Effects Of Water And Nitrogen Regimes On Growth And Relative Competivity Of Old World Bluestem And Switchgrass Under Intrcropping

In order to clarify the growth of old world bluestem(Bothriochloa ischaemum, B) andswitchgrass (Panicum virgatum, P) and their relative competivity under different water andnitrogen regimes, one pot experiment was conducted using a replacement series design inwhich old world bluestem and switchgrass were sowed at five ratios(8:0,6:2,4:4,2:6,0:8)under two water regimes(well-watered, WW:80%FC and water-stressed, WS:40%FC) andtwo nitrogen regimes(N0, adding0mg N Kg-1and N1, adding100mg N Kg-1). We investigatedand compared the gas exchange parameters, leaf SPAD, chlorophyll fluorescence kineticparameters, plant height, leaf length, leaf width, tiller number, water consumption andbiomass of of old world bluestem and switchgrass across growth periods (tillering period,heading period and mature period), and calculated the relative competivity of old worldbluestem and switchgrass based on biomass production. The main conclusions were asfollows:1) Both old world bluestem and switchgrass had strong drought resistance. Comparedwith old world bluestem, switchgrass had higher Pn, Gs, Tr, leaf SPAD andnon-photochemical pathway to protect photosynthetic appatatus, while lower WUELandphotochemical pathway to use lihgt. Photosynthetic ability of old world bluestem andswitchgrass could be improved by adding water or nitrogen, and it was the best when waterand nitrogen was enough.2) Compared with old world bluestem, switchgrass had smaller plant height and totalbiomass, bigger leaf width, root:shoot ratio and WUE. The gowth of old world bluestem andswitchgrass improved significantly by adding water or nitrogen, and they grew best whenwater and nitrogen was enough. The shoot biomass, root biomass and total biomass of oldworld bluestem and switchgrass decreased as their propotion in the mixture decreased,respectively.3) When water and nitrogen was limited, old world bluestem was the dominat species inB2P6and B4P4, while the competitvity of old world bluestem and switchgrass was equal inB6P2, there was strong antagonism between old world bluestem and switchgrass in the shootbiomass, root biomass and total biomass. As the addition of nitrogen, the root competivity ability of switchgrass increased significantly and the antagonistic effect of shoot between oldworld bluestem and switchgrass decreased. Switchgrass became the domiant species in B6P2when water and nitrogen was enough.