Effect of urea and ammonium nitrate in top-dressing application on corn yield under no-till system

Abstract

To evaluate the efficience of nitrogen (N) sources and time of N application on corn yield, a field
experiment was carried out in a Typical Red Latosol (oxisol) in Chapecó, Santa Catarina State, Brazil. The
experiment was conducted as completely randomized block design with the use of two top-dressed N sources (urea and ammonium nitrate) and four application time (total dose at plant emergence, 1/3 at emergence and 2/ 3 28 days later, and total dose at 14 and 28 days after plant emergence), plus an additional treatment without N
fertilization. The results showed that only the time of N application had influence on corn yield. Best results
generally were obtained when total N dose was applied at plant emergence or when applied 1/3 of the total N at plant emergence and the remaining 28 days later. The source of N did not significantly affect corn yield. Since no significant differences were observed in the corn yield, the decision of using urea or ammonium nitrate for topdress application should be based on the cost per unity of N