title: Allocation of Nitrogen and Carbon Is Regulated by Nodulation and Mycorrhizal Networks in Soybean/Maize Intercropping System.
abstract: Soybean/maize intercropping has remarkable advantages in increasing crop yield and nitrogen (N) efficiency. However, little is known about the contributions of rhizobia or arbuscular mycorrhizal fungi (AMF) to yield increases and N acquisition in the intercropping system. Plus, the mechanisms controlling carbon (C) and N allocation in intercropping systems remain unsettled. In the present study, a greenhouse experiment combined with15N and13C labeling was conducted using various inoculation and nutrient treatments. The results showed that co-inoculation with AMF and rhizobia dramatically increased biomass and N content of soybean and maize, and moderate application of N and phosphorus largely amplified the effect of co-inoculation. Maize had a competitive advantage over soybean only under co-inoculation and moderate nutrient availability conditions, indicating that the effects of AMF and rhizobia in intercropping systems are closely related to nutrient status. Results from15N labeling showed that the amount of N transferred from soybean to maize in co-inoculations was 54% higher than that with AMF inoculation alone, with this increased N transfer partly resulting from symbiotic N fixation. The results from13C labeling showed that13C content increased in maize shoots and decreased in soybean roots with AMF inoculation compared to uninoculated controls. Yet, with co-inoculation,13C content increased in soybean. These results indicate that photosynthate assimilation is stimulated by AM symbiosis in maize and rhizobial symbiosis in soybean, but AMF inoculation leads to soybean investing more carbon than maize into common mycorrhizal networks (CMNs). Overall, the results herein demonstrate that the growth advantage of maize when intercropped with soybean is due to acquisition of N by maize via CMNs while this crop contributes less C into CMNs than soybean under co-inoculation conditions.
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Root Biology Center, South China Agricultural University Guangzhou, China.
authors.forename: Guihua
authors.initials: G
authors.lastname: Wang
authors.affiliation: Xinjiang Key Laboratory of Soil and Plant Ecological Processes, College of Grassland and Environmental Sciences, Xinjiang Agricultural University Urumqi, China.
authors.forename: Lichao
authors.initials: L
authors.lastname: Sheng
authors.affiliation: Xinjiang Key Laboratory of Soil and Plant Ecological Processes, College of Grassland and Environmental Sciences, Xinjiang Agricultural University Urumqi, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Zhao
authors.affiliation: Xinjiang Key Laboratory of Soil and Plant Ecological Processes, College of Grassland and Environmental Sciences, Xinjiang Agricultural University Urumqi, China.
authors.forename: Jiandong
authors.initials: J
authors.lastname: Sheng
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Root Biology Center, South China Agricultural University Guangzhou, China.
authors.forename: Xiurong
authors.initials: X
authors.lastname: Wang
authors.affiliation: Root Biology Center, Fujian Agriculture and Forestry University Fuzhou, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Liao
keywords: 13C labeling; 15N labeling; arbuscular mycorrhizal inoculation; carbon allocation; common mycorrhizal network; nitrogen transfer; rhizobium inoculation; soybean/maize intercropping