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 deficiencies on winter rye growth and root architecture 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 and topsoil root biomass, number of tillers, nodal root number, root angle, root length density (RLD), specific root length (SRL), and root diameter were assessed at five growth stages. Results. We found that that grain yield, shoot, and root biomass were highest in the NPKCa + m + s treatment and lowest under N omission. Around flowering, a trend for an enhanced root number in the N and P omission treatments was observed. At the same sampling date, the NPKCa + m + s treatment showed significantly higher SRL than the P omission treatment. The RLD increased for all treatments from date 1 to 4, with NPKCa + m + s and N omission treatments showing the highest and lowest RLD, respectively. At the onset of stem elongation, N and P omission led to a significant reduction in average root diameter, P omission promoted higher tiller number and N omission caused steeper root angles. Conclusions. These findings demonstrate the strong impact of management, environment and developmental stage on root phenotypic plasticity.