1 September 1995

S factor adds to lime needs

DONT overlook the acidifying effects of sulphur-containing fertilisers when gauging the liming needs of arable land this autumn, warns the Agricultural Lime Producers Council.

Crop removal of calcium and leaching can account for around 400kg/ha/year (3.25cwt/acre/year) of lime. Nitrification of nitrogen fertiliser also "uses" lime – about 330kg/ha (2.7cwt/acre) for a 186kg/ha (150 units/acre) N application of ammonium nitrate.

More balancing needed

However, the additional acidifying effect of ammonium sulphate can mean three times more "balancing" lime is needed.

A typical crop receiving 200kg/ha (160 units/acre) of nitrogen as ammonium sulphate will use up about 1.5t of lime a hectare annually (12cwt/acre/yr).

It is also important to apply only the required amount of sulphur to compensate for the reduction in atmospheric depositions to avoid increasing acidification.