Durum wheat yield and protein influenced by nitrogen management and cropping rotation

Abstract

Nitrogen (N) is the major input for cereal grain production. N management in durum wheat (Triticum turgidum subsp. durum) is critical for optimizing grain yield, protein concentration, and utilization efficiency of nitrogen fertilizer. A two-year study was conducted in the semi-arid region of the US Northern Great Plains (NGP) to investigate nitrogen input levels and application methods under fallow-durum and pea-durum systems. A durum wheat (cv. Joppa) was planted in the field following fallow or field pea with N input levels of 65 and 135 kg ha−1 and four application methods for each N input level. Results showed that water was the major limiting factor determining grain yield and protein concentration. Grain yield was greater but with similar protein concentration following fallow (1958 kg ha−1, 16.7%) than following field pea (1754 kg ha−1, 16.4%). Increasing N input from 65 kg ha−1 to 135 kg ha−1decreased grain yield from 1933 to 1779 kg ha−1 but improved protein concentration from 16.3 to 16.8%, which resulted in a negative nitrogen use efficiency (NUE). Application method of N did not significantly affect yield and protein, but there was a trend of yield increase via split application of N at the lower rate in a wetter year. The drought in 2017 resulted in lower test weight and harvest index (HI). The HI was lower in the135 kg ha−1 N rate than in the 65 kg ha−1 N rate, especially in the dryer year. Excessive N inputs in a water-limited environment may result in ‘haying-off’.