Nevada County Picayune and Gurdon Times Newspaper Archive

Nitrate, Sulfate Needed

by C. RICHARD MAPLES

Extension Specialist --

Agricultural Communications

Heavy rains this winter and spring have robbed some fields of the nitrate and sulfate needed for crop development, according to Dr. Mike Daniels, agronomist for the Cooperative Extension Service, University of Arkansas.

"On our heavier soils with poor internal drainage, a lot of nitrate may be lost to denitrification," said Daniels. "Denitrification is a loss of nitrate as a gas, usually over a long period of time. The warm, wet weather in March was perfect for the bacterial activity that causes denitrification.

"We're also concerned about the leaching of nitrate down into the soil profile, especially in sandy soils," Daniels said. "And the same is true for sulfate. Water carries sulfate downward just like nitrate in our sandier soils."

A routine soil sample may not reflect the true nitrate and sulfate levels if the nutrients have been leached down into the soil. "We highly recommend that cotton farmers take a subsoil sample, down to 30 inches, to determine how much nitrogen is present in the soil profile," said Daniels.

"Cotton and most other crops are going to receive nitrogen fertilizer anyway, but it wouldn't hurt to apply 100 pounds of ammonium sulfate on sandier soils," said the agronomist. "You'll supply 24 pounds of sulfate, which is more than adequate. Plus, you can count the 21 pounds of nitrate in 100 pounds of ammonium sulfate as credcit toward your total nitrogen needs."

Daniels said leaching has caused sulfur deficiencies in wheat fields across the state this spring, even in silt loam soils where sulfur usually isn't a problem. Unfortunately, it's probably too late to salvage wheat with an ammonium sulfate application.

Lack of sulfate is also a concern for corn and grain sorghum grown on lighter textured soils. The rain may leach sulfate deep into the soil profile where it's not available to plant roots. "That sulfur may become available later on, but we recommend that you apply the 100 pounds of ammonium sulfate as a precaution," said Daniels. "It won't cost you much more."

For more information about crop fertilization, contact your county office of the Cooperative Extension Service, University of Arkansas.