Your corn crop is out of the ground and growing, but it looks stressed. Many of the plants are a pale green, some are stunted. You wonder if what you’re seeing is a nitrogen deficiency. Or maybe, you think, it’s a sulfur deficiency.
The two problems look similar at first glance, but there are key differences you can observe, says Ken Ferrie, Farm Journal Field Agronomist.
“Nitrogen deficiency shows up in the older leaves at the bottom of the plant. Sulfur deficiency shows up in new growth—at the top of the plant or in the whorl of corn plants. That’s because plants can move nitrogen from the old growth to the new growth, but sulfur, unlike nitrogen, is not mobile,” Ferrie explains.
Tissue and soil tests. If you suspect a sulfur deficiency, confirm your observations with tissue analysis and soil tests. Have plant tissue analyzed several times during the season—early, mid-season and late. To fertilize effectively, you need to know when plants are running short of sulfur, and then time applications accordingly.
Sulfur is incredibly important to corn production – a bushel of corn removes 0.08 lb. of sulfur in the grain and 0.09 lb. in the stalk – 0.17 lb. total.
“A 200-bu. corn crop takes up 34 lb. of sulfur per acre,” Ferrie says. “That figure is even more impressive if you think of it in terms of sulfate, which is the form of sulfur that plants actually can use—102 lb. of sulfate per acre.”
In crop production, sulfur’s most critical job is helping produce protein molecules and amino acids, which are required to produce chlorophyll, lignin and pectin. To do that, it assists in photosynthesis, the process in which plants convert sunlight into chemical energy.
An Important Supporting Role. Another key benefit to not overlook is that sulfur helps metabolize nitrogen. “If a tissue test reveals a sulfur deficiency, it probably will show a nitrogen deficiency, as well,” Ferrie says. “Both are structure-building components, so sulfur (like nitrogen) is required early in the season. The plant needs sulfur to build the factory that will produce the fruit.”
Insufficient sulfur results in stunted growth and can delay crop maturity.
“Sulfur-deficient 112-day corn will act like a 115-day corn; it tassels and finishes later,” Ferrie says. “In other words, plants become inefficient, producing less growth per heat unit per day.”
As you evaluate the amount of sulfur your corn crop might still need this season to perform its best, consider the following articles featuring Ferrie’s agronomic insights and expertise on the topic.
Want 200-Bu. Corn? You’ll Need 34 Pounds Of Sulfur Per Acre
Your Fields Are Likely Low On Sulfur: Here’s How to Fix It
The Systems Approach to Sulfur
Ferrie: That Yellowing and Striping You’re Seeing are likely Zinc and Sulfur Deficiencies
Ferrie: Treat Sulfur Like A Macronutrient In Corn to Boost Yields
