Nitrogen

Abstract

Field experiments were undertaken to develop improved strategies for applying N fertilizer to rain‐fed spring wheat grown in South Australia. At most sites broadcasting N fertilizer during early tillering was as effective as drilling equivalent rates of N at sowing. Split applications were another effective strategy. Plant tests for confirming and predicting N deficiency were also assessed. The concentration of nitrate‐N (NO₃‐N) in basal stems was the most suitable test for defining N status in wheat during tillering, and for predicting grain yield responses to applied N. Criteria at near maximum yield decreased with advancing plant age. Nitrogen and NO3‐N concentrations in the youngest emerged leaf blade were less suitable plant tests. A rapid plant N test was also developed. An improved strategy for diagnosing and correcting N deficiency in wheat is suggested.

Key words:

• Wheat
• nitrogen fertilizer
• plant analysis
• plant nitrate
• rapid plant test