Winter rye root growth and plasticity in response to nitrogen and phosphorus omission under field conditions

Aims We investigated the effects of N and P omission on winter rye growth and root traits under field conditions. Methods Sampling was conducted during the 2022 season at the long-term fertilizer experiment Dikopshof, Germany. Four fertilizer treatments were chosen: (1) fully fertilized including manure (m) and supplemental mineral fertilizer (s) (NPKCa + m + s), (2) fully fertilized without manure (NPKCa), (3) N omitted (_PKCa), and (4) P omitted (N_KCa). Shoot biomass, number of tillers and root traits: topsoil root biomass, nodal root number, root angle, root length density (RLD), specific root length (SRL), and root diameter were assessed at five growth stages from tillering to flowering. Results Shoot and root biomass showed significant interaction between fertilizer treatments and sampling date. The NPKCa + m + s treatment led to the highest shoot biomass up to early boot stage. Around flowering the nutrient omission treatments resulted in the lowest shoot biomass compared with the NPKCa + m + s treatment. In contrast, root biomass showed non-significant differences among treatments at the beginning of the growing season and around early boot stage. All other root traits showed a non-significant interaction between fertilizer treatments and sampling dates, and while there was a significant impact of sampling dates, fertilizer treatments often led to non-significant differences. The N and P omission treatments showed the lowest RLD. Conclusions These findings demonstrate the strong impact of nutrient omission and developmental stage on shoot and root growth of winter rye.