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Acta Prataculturae Sinica ›› 2021, Vol. 30 ›› Issue (8): 73-85.DOI: 10.11686/cyxb2021037

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Nitrogen utilization and interspecific feedback characteristics of intercropped alfalfa/oat with different root barriers

Xue WANG(), Xiao-jing LIU(), Ya-jiao ZHAO, Jing WANG   

  1. College of Pratacultural Science,Gansu Agricultural University,Key Laboratory of Pratacultural Ecosystem,Ministry of Education,Pratacultural Engineering Laboratory of Gansu Province,Sino-US Center for Grazingland Ecosystem Sustainability,Lanzhou 730070,China
  • Received:2021-01-26 Revised:2021-03-08 Online:2021-07-09 Published:2021-07-09
  • Contact: Xiao-jing LIU

Abstract:

In this study, we explored the effects of root barriers on interspecific nitrogen competition and mutual feeding in an alfalfa/oat intercropping system using a bucket soil culture method. The nitrogen metabolism characteristics and root characteristics of alfalfa and oat plants, as well as the nodulation characteristics of alfalfa plants, were investigated at different growth stages, under two different nitrogen levels, and with different root barriers. The root barrier treatments could be ranked, from highest to lowest values of nitrogen metabolism characteristics and root characteristics of oat, nodulation of alfalfa at different growth stages, and nitrogen levels, as follows: No barrier>nylon mesh barrier>plastic barrier≥monoculture, and the differences among these treatments were significant. The activities of nitrogen metabolism enzymes, the nitrogen concentration, and nitrogen accumulation in alfalfa in the budding stage and initial blooming stage were significantly higher in the monoculture treatment than in the no barrier and nylon mesh barrier treatments (P<0.05). The root barrier treatments could be ranked, from largest to smallest root average diameter and root volume across all growth stages and nitrogen levels, as follows: Monoculture>plastic barrier>nylon mesh barrier>no barrier. The root average diameter and root volume were significantly higher in the monoculture treatment than in the no barrier treatment. The activities of nitrogen metabolism enzymes, dry weight, nitrogen concentration, nitrogen accumulation, root surface area, root average diameter, root volume, and root activity of alfalfa and oat at different growth stages were higher in the N210 (nitrogen application) treatment than in the N21 treatment (no added nitrogen). The total nodule weight, total nodule number, effective nodule number, and effective/nodule number of alfalfa were lower in the N210 treatment than in the N21 treatment. Therefore, in the alfalfa/oat intercropping system, closer interspecific root interactions are conducive to oat root growth and root activity, nitrogen assimilation by oat, nodulation and nitrogen fixation by alfalfa, and transfer of nitrogen from alfalfa to oat. Such conditions can enhance the complementary utilization of nitrogen by both species, and improve the feedback of interspecific nitrogen nutrition in the alfalfa/oat intercropping system. These results show that closer interspecific root interactions can effectively improve nitrogen-use efficiency in this intercropping system. These findings also show that the addition of nitrogen at an appropriate dose to promote growth at the early period can strengthen the interspecific root interaction and the complementary utilization of nitrogen, thereby improving nitrogen-use efficiency in this intercropping system.

Key words: alfalfa, oat, intercropping, root barriers, nitrogen mutual feeding characteristics