Fine root morphology and growth in response to nitrogen addition through drip fertigation in a Populus × euramericana “Guariento” plantation over multiple years

Context: Nitrogen (N) deficiency is common in forest soils, and N addition is increasingly applied to the cultivation of plantations. Knowledge of the potential effect of high-efficiency fertilization techniques based on successive field experiments on fine root morphology and growth in trees with respect to nutrient acquisition strategy is insufficient.

Aim: We aimed to quantitatively investigate the responses of fine roots in morphology and growth to N addition through surface drip fertigation (DF) over multiple years in a Populus × euramericana “Guariento” plantation.

Methods: A field experiment that included four DF treatments with N addition levels (0, 60, 120, and 180 kg N ha-1 yr-1) was conducted for three successive years. A coring method was used to sample soils and quantify root morphological traits, foraging precision, and soil N content along 0-60 cm profiles.

Results: The distribution pattern of fine roots along a vertical profile was not affected by the DF treatme...