Agropyron mongolicum Keng’s Growth in Response to Nitrogen Addition Is Linked to Root Morphological Traits and Nitrogen-Use Efficiency

Abstract

Nitrogen (N) is an essential macronutrient for plant development and growth, and increased N deposition is affecting the diversity and productivity of plants. The objective of this study was to explore the growth response of Agropyron mongolicum Keng to N addition and to determine whether N-induced changes in soil-available nutrients have indirect impacts on the biomass of A. mongolicum via the regulation of root morphological traits and NUE. We conducted a pot experiment subjecting A. mongolicum to five N addition levels (0, 0.8, 1.6, 2.4, and 4.0 g N m−2 yr−1) under greenhouse conditions. N was provided through urea [CO(NH2)2] delivered with two equal applications and added at the seeding and tillering stages. The results showed that the total biomass response of A. mongolicum to increasing N addition appeared unimodal-shaped with an N saturation threshold at 3.20 g N m−2 yr−1. The total biomass was significantly and positively correlated with the root surface area (RSA), volume (RV), length (RL), forks number (RF), N-uptake efficiency (NUpE), and N-utilization efficiency (NUtE) (p < 0.05). N-induced changes in soil-available nutrients had an indirect impact on the total biomass of A. mongolicum via the regulation of root morphological traits and NUE.

Nitrogen fertilization and CO2 concentration synergistically affect the growth and protein content of Agropyron mongolicum

“…Twice a month during the treatment period, each pot in OTCs received N fertilizer dissolved in 500 mL of tap water by spraying the seedlings in four equal splits at rates of total NH 4 NO 3 -N of 0, 1.2, and 3.6 g N m −2 yr −1 on 15th, 30th June, 15th, 30th July 2021, respectively. N application rates were designed based on our previous study ( Xu et al, 2022 ). All pots were rotated every 7 days between the chambers to prevent the potential position effects and regularly weighed, watered, and maintained at 70–80% of field capacity until the end of the experiments.…”

“…Fresh root samples from each treatment were analyzed for total root length (TRL) and surface area (RSA), the method of determination as described in a previous study by Xu et al (2022) . Specific root length (SRL) was calculated by dividing TRL by its mass ( Cohen et al, 2019 ).…”