AUTHOR=Sun Zhengguo , Yi Mingxuan , Liu Xinbao , Yixin Shen , Li Jianlong 

TITLE=Synergism Between Water Management and Phosphorus Supply Enhances the Nodulation and Root Growth and Development of Chinese Milk Vetch (Astragalus sinicus L.)

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 12 - 2021

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.784251

DOI=10.3389/fpls.2021.784251

ISSN=1664-462X

ABSTRACT=The response of root development and nodule formation of the manure crop Chinese milk vetch to different levels of soil moisture and phosphorous (P) fertilizer remains unclear. In this study, a pot experiment was performed to trace the root growth and nodule formation of Chinese milk vetch during the growth stages, under various soil moisture gradients (25% [W1], 50% [W2], 75% [W3], and 100% [W4] of the maximum field water-holding capacity) and P levels (0 [P0], 30 [P1], 60 [P2], and 90 [P3] kg hm−2). The root/shoot ratio, root vitality, number of nodules, nodule weight, and nitrogenase activity were affected remarkably by soil moisture across the whole stage (<0.01). The root/shoot ratio at the seedling stage was affected significantly (P<0.05), and the other indices at the seedling stage and all the indicators at the branching and flowering stages were influenced substantially by the level of added P (P<0.01). Differences were found in the interaction effect between soil moisture and added P on the characteristic indices of the root and nodule at the different growth stages. However, no significant differences were observed in the root/shoot ratio, number of nodules, and nodule weight at the seedling stage (P>0.05), but significant differences were observed in the root vitality and nitrogenase activity (P<0.01). Significant differences were also found in the root/shoot ratio, number of nodule, nodule weight (P<0.05), root vitality, and nitrogenase activity (P<0.01) at the branching stage. The following results were observed at the full-flowering stage: all indices showed extremely significant differences (P<0.01); W1P0 and W2P0 showed the highest root/shoot ratio; W2P2 and W3P2 resulted in the highest root activity; W3P3 and W3P2 had the highest number and weight of nodules; and W3P2, W2P2, and W3P1 had higher nitrogenase activity than the other treatments. The application of P at 60 kg hm−2 and the relative soil moisture of 75% was the best P–water combination suitable for the root development, nodule formation, and nitrogen fixation of Chinese milk vetch. This study will provide a theoretical basis for the production of this plant by managing the synergistic interaction between P fertilizer and soil moisture.