19 April 1996

…and Wiltshire unit fortifies its top-dressings

Sussing the need for sulphur is not easy. But experiences in Hants, Wilts and the north provide useful pointers for all growers facing this increasingly common problem. Andrew Blake, Amanda Dunn and Robert Harris report

SOIL, tissue and grain analyses carried out by ADAS since the early 1990s on a Wiltshire farm have convinced the grower he should apply sulphur to his crops.

The 364ha (900-acre) all-arable Manor Farm, Stapleford, near Salisbury, which Geoffrey Moore runs with brother, Roger, relies heavily on seed production.

Concern that yield and especially quality could be compromised by hidden S shortage led him to switch to a sulphur-containing fertiliser for first top dressings in the 1993/94 season. "The penalties for high screening levels in seed crops can be severe," comments Mr Moore.

The chalkland farm produces winter wheat, winter and spring barley, grass seed, linseed and, in most years, peas. But without oilseed rape, an early indicator of sulphur deficiency on other farms, the brothers were prompted to introduce S both by ADAS and results from trials by the local Chalkland Cereal Group and commercial organisations in the area.

"ADASs leaf and grain analyses showed our N:S ratio was already marginal by then," explains Mr Moore. "This year the Cereal Group will be doing replicated trials here to examine the effects on yield and quality more closely."

Sulphur inputs so far have been confined to the winter cereals. But he suspects spring barley and grass will soon need treatment. Plenty of early moisture in 1995, giving an average spring barley output of 7t/ha (2.8t/acre), could have masked shortages, he suspects. "In dry springs weve only been getting about 2t/acre."

Application options

Various options for applying the extra sulphur were considered, but the choice of ICIs Sulphur Gold was soon made, he says. "I am keen on it because the settings for our Amazone spreader are identical to those for Nitram. We tend to use SP5 products because were on 20m tramlines and we dont get many spreading days that arent windy."

Cheaper imported materials have been tried in the past with variable results. "But their flow rates can vary which means you cant guarantee the accuracy of spreading." Some blends contain a lot of dust which can lead to striping and flat crops, he adds. "One spoiled field destined for seed or malting could soon soak up the £8/t or so we might have saved."

Applying the S as pellets in the autumn would have meant extra expense. With few slugs the farm has no need for a quad machine and applicator. "It would also involve a separate operation."

Currently he applies the first of three cereal top dressings as Sulphur Gold. "We use 1.5 bags an acre as recommended. This provides 45 units of N and 17 of S." Maximum N rate on the wheats, which last year averaged 10.6t/ha (4.2t/acre), is 225kg/ha (180 units/acre).

On the economic side Mr Moore estimates that adding the sulphur costs about £3.30/ha (£1.35/acre). He admits he has been unable to assess the benefits directly, for example through split field tests. "We have done all the winter cereals as advised."

Sulphur convert Geoffrey Moore relied on local trials results and grain and tissue testing to formulate his fertilising policy.