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Acta Prataculturae Sinica ›› 2024, Vol. 33 ›› Issue (3): 85-96.DOI: 10.11686/cyxb2023143

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Root and carbon-nitrogen metabolism characteristics of alfalfa-oat mixed stands under continuous intercropping

Xue WANG(), Xiao-jing LIU(), Jing WANG, Yong WU, Chang-chun TONG   

  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:2023-04-29 Revised:2023-06-05 Online:2024-03-20 Published:2023-12-27
  • Contact: Xiao-jing LIU

Abstract:

This research investigated the root growth characteristics, carbon and nitrogen metabolism characteristics, and the long-term effects of their coupling mechanisms under continuous leguminous-gramineous forage intercropping. A field frame planting, soil culture experiment was conducted to study the root characteristics, carbon and nitrogen metabolism characteristics, and their mutual co-ordination of alfalfa (Medicago sativa)-oat (Avena sativa) intercropping for two consecutive years after planting. Alfalfa monoculture and oat monoculture crops were used as a reference. It was found that the biomass of intercropped oats was significantly higher than monoculture oats (P<0.05). The root surface area and root average diameter of intercropped oats were significantly higher than monoculture oats (P<0.05). The transpiration rate (Tr), net photosynthetic ratePn), stomatal conductance (Gs), ribulose-1,5-bisphosphate carboxylase (RuBPCase) activity, the activities of four nitrogen metabolism enzymes, and carbohydrate accumulation of intercropped oats were significantly higher than monoculture oats (P<0.05), while alfalfa showed an opposite trend. Correlation analysis found that the biomass was positively correlated with photosynthetic gas exchange parameters, nitrogen metabolism enzyme activities and root characteristics. Root surface area and root average diameter were significantly positively correlated with TrPnGs, nitrate reductase (NR) activity, nitrogen accumulation, and total protein content (P<0.05). Root volume, root surface area, and root average diameter were highly significantly positively correlated with nitrate reductase activity and glutamate synthase activity (P<0.01). Thus, the intercropping of alfalfa and oat is more conducive to optimizing the root morphology of oat, while also significantly increasing the net photosynthetic rate and transpiration rate of oat, enhancing the activities of carbon and nitrogen metabolism enzymes such as RuBPCase, NR, and glutamine synthetase in oat, thereby promoting the accumulation of carbohydrate and protein to improve oat biomass and quality. Continuous intercropping weakened the inhibition of root surface area and root volume of alfalfa within the system, and expanded the total root length of alfalfa, but overall, intercropping inhibited root growth and carbon-nitrogen metabolism, which was not conducive to the accumulation of its metabolites and biomass. Moreover, total root length, root surface area, and root volume significantly promote carbon-nitrogen metabolism, the improvement of root system and carbon-nitrogen metabolism in the alfalfa/oat intercropping system effectively increased the biomass and total protein content in the system.

Key words: alfalfa, oat, continuous intercropping, root characteristics, carbon and nitrogen metabolism characteristics