There are Different Pathways to Stable Spring Wheat Grain Yield and Nitrogen Utilization Efficiency in Conventional and Organically‐Managed Systems

Abstract

The high costs and negative environmental impact associated with the use of N in crop production suggest we need to improve our knowledge of crop N utilization efficiency (NUtE: the amount of grain produced per unit of N uptake). We conducted a study in organic and conventional fields to compare the effect of management and genetic variability for grain yield and NUtE in spring wheat (Triticum aestivum L.). We also assessed the relationships between yield and NUtE stability among tested cultivars under organic management. Grain yield and NUtE were 50 and 20% less in organic compared to conventional management (1.62 and 3.27 t ha−1 for grain yield and 16.2 and 20.9 t DM t−1 N for NUtE, respectively). Analyses of variance revealed significant effects of genotype (G), environment (E) (year × location), and G × E interactions on grain and NUtE in organic environments. Traits in the organic system that were sensitive to G × E interactions included grain yield, harvest index (HI), NUtE, and dry matter production. Four modern cultivars with differing genotypic characteristics (medium tall stature, disease and pest resistant, and semi‐dwarf), had high and stable grain yield, and NUtE in both systems. Our results suggest that the modern wheat cultivars CDC Kernen, CDC Stanley, Carberry, and Unity may be suitable for organic systems because of their stable yield and NUtE across tested environments. Such characteristics could be advantageous under organic farming systems where temporal and spatial variations of resources are normally greater than conventional systems.Core Ideas Nitrogen utilization efficiency has gentotype × environment interactions in organic fields. Low harvest index in organic systems indicates reduced assimilate partitioning due to weed competition. Four modern cultivars with different traits exhibited consistent grain yield in organic systems. Different traits in the four cultivars may be key for organic crop production.