A balancing act

1 April 2000

A balancing act

Our Hampshire contender is off to a flying start in the malting barley challenge. Hes upping nitrogen and using new technology to fine-tune crop nutrition. Gilly Johnson visits.

GROWING crops in a thin layer of grade 3 soil over chalk is like hydroponics: nutrition really matters. What you get out ultimately depends on what you put in – and thats why plant nourishment is the number one priority for Hampshire producer John Waterston.

Theres not enough soil to provide for all the necessary nutrients, so the crop needs spoon feeding with certain trace elements as well as nitrogen, potash and phosphate. But with malting barley, Mr Waterston must also take quality targets into account. It makes for a tricky balancing act on this typical downland site.

Nitrogen – but not too much – is critical for quality. With lengthy experience of spring barley, Mr Waterston knows how to meet a malting spec more often than not.

But strobilurins have moved the goalposts. These fungicides have the potential to boost yield and dilute grain nitrogen – which should allow the use of more nitrogen without jeopardising quality. At least, thats the theory. Boldly – or is it rashly? – Mr Waterston is increasing nitrogen on the challenge field of spring barley this season.

Agronomist Mark Glyde of Crop Management Services recommends upping the fertiliser by 19kgN/ha (15 units/acre) to 144kgN/ha (115 units/acre). Adding to the arguments in favour of more N, residual N levels are down at about 30kg/ha, due to extremely wet weather in February.

The application will go on in two equal splits – the first "as soon as we can just see the tramlines at one true leaf, GS11, the second when the crop meets between the rows, GS22-23."

The split ammonium nitrate treatment costs more in application but is a worthwhile insurance against extremes of weather, says Mr Waterston.

Bumper yield

The quality target chosen is 1.65% grain nitrogen, which should trigger a £17/t premium, according to the malting contract. Last years crop averaged 1.62%, with a bumper yield of 6.8t/ha (55cwt/acre). Can the challenge field repeat this performance?

Although N was lower last year, at the conventional dose rate, the yield was strob-powered; it was fuelled by two doses of a quarter-rate Amistar and Opus (azoxystrobin and epoxiconazole) mix. Incidentally, strobs seem to help prevent brackling, which has been a problem in the past, notes Mr Waterston.

This year the plan is to switch to new strob Twist (trifloxystrobin) with a triazole partner – but only if it is priced competitively. Rhynchosporium is the main threat for Optic, which has a resistance rating of just 4, and Twist promises a powerful new solution.

Back to nutrition. The farm has been soil sampled using GPS and the Soyl system; theres a lot of variation, so Mr Waterston is able to make considerable savings through variable application of potash and phosphate. He reckons the investment in sampling and mapping – £16.19/ha (£6.55/acre) – will be repaid. "We should save £6,000 a year." With such inherently high pH, K is locked up in the chalky soil and so the crop needs potash in spring.

Magnesium and sulphur are deficient. Kieserite – magnesium sulphate – does the two jobs in one, and is applied in March. Mr Glyde also uses copper/magnesium and a copper/manganese (as inorganic, acidified Phosyn products) treatments.

The growth regulator programme (a single dose of eighth to a quarter dose of Terpal) will depend on plant density and weather – "we dont go near the crop if its hot and dry, and is under drought stress." The main aim is to prevent brackling head loss and to shorten stems slightly.

The challenge field was drilled in the first week of March – a tad later than Mr Waterston was hoping, but February was too wet. But in the event, conditions at drilling were perfect – so the crop "has got off to a flying start." Even the February floods could be a blessing in disguise; the chalk subsoil soaks up water and will provide a useful moisture reservoir if a drought develops later in the season. So far, so good for Mr Waterston. Fingers crossed as the challenge unfolds….

&#42 Location: Chilton Manor Farm, Chilton Candover, Alresford, Hants. 607ha; arable and sheep

&#42 Rotation: Varied. On the lighter soils, break, wheat, spring barley, then winter barley or stubble turnips, then back to spring barley

&#42 Challenge field soil type: Easily worked but lower yield potential grade 3 downland over chalk; 20cm soil layer in thinnest parts

&#42 Variety & seed rate: Optic @ 400 seeds/sq metre, dressed with Raxil S

&#42 Drilling date: 5 March

&#42 Cultivations: Over-wintered stubble, then ploughed and pressed

&#42 Previous crop: Second wheat

&#42 Expected yield: 6.2-6.8t/ha

&#42 Quality target: Max 1.65% grain nitrogen

&#42 Nitrogen: 144kgN/ha

&#42 Potash/phosphate: P is usually satisfactory; K applied in spring using variable application

&#42 Trace elements: Magnesium and sulphur as kieserite; manganese and magnesium with copper as inorganic feeds

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