Symbiotic performance,shoot biomass and water-use efficiency of three groundnut(Arachis hypogaea L.)genotypes in response to phosphorus supply under field conditions in Ethiopia

摘要

Phosphorus is a key nutrient element involved in energy transfer for cellular metabolism,respiration and photosynthesis and its supply at low levels can affect legume nodulation,N2 fixation,and C assimilation.A twoyear field study was conducted in Ethiopia in 2012 and 2013 to evaluate the effects of P supply on growth,symbiotic N2 nutrition,grain yield and water-use efficiency of three groundnut genotypes.Supplying P to the genotypes significantly increased their shoot biomass,symbiotic performance,grain yield,and C accumulation.There was,however,no effect on shootδ13C values in either year.Compared to the zero-P control,supplying 40 kg$ha–1 P markedly increased shoot biomass by 77%and 66%in 2012 and 2013,respectively.In both years,groundnut grain yields were much higher at 20 and 30 kg$ha–1 P.Phosphorus supply markedly reduced shootδ15N values and increased the%Ndfa and amount of Nfixed,indicating the direct involvement of P in promoting N2 fixation in nodulated groundnut.The three genotypes differed significantly inδ15N,%Ndfa,N-fixed,grain yield,C concentration,andδ13C.The phosphorusgenotype interaction was also significant for shoot DM,N content,N-fixed and soil N uptake.