N Sources Affect Growth, Nutrient Content, and Net Photosynthesis in Mate (Ilex paraguariensis St. Hil.)

摘要

The influence of different N sources on the growth of mate (Ilex paragurariensis St.Hil.) seedlings grown in greenhouse was studied. All seedlings received a base fertilization of 10 mg N.kg~(-1) soil as NH_4NO_3, 60 mg P_2O_5 and 40 mg K_2O kg~(-1) soil as KH_2PO_4 15 days before treatments application. Treatments were as follow: Control, with no extra N added; Urea = 700 mg N.kg~(-1) soil as Urea; NO_3~- = 100 mg N.kg~(-1) soil as Ca(NO_3)_2; and NH_4~+ = 100 mg N.kg~(-1) soil as (NH_4)_2SO_4. It was concluded that: 1) increasing N content in leaves alone was not able to promote gain in biomass production of mate seedlings; 2) seedlings receiving N-NH_4 showed a higher accumulation of P and Mg on shoot biomass; and 3) an increase in leaf area, leaf number and net photosynthesis observed at the N-NH_4 treatment was coincident with an increasing absorption of P and Mg.