The Secondary Nutrients & Plant Growth - Sulphur's Role

Sulphur is an essential component in the synthesis of amino acids required to manufacture proteins. Sulphur is also required for production of chlorophyll and utilization of phosphorus and other essential nutrients. Sulphur ranks equal to nitrogen for optimizing crop yield and quality. It increases the size and weight of grain crops and enhances the efficiency of nitrogen for protein manufacture. Crops that have a high nitrogen requirement must have adequate sulphur to optimize nitrogen utilization. Sulphur increases yield and protein quality of forage and grain crops along with production and quality of fiber crops.

Sulphur deficiency is characterized by stunted growth, delayed maturity and general yellowing of plants. Yellowed plants are also characteristic of nitrogen deficiency. However, unlike nitrogen deficiency which begins in the older leaves and progresses upwards the plant, sulphur deficiency symptoms begin in the young, upper leaves first. Sulphur deficiencies are often misdiagnosed as nitrogen problems, leaving growers to wonder why their nitrogen applications are ineffective.

In many crops, an acute Sulphur deficiency causes the entire plant to turn yellow. In crops like corn and small grains, however, yellow stripes that run parallel to the leaf blade are common. Sulphur deficiency is most frequently observed on very sandy soils with a low organic matter content during seasons of excessive rainfall.

Fertilizers that provide Sulphur include potassium sulfate (18% S), potassium-magnesium sulfate (23% S), magnesium sulfate (14% S), gypsum (16.8% S), ammonium sulfate (23.7% S) and elemental Sulphur (90% S). Under most soil and climatic conditions, 5 to 10 Kg of Sulphur per acre should be adequate. For crops that have a high nitrogen requirement (corn, small grains, tobacco and cotton) and are grown on sandy soils, Sulphur can be applied at planting or along with post-plant nitrogen applications.