Growers may have to wait until beyond next spring for new official guidelines for fertilising crops in England and Wales.
Outlining the main changes at a Chichester Crop Consultancy meeting last week, Rothamsted Research’s Keith Goulding said he had hoped the successor to the current industry bible, DEFRA’s RB209, would be published this year. But the target had been set back to early 2009 as the proposed publication awaited “peer review”*.
“Now I’m being told that the launch may be at next year’s Cereals event,” said Prof Goulding. That was the AIC’s preferred option, he noted.
However, a draft of the edited manual, minus the delayed grassland section, was sent to DEFRA last weekend, he added. “I’d be very happy to see the arable section released earlier if DEFRA thought it appropriate.”
Revision of RB209, last published by MAFF in 2000, began three years ago and involved 25 contributors.
DEFRA had pledged that it would leave the revision to scientists and that any recommendations would be soundly based on good economic returns, stressed Prof Goulding.
There had been two main drivers – concern over RB209’s nitrogen recommendations and what he described as poor ‘buy in’. “A lot of people didn’t see the old system as useful.”
The advice on phosphorus, organic matter and sulphur had also needed updating.
Outlining the main changes Prof Goulding said the section on soil nitrogen supply (SNS) had been fully revised with the definitions of soil type clarified by a flow chart and identification table.
“Some crops, such as set-aside, have moved down an index which means growers can use more N after them.”
The section covering nutrient management principles and fertiliser use had also been completely revised and gave more information on meeting environmental objectives.
Advice on diagnosing and preventing sulphur deficiency was unchanged but the S deposition map had been updated and the need for S fertilisers emphasised.
“Just about everywhere in the country is now deficient,” he warned.
The new N recommendations for cereals were based on response curves from over 1000 trials results. Advice acknowledged that the yield difference between new and old varieties was about 0.75t/ha, half of which came from the breeding and half from better agronomy.
The extra N needed to achieve that was about 25kg/ha at a break-even ratio of 3:1, the ratio being when 1kg of grain paid for 1kg of N, he explained.
But at current grain and fertiliser prices that ratio was a “quite frightening” 10:1. So a new table to help users make the necessary adjustments should be a welcome step forward from the old publication, Prof Goulding believed.
Despite plenty of debate overall N advice for winter wheat would continue to be based on a farm’s previous grain nitrogen contents, not anticipated yields, he noted.
The economic N optima remained 1.9% for feed varieties and 2.1% for breadmakers.
However, soil nitrogen supply was still the big unknown in making recommendations and more research in that area was needed.
While the new publication was expected to be called The Fertiliser Manual Prof Goulding hoped that the familiar RB209 would still figure in the title.
Expected RBB209 changes
- More types of organic manures covered
- P and K off-take tables updated
- More emphasis on inputs balancing off-takes
- Potatoes: Overall N recommendations decreased but maximums to remain
- Sugar beet: slight changes in potash and sodium recommendations