Tissue test to judge true sulphur requirements
By Robert Harris
TISSUE testing for sulphur shortage is a vital tool to assess crop shortage and all arable growers should use it, says fertiliser manufacturer Kemira.
That matches ADAS advice (Arable, Jan 24). But Kemira disagrees that growers are being subjected to commercial pressure and maintains plenty of crops will need S this spring.
Unfortunately, tissue testing needs to be done during peak growth, when crops are growing most actively – usually April for oilseed rape and May for cereals. That means results will be too late to protect this years crop, as S is best applied with the first top dressing, says Paul Sweeney, Kemiras research and development manager.
"Intensive arable growers on light land should apply it routinely, on oilseed rape, milling wheats and perhaps other wheats as well."
Paybacks are big, he maintains. The recommended application rate is 112kg/ha (90 units/acre) of SO3 for oilseed rape, and 56kg/ha (45 units/acre) for cereals. That costs £10 and £5/ha respectively, but with typical yield responses of 20% and 10%, payback ratios are 10:1 for rape and 15:1 for cereals.
Mr Sweeney agrees heavy and medium land growers are unlikely to benefit yet. But annual tissue testing will establish how quickly levels are falling. At £15/sample, it is a cheap forecast, he says.
• Commercially, Kemira stands to gain nothing, Mr Sweeney claims. "We want farmers to buy our products, but we dont really mind if they use sulphur or not. Sulphur products cost a little more, but that is taken up in production costs. Our margin is no different."n