Influence of Inoculant Form and Applied Nitrogen on Growth and Root Nodulation of Maackia amurensis

Abstract

Abstract We studied growth and nodulation of Maackia amurensis Rupr. & Maxim, treated with three forms of an inoculant of Bradyrhizobium (USDA 4349) and irrigated with solutions containing N at 1.8, 3.6, 7.2, or 14.3 mol·m−3(25, 50, 100, or 200 ppm). One inoculant (arabinose-gluconate liquid) was prepared in our laboratory, whereas the other two (Cell-Tech liquid and Cell-Tech peat powder) were obtained from a commercial source. Nodule dry mass of 10-week-old seedlings was similar regardless of inoculant form. Only plants supplied N at 1.8 and 3.6 mol·m−3 (25 and 50 ppm) nodulated consistently, and nodule dry mass of plants in these two treatments was not different. Laminar area and plant dry mass were highest among plants provided the two highest concentrations of N. Shoot N content was lowest and highest for plants provided N at 3.6 mol·m−3 (50 ppm) and 14.3 mol·m−3 (200 ppm), respectively, and it was not affected by form of inoculant. We conclude that liquid and peat-based inoculants cause a similar degree of nodulation. This study also demonstrated that providing N at concentrations of 7.2 mol·m−3 (100 ppm) or higher inhibits nodulation, and that inoculation with USDA 4349 does not substitute for applied N if maximal early seedling growth is desired.