To change row spacing is a common agricultural practice to adjust plant density to enhance plant growth and development. Here we examined the fine root (≤1.0 mm in diameter) distribution and morphological characteristics of switchgrass (Panicum virgatum L.) in the 7^th growth year under three row spacing settings (20 cm, 40 cm and 60 cm) on a terrace field in the semi-arid Loess Plateau region. Roots from 0 to 150 cm soil layers were utilized to evaluate the root biomass, distribution and morphological traits in April and October 2016. Results showed that fine root biomass (FRB) mainly distributed in the 0–40 cm soil layer, and it was higher under the 20 cm and 40 cm than that under the 60 cm row spacing treatment. FRB in October was lower than in April under all three row spacings. Compared with 20 cm and 60 cm row spacing, root surface area, root length density and specific root length under 40 cm row spacing were higher, while root diameter was smaller. These conferred switchgrass with larger soil exploration and root-soil interface. It implied that switchgrass grown under 40 cm row spacing had stronger ability on exploiting soil resources in the semi-arid area.

改变行距是调整植物密度以增强植物生长和发育的常见农业实践。在这里，我们检查了细根（≤1.0毫米直径）分布和柳枝稷的形态特征（柳枝稷在7 L.）^个在半干旱黄土高原地区的梯田上，在三行间距设置（20 cm，40 cm和60 cm）下生长的年份。利用2016年4月和2016年10月从0到150 cm土层的根来评估根的生物量，分布和形态特征。结果表明，细根生物量（FRB）主要分布在0-40 cm的土层中，并且较高在20 cm和40 cm下比在60 cm行间距处理下要好。在所有三个行间距下，10月的FRB均低于4月。与20 cm和60 cm行距相比，40 cm行距下的根表面积，根长度密度和比根长较高，而根径较小。这些使柳枝with具有更大的土壤探测性和根-土界面。