NITROGEN CONCENTRATION AND PROPORTION OF NH4-N AFFECT POTATO CULTIVARRESPONSE IN SOLID AND LIQUID-MEDIA()

Potato (Solanum tuberosum L.) cultivar performance in relation to the proportions of N supplied by NH4+ and N concentrations was studied in solid and liquid culture media. Ammonium ion was supplied as 0%, 30%, 50%, or 100% of the total N for 'Spunta', 'Kennebec', and 'Huinkul', a nd two N concentrations (30 and 60 mM) for the 'Spunta'. The cultivars differed in sensitivity to the NH4+ : NO3- ratio, 'Spunta' showing th e most and 'Huinkul' the least sensitivity, Decreasing the ratio in th e medium increased carbon use, as reflected by dry matter accumulation . When the concentration of N used in Murashige and Skoog medium was r educed by half, shoot length, number of nodes, and dry mass were impro ved in 'Spunta', in both solid and liquid media, due to an enhancement of carbon use.