/acre).

However, due to the dilution effect of extra yield on grain nitrogen, more fertiliser could be applied without hitting grain nitrogen content. That took some yield increases to 1.7t/ha.

Even at half-rate, Amistar (azoxystrobin) plus extra fertiliser increased yield by 1.6t/ha. Assuming a price of £85/t for 1.7%N grain that would be worth £136/ha, he notes.

Ensign (kresoxim-methyl + fenpropimorph) results were slightly lower, but still gave a significant increase over the conventional base programme of a quarter rate Opus/Corbel (expoxiconazole/fenpropimorph) tank-mix at GS 30 and GS 49.

Such yield responses are tempting for traditional spring barley growers. But dilution effects could push grain nitrogen contents too low for lager and export malts, which is nearly 90% of the market in England.

"This is one of our biggest fears with the strobs. Growers may find themselves producing barley they cant sell. Even with conventional chemistry there is a strong case for more nitrogen fertiliser," says Bob King of Crisp Malting.

For that reason Mr Overthrow sees the strobilurins having the biggest benefit where growers normally struggle to achieve a malting sample, such as on the clay loam over brash at Cirencester.

There, conventional chemistry plus the full 150kg/ha nitrogen rate gave a sample of 2.3% N. Yet at Andover on chalk land the same combination produced a grain nitrogen of 1.6% N. Including Amistar at Cirencester cut the grain nitrogen to 1.69%.

"A delicate balance is needed to keep samples to 1.7% nitrogen. Growers who are regularly achieving malting samples could end up with too low grain nitrogen levels. Growers may want to think about that and only try strobilurins on a small area," he suggests.

ProCams David Ellerton echoes that view for English growers. "English growers might try a look see approach on a proportion of their area this season. But in Scotland I would stick to routine nitrogens. You are playing with fire suggesting more fertiliser for crops destined for the low nitrogen distilling markets," he warns.

&#8226 Up to +1t/ha over triazoles.

&#8226 Cuts grain N content.

&#8226 Most use on strong land?

&#8226 Scope to increase fert N?


Fungicide Programme N Rate (kg/ha) Yield (t/ha) Grain N %

Conventional only

2x Opus/Corbel 75 5.7 1.64

" " 150 6.4 1.81

Conventional +

2x Full-rate Amistar 75 6.4 1.43

" " 150 7.4 1.64

2x 0.5 rate Amistar 75 6.4 1.44

" " 150 7.3 1.68

Internet tracker

CEREAL disease development and regional risk assessment can be followed with Zenecas Disease Tracker internet service. The main wheat and barley diseases will be monitored by ADAS and SAC consultants and advice on action to take is provided by John Garstang of ADAS Boxworth. The site can be accessed direct at http://www.zeneca-crop.co.uk or through the FWi News and Weather site.

LOCAL Environmental Risk Assessments for Pesticides are a reality – giving sprayer operators a new approach to protecting waterways and staying the right side of the law.

The rules affect 87 category A products, which must always have a 5m buffer near water or 1m near dry ditches.

For a further 362 category B products the same 1m dry ditch buffer applies or a 1-5m buffer alongside water. The latter depends on watercourse width, product dose and equipment used.

"But it will be well into the season and probably autumn before the first drift-reducing star classifications of equipment are ready for use," notes Novartis applications specialist Tom Robinson.

In the field operators will need a map identifying wet and dry watercourses, instructions on the size of buffer zone required and a clear idea of how to achieve the no-spray buffer.

A boom isolation valve or turret nozzle body that can switch off the required number of nozzles will be needed.

But operators should realise that if they get out of the sprayer cab to set the nozzles an additional risk assessment may be required under the Control of Substances Hazardous to Human Health (COSHH) regulations, says Mr Robinson. They will also need to store personal protective equipment safely outside the cab before climbing back on board.

Ensuring product efficacy is not jeopardised by reducing product dose or using drift reducing equipment to narrow buffer zones is also important, he notes. "Potato blight and blackgrass are two good examples."

For each LERAP operators will need to record the date, the assessor, % dose, watercourse size, sprayer star rating and final buffer size chosen, he adds. "If that is too much stick with 5m and record the decision."

All arable farmers have been mailed an up to date list of products requiring buffer zones.

&#8226 87 cat A products – 5m buffer.

&#8226 362 cat B products – LERAP.

&#8226 Equipment ratings in autumn?

&#8226 Product list sent to all farms.