Deep Rooting as an Indicator of Deep Soil Water and N Uptake in Potato (Solanum tuberosum L.)

Abstract Breeding for potato deep roots can increase water and nitrogen uptake by potatoes and it can be an option to maintain stable yields with decreased inputs. This study investigates the relationship between potato root characteristics, water stress resistance and deep soil nitrogen uptake, accessing variations among cultivars and nitrogen fertilization levels. Thirteen potato cultivars were grown during 2018 and 2020 at a semi-field root phenotyping platform in Denmark. Root growth was monitored via minirhizotron tubes down to 1.8 m soil depth. Drought treatment started in the mid-June and deep soil nitrogen uptake was tracked via 15 N isotope application at 1.3–1.4 m soil depth during tuber formation. Water stress resilience was identified using 13 C natural discrimination process in plants. Tuber samples were analyzed for 15 N and 13 C content. While drought affected potato yield (not always significantly), it did not affect nitrogen uptake. Root length and distribution varied among varieties, with deeper roots (down to 1.30 m) observed in August. Statistical differences ( p < 0.05) in root length, yield and nitrogen uptake were found among varieties. Cultivars with longer growing season exhibited larger, deeper roots and increased nitrogen uptake from deep soil. High correlation (R = 0.8) between deep roots and 15 N uptake was observed for all varieties. Deeper roots are contributing to deep soil nitrogen uptake, but 13 C content in tubers is not a reliable indicator of water stress resilience. Despite this, the study suggests the potential for breeding potatoes with deep roots to achieve stable yields, considering differences in water and nitrogen uptake among varieties.