Three Ways to Identify Sulfur Deficiency in Corn

As an essential nutrient for crop health and growth, sulfur is required for protein to synthesize and assists the plant in completing many of its main functions. Long periods of sulfur deficiency can severely impact yield, so early identification and treatment is crucial for farmers wanting to protect their bottom line. Use one or all of the following three methods to examine your corn for signs of sulfur deficiency—if identified early enough, you could save your crop from significant stress.

1. Look at the new/younger leaves

Sulfur does not remobilize to younger parts of the plant from older parts as readily as nitrogen. Thus, inspecting new or younger leaves for signs of deficiency is necessary. Yellowing of new leaves will be apparent with a sulfur deficiency, often with interveinal striping. Older leaves will remain green, so keeping a close eye on emerging leaves is the best way to determine if the crop is deficient in sulfur.

From first look, yellowing of the plants may be mistaken for other deficiencies, such as nitrogen. A misdiagnosis of nitrogen deficiency treated with nitrogen fertilizer could cause a sulfur deficiency to worsen. The best way to decipher between a nitrogen or sulfur deficiency is to look at the difference in old and new leaves; nitrogen deficiency will typically appear as yellowing of older leaves, while sulfur in young leaves.

2. Scout lower spots in the field

There may not be visible signs of deficiency consistently across the field, so it’s important to focus on areas where symptoms are more obvious. Sulfur deficiency can be common in lower laying areas of a field. Other factors that can lead to sulfur deficiency symptoms are corn planted into heavy residue and shallow seeded corn. Some areas may appear to have mild symptoms, while others severe—ensure you are scouting in various areas to best understand the conditions of your crop.

3. Take a tissue sample

As discussed in our previous article on sulfur deficiencies, soil sampling coupled with tissue sampling can be a great diagnostic tool for determining sulfur deficiency. Taking both a soil and tissue sample from the “affected” area and comparing to ones taken from the “healthy” area will help to determine sulfur deficiency in the crop. Be sure to collect a sufficient amount of plant tissue to test; in plants less than four collars, sample the whole plant, collecting about 15 to 20 plants to test. In older plants, sample the most recently matured leaf, collecting about 10 to 15 plants for sampling. The sulfur concentration combined with the nitrogen to sulfur ratio will help determine deficiency in the plant—a high nitrogen to sulfur ratio and low concentration of sulfur in the plant means the crop is likely sulfur deficient.

Comparison of Small Corn Plant with and without Sulfur Application. Photo © Brian Lang, Iowa State University Extension and Outreach Soil Fertility online site.

How Smart Nutrition™ MAP+MST® can help

For corn plants, half of the sulfur the plant will take up to maximize production occurs after the plant reaches the reproductive stages, or halfway through the corn plants’ life. It’s important to ensure enough sulfur is available to corn plants to be taken up during this time, which means selecting a sulfur fertilizer source that won’t leach out of the root zone.

Smart Nutrition MAP+MST contains elemental sulfur, so the sulfur has to be oxidized before it is plant available. This allows for a delayed or slow release, so the sulfur is available later in the season and helps to protect against leaching. Smart Nutrition MAP+MST can help you meet your sulfur application needs. Ask your agronomist or local Smart Nutrition rep about adding it to your fertilizer program.