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

doi:10.1016/S2095-3119(20)63330-5

摘要/Abstract

摘要：

豆科植物的氮固定及其向禾本科植物的氮转移被认为是禾本科/豆科间作系统增产和氮素高效利用的一种重要途径。然而间作作物的根系形态变化对氮固定和氮转移的贡献尚不清楚，本研究通过连续两年的双因素（两个氮水平，三种根系分隔方式）温室实验，运用15N同位素标记技术测定了玉米/紫花苜蓿间作系统的氮素固定，氮素转移以及根系形态特征变化。研究结果表明，施氮显著抑制了玉米/紫花苜蓿的氮素固定和转移。不考虑施氮水平，与塑料膜分隔相比，尼龙网分隔和不分隔处理使总生物量和总吸氮量分别提高了36%和28%，同时使氮素固定率显著升高了75-134%；不分隔处理的间作系统氮素转移量是尼龙网分隔处理的1.24-1.42倍。冗余度分析(RDA) 表明玉米冠根干重和苜蓿侧根数量与间作氮素固定和转移的相关性最强。我们的研究强调了根系接触和根系形态变化对增强玉米/紫花苜蓿间作系统的氮素固定与转移的重要性，这种间作系统产量的增加是通过较大的促进玉米生长，同时以降低一小部分苜蓿的生长为代价来实现的。

Abstract:

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.

Key words: maize/alfalfa intercropping , nitrogen fixation and transfer , root morphology , nitrogen utilization

. [J]. Journal of Integrative Agriculture, 2021, 20(8): 2240-2254.

SHAO Ze-qiang, ZHENG Cong-cong, Johannes A. POSTMA, LU Wen-long, GAO Qiang, GAO Ying-zhi, ZHANG Jin-jing. Nitrogen acquisition, fixation and transfer in maize/alfalfa intercrops are increased through root contact and morphological responses to interspecies competition[J]. Journal of Integrative Agriculture, 2021, 20(8): 2240-2254.

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