Arkansas rice producers can spend as much as $85 an acre to fertilize fields, highlighting the need for growers to use the best management practices possible.

Nitrogen is the costliest item in a grower's fertilizer budget. It can cost more than $40 an acre with application costs. The exact cost depends on the current price of urea.

“The primary focus of nitrogen research is to optimize management efficiency by evaluating nitrogen rates, timing and fertilizer sources,” said Chuck Wilson, rice specialist with the University of Arkansas Cooperative Extension Service at the Rice Research and Extension Center. “We conduct studies evaluating these factors in association with different varieties and soil types to obtain the best yield with the least amount of fertilizer.”

“All counties use the nitrogen research we conduct,” Wilson said, “because management of nitrogen is so critical for the best yields.”

Other ongoing studies examine the effects nitrogen has on rice plants. Effectively managing nitrogen fertilizer presents the greatest challenge to rice producers, said Rick Norman, agronomy professor at the UA Agricultural Experiment Station in Fayetteville, Ark.

“No other nutrient requires as much detailed management attention as nitrogen fertilizer,” Norman said. “No other nutrient can deliver greater benefits in increased rice grain yields for effective management.

“We expend so much effort to determine the proper nitrogen fertilizer rate for each new rice variety prior to its release,” Norman said.

Phosphorus research has focused on refining soil test parameters for making phosphorus recommendations and evaluating optimum fertilizer timing.

“Based on phosphorus research over the past five-plus years, we recommend phosphorus on soils with high pH and low soil test phosphorus,” Wilson said.

Much of the phosphorus work has been done in Cross and Poinsett counties in northeast Arkansas.

“What we've seen is that the phosphorus levels are more critical to good rice production than potash,” said Rick Wimberley, Cross County Extension staff chair. “What we've done in the last three years has been to look at the application timing of phosphate. Traditionally, producers apply it before planting. What we've seen is that phosphate applied in the pre-flood situation remains more available to the plant.”

Nathan Slaton, UA assistant professor in soil testing, said that in 2003 research to investigate the response of rice grown on clay soils to zinc fertilization was initiated in six grower fields in Jefferson, Poinsett and St. Francis counties and two experiment stations at Keiser (Mississippi County) and Rohwer (Desha County).

Results show that the availability of zinc on silt and sandy loam soils is known to decrease as soil pH increases, especially when soil pH is greater than 7.0.

Results from 2003 are only preliminary, and additional data is needed from many other fields to determine whether observations made in 2003 can be consistently repeated and final zinc fertilizer recommendations can be developed for rice grown on clay soils.