The high use of superphosphate, containing 10.5 per cent sulphur, has prevented sulphur deficiency in many situations. However, in recent years the trend has been to use less fertilisers containing sulphur. Sulphur deficiency in the pasture phase on sandy-surfaced soils will become more prevalent as the interval between maintenance sulphur applications increases. Deficiency symptoms The symptoms of sulphur deficiency in subterranean clover and burr medic plants are similar to those of nitrogen deficiency. Since chlorophyll production involves sulphur, deficient plants are usually a pale green to green-yellow in colour.
Cotyledons also become yellow, with some reddening of the petioles of young leaves.
Often the cause of nitrogen deficiency is a lack of capacity to fix nitrogen in their nodules or the absence of rhizobia. Their nodules are either small and white inside, or a yellowish to green brown colour if they have become ineffective. The nodules on sulphur-deficient plants are generally functional, that is, they are a bright pink to red colour inside. However, the capacity and life of the nodules tends to be reduced. Sulphur deficiency in the paddock is often patchy, with clumps of deficient and healthy plants close together.