How To Identify Sulfur Deficiencies
Sulfur deficiency has increasingly become a problem in many field crops in recent years. While these nutrient challenges are growing, the problem can be easily corrected with proper diagnosis and nutrient application.
The biggest challenge for many growers with sulfur deficiencies is diagnosing the problem. The tell-tale symptoms of yellowing leaves are often confused with nitrogen deficiencies. The key to identifying sulfur deficiencies is to make sure it is not ruled out when growers are troubleshooting crop growth problems.
Nitrogen and sulfur follow a common physiological process in plant uptake, resulting in similar symptoms in the early growth stages of plants. Warning signs can include overall leaf and plant yellowing, spindly plants and interveinal striping. These similar symptoms often occur when plants are small and there is a severe nutrient deficiency (low soil supply and no fertilization).
While plant response from nitrogen and sulfur fertilizer applications can be similar, sulfur is not translocated as readily in plants as nitrogen. This means that, depending on the nutrient deficiency, the symptoms will appear in different parts of the plants. Sulfur deficiencies will appear as yellowing of new leaves (in the whorl with interveinal striping). If a plant is showing signs of nitrogen deficiencies, the lower (older) leaves will appear yellow, from the leaf tip to the base down the midrib of the plant.
One way to identify sulfur deficiency is through tissue diagnostic sampling. Start by collecting samples from areas suspected of deficiency and from healthy areas of the field for comparison. The difference in sulfur tissue concentration should have some indication if sulfur deficiency is present. Some crops respond to in-season sulfur applications if deficiencies are determined early.
Unfortunately, soil sampling isn’t necessarily an effective method of determining fertilizer application recommendations. However, when coupled with tissue samples, soil samples can aid in determining if sulfur deficiency is present. Take soil samples in the same areas described above, a composite from the suspected area and a composite from the healthy area for comparison. Sulfate-sulfur is mobile within the soil profile so depending on soil characteristics, levels are variable.
If a sulfur deficiency is misdiagnosed as a nitrogen deficiency, the application of nitrogen fertilizer can worsen the sulfur deficiency.
Unsure about nutrient deficiencies or fertilizer needs for your crop? Talk to your agronomist or a local Smart Nutrition rep. Adding Smart Nutrition™ MAP+MST® to your fertilizer program can help you meet your sulfur application needs.