Corn Corner: Less sulfur in the air renews discussion about sulfur as fertilizer.
Tom J Bechman | Jan 04, 2018
People at meetings are talking about sulfur for corn now that there is less sulfur in the air. My fertilizer dealer is hounding me to adjust my program on all acres to include sulfur. Naturally, it’s more expensive. How do I know if sulfur will pay?
The Indiana certified crop advisers panel includes Danny Greene, Greene Ag Consulting, Franklin; Andy Like, agronomist, Amvac, Knox County; and Jeff Nagel, agronomist, Ceres Solutions Cooperative, Lafayette.
Greene: The only way to know it will pay is by participating in or conducting on-farm trials. The problem is usually a grower takes the program across their entire farm without testing it. Many don’t want to take the time to leave check strips or nontreated comparisons. Don’t find yourself with the same question next year. Test the program and use strips without sulfur to compare.
Research has shown less sulfur is deposited from the atmosphere as “free” fertilizer for crops. We have seen a decline in soil-test sulfur levels over the last 10 years. We have seen plant deficiencies, especially early in the season. While it may help across the board, the biggest return is where it is most likely to make a difference: low exchange soils and low organic matter soils.
Like: You won’t know if it’s going to pay until you do some testing on your farm using your cropping systems. I would recommend trying several different rates and sources of sulfur on corn and soybeans. A considerable amount of university work has been done showing that corn, soybeans and wheat are responsive to sulfur fertilization. It’s now your job to figure out the economics on your farm and find the products and rates that are profitable for you.
Nagel: We’ve observed more sulfur deficiencies over the past several years, confirmed by a “good” vs. “poor” tissue test. Sulfur deficiency symptoms are characterized by a lighter green color and interveinal chlorosis.
Early-season symptoms may disappear as soils warm and root systems get larger, exploring more soil volume. In other cases, symptoms persist past V5 or V6.
Past research would indicate that if deficiencies are mild and corrected before growth stage V5, either through root growth or additions of sulfur, yield loss is minimal. However, if deficiencies are moderate to severe past 21 days after emergence, yield loss could be significant. Each day sulfur is deficient past 21 days after emergence, yield loss can be 1 to 2 bushels per acre per day.
Soil tests for sulfur are generally unreliable and not very predictive. Plant analysis is the best tool.
There’s a relationship between nitrogen and sulfur that occurs in proteins at around 15-to-1. When interpreting tissue tests, both the percent sulfur concentration and N-S ratio should be assessed.
In Indiana, a tissue test of sulfur less than 0.12% and N-S ratio greater than 20-to-1 is likely deficient in sulfur. A tissue test of sulfur greater than 0.20% and N-S ratio less than 12-to-1 is likely adequate. In between those numbers, sulfur levels could be adequate or deficient.