• Why is it important to me as a farmer?
• Why do we need sulphur?
• How to recognise the need for sulphur in the paddock

• Managing the application of sulphur

• Sulphur deficiency is becoming more common due to the increased use of fertilisers that contain only small amounts of sulphur
• Cultivation increases the availability of sulphur to plants, so pasture systems are more likely to show deficiency than cropped soils

• Plants use sulphur in the sulphate form
• Sulphur fertiliser is unlikely to be needed if there is a history of superphosphate use

Sulphur (S) is required for the formation of several amino acids, proteins, and vitamins and for chlorophyll production. It also helps the plant to resist stress from weather, insects and diseases

• In their unimproved state, most soils in south west Victoria did not contain sufficient sulphur to support productive pastures. As levels of pasture productivity increased, sulphur requirements were not detected because the superphosphate originally used to correct phosphorus deficiency also had a high sulphur level (11%) and concurrently overcame any sulphur deficiency
• In the 1980�s, high-analysis fertilisers became available in Australia, making it possible to apply phosphorus with little or no sulphur. At the same time, soil tests for sulphur became available. This made it possible to recognise and assess the need for regular applications of sulphur, independent of phosphorus
• Improved pasture species allow a much higher stock-carrying capacity; but to maintain this productivity, they require a higher level of soil fertility than do native pasture species.
• Fertiliser applications are required to overcome the soil�s inherent nutrient deficiencies and to replace the nutrients that are lost or removed from the soil by pasture growth, fodder cropping or conservation, and animal products, such as milk or meat
• Nutrient redistribution around the farm and the inherent ability of soils to �retain� applied nutrients are other reasons for fertiliser applications

• Sulphur deficiency symptoms include:
  • Plants appear stunted
  • Plants tend to become spindly with thin stems and petioles on clovers
  • Small, pale, yellow-green leaves with lighter coloured veins
  • Poor development and low numbers of nodules on clovers

• Plants severely deficient in sulphur show similar symptoms to nitrogen deficiency
• The major difference between sulphur deficiency and nitrogen deficiency is that sulphur is immobile within the plant, and deficiency symptoms appear first in the younger leaves, whereas nitrogen deficiency affects the older leaves first
• When sulphur levels are low, grasses, because of their larger root system, will compete very strongly for the available sulphur, to the detriment of the legumes. This results in a grass-dominated sward and reduced pasture quality

Figure 1 - Sulphur deficiency in a) wheat and b) sub-clover. � Source: DAFWA

• Soil tests will determine the sulphur status of the farm. In some cases, it may be necessary to analyse plant tissue to determine the sulphur level, especially in cold, wet conditions
• Sulphur is measured using a test called the KCL 40
• Soils in the �adequate� range will generally achieve 95% of potential growth

• Nutrient budgets can also be used to determine the need for sulphur, especially in areas where high analysis fertilisers (urea, mono ammonium phosphate and di-ammonium phosphate) have been used

• The adequate level of extractable sulphur in a soil test is 9-12 mg sulphur/kg
• The nitrogen:sulphur ratio in plant tissue should be in the range 10:1�15:1. Higher nitrogen values could create problems in plant and animal nutrition
• Single superphosphate is the most common fertiliser to supply sulphur to pastures and therefore sulphur fertiliser is unlikely to be needed if there is a history of superphosphate use
• Gypsum supplies sulphur and calcium
• Elemental sulphur is not as soluble as other forms, however all of the sulphur becomes available over time. Cold weather slows the conversion of the sulphur to sulphate by microbes

• Sulphur coated urea will supply both sulphur and nitrogen. This product should not be used at every nitrogen application
• Sulphur in fertiliser is either in the sulphate or elemental form
  • The sulphate form is soluble and can be quickly taken up by the pasture plants but on light sandy soil, it can also be leached. This may result in sulphur deficiency appearing the pasture in spring
  • Elemental sulphur is insoluble and needs to be changed into a soluble form by bacteria so that plants can use it. The finer particles of elemental sulphur in the fertiliser and the warmer the soil, the quicker it becomes available to the pasture

• On soils with a clay loam or clay texture, and low general fertility, sulphur in the sulphate form is preferred. Some sulphur in the elemental form is considered important on lighter soils where leaching occurs
• Because sulphur leaches into deeper layers of the soil more readily than phosphorus, the soil sulphur level in the top 10cm increases at a slower rate with superphosphate application than the soil phosphorus level
• Where pastures are expected to benefit from having sulphur applied, it is generally best to apply it annually. On clay loam or clay soils, apply at least 5kg S/ha year a single superphosphate. Use a higher rate of 5-15 S/ha year on light sandy and free draining soils

• What are the optimum nutrient targets for pastures?
• How do I improve soil without using too much fertiliser?

• What Nutrients do Plants Require? - Department of Environment and Primary Industries, Victoria


• Fertilisers for pastures - (See page 15) � Department of Primary Industries, NSW

• Fertilising Pastures :(Chapter 5)- Greener Pastures for south west Victoria (2006) � Department of Environment and Primary Industries, Victoria


• Sulfur - Soil Health Knowledge Bank � Department of Agriculture, Fisheries and Forestry

• What Nutrients do Plants Require?. Department of Primary Industries, Victoria.
• Fertilisers for pastures. Department of Primary Industries, NSW.
• Fertilising Pastures � (Chapter 5).Greener Pastures for south west Victoria (2006) � Department of Primary Industries, Victoria.

Page Updated: September 2013
Produced by AS Miner Geotechnical