Nitrogen acquisition, fixation and transfer in maize/alfalfa intercrops are increased through root contact and morphological responses to interspecies competition

• 作者: SHAO Ze-qiang ZHENG Cong-cong Johannes A.POSTMA LU Wen-long GAO Qiang GAO Ying-zhi ZHANG Jin-jing
• 来源期刊: 农业科学学报（英文版）
• 年，卷（期）: 2021,（8）
• 所属期刊栏目: Agro-Ecosystem & Environment
• 页码范围: 2240-2254
• 页数: 15页
• 语种: 英文
• DOI: 10.1016/S2095-3119(20)63330-5

摘要

Nitrogen (N) fixation by legumes and nitrogen transfer to cereals have been considered as important pathways for overyielding and higher N use efficiency in cereal/legume intercropping systems. However, the extent to which root morphology contributes to N fixation and transfer is unclear. A two-factorial greenhouse experiment was conducted to quantify the N fixation, transfer and root morphology characteristics of the maize/alfalfa intercropping system in two consecutive years using the 15N-urea leaf labeling method, and combining two N levels with three root separation techniques. N application could inhibit N fixation and transfer in a maize/alfalfa intercropping system. Irrespective of the N application level, compared with plastic sheet separation (PSS), no separation (NS) and nylon mesh separation (NNS) significantly increased the total biomass (36％) and total N content (28％), while the N fixation rate also sharply increased by 75 to 134％, and the amount of N transferred with no root barrier was 1.24–1.42 times greater than that with a mesh barrier. Redundancy analysis (RDA) showed that the crown root dry weight (CRDW) of maize and lateral root number (LRN) of alfalfa showed the strongest associations with N fixation and transfer. Our results highlight the importance of root contact for the enhancement of N fixation and transfer via changes in root morphology in maize/alfalfa intercropping systems, and the overyielding system was achieved via increases in maize growth, at the cost of smaller decreases in alfalfa biomass production.