Nitrogen Acquisition and Allocation Traits in Peanuts with Different Nodulation Efficiency Revealed by the 15N Tracer Analysis

The study aims to evaluate the difference of nitrogen (N) utilization in peanut varieties with different nodulation efficiency and the contribution of different N sources to yield formation. Based on an outdoor pot experiment, 15N isotope-labeled urea was used as a N source to investigate the effects of different N fertilization levels (N rates with 45, 75, 105, 135, 165 kg N ha–1, defined as N45, N75, N105, N135 and N165 in the study, respectively) on peanut photosynthesis, photosynthate accumulation, yield, and N distribution and transport. The results showed that N application can improve peanut yield by creating photosynthesis, dry matter weight, and N accumulation, and the N105 treatment had the most significant effect. However, higher N applications inhibited the number of peanut root nodules. The ratio of N supply for peanuts from nodules, soil, and fertilizer at the pod setting stage was about 5:3:2, and the ratio of fertilizer distribution for low nodulation peanut variety of reproductive organ (pod) to nutrient organs (root, stem, leaf) was about 3:2, while the high nodulation variety was about 1:1. Biological N fixation is an important N source during peanut growth and development. Appropriate N fertilizer can further promote peanut growth and yield formation without inhibiting nodulation and N fixation. In agricultural production, optimizing N fertilizer management (105 135 kg N ha–1) in combination with using nodulation efficient peanut varieties not only promotes the N-cycling in agriculture, but also effectively reduce the waste of N fertilizer as well as environmental damage.