Plant Tissue Tests – High Nitrates – Low Sulphur

Sulphur Deficiency

It has become apparent this season that with warm autumn temperatures and ample moisture around in the Southern Region that soil activity has been high. High rates of mineralisation in the soil has seen many early plant tissue tests showing high levels of nitrate and also seeing low sulphur levels.

Nitrate and Sulphate are both negatively charged nutrients and can compete for plant uptake. As a result when high soil nitrate is present sulphate uptake can be reduced.
In the Southern cropping regions high rainfall events are moving across the landscape. With many plants already showing signs of sulphur deficiency, after high rainfall events in many areas, further sulphur limitations may be seen due to sulphate being prone to leaching in many soil types.

Sulphur, like nitrogen is required for amino acid and protein formation and also oil formation especially in crops such as canola. Therefore it important to ensure adequate sulphur is supplied to the plants along with nitrogen.

Plant tissue testing is a useful and essential management tool for monitoring current crop nutrient status. For sulphur management, a ratio of greater than 19:1 of nitrogen to sulphur often indicates a sulphur deficiency.


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