Rentech Nitrogen Partners LP posted a fourth-quarter loss of $17.4 million on sales of $54.6 million compared to a year-ago net income of $17.6 million on sales of $92.4 million. Rentech cited lower volumes due to scheduled and unscheduled downtime at its East Dubuque and Pasadena plants as well as weaker nitrogen prices. Full-year net income sank to $4.1 million on sales of $311.4 million down from the year-ago $107 million and $261.6 million, respectively.