Nitrogen nutrition of potato cultivars differing in maturity

In potato, dry matter (DM) production and partitioning between plant organs and N accumulation are affected by N application; however, since cultivars differ in these processes, N fertilization must be adjusted to each cultivar. This paper studies the response of potato cultivars differing in maturity to N fertilization in the south-east of the Buenos Aires Province (37 degrees 45'S, 58 degrees 18'W) in two growing seasons. Treatments combined four N doses (0-180 kg ha(-1)) and four cultivars: Jaerla (early), Spunta (mid-early), Mailen INTA (medium late) and Huinkul MAG (late). DM and N content were measured in leaves, stems and tubers throughout the growing season and intercepted photosynthetically active radiation was regularly assessed. There was an increase in tuber yield up to intermediate N doses (60 kg ha(-1) in 1990 and 120 kg ha(-1) in 1991). Tuber yield was similar for Spunta and Huinkul MAG. There was no interaction between cultivar and N fertilization for tuber dry matter yield. DM partitioning to leaves and tubers during the growing season differed among cultivars, but N availability affected partitioning similarly for all cultivars. Jaerla had a high and Huinkul MAG had a low radiation use efficiency between plant emergence and the beginning of tuber formation. Jaerla, Spunta and Mailen INTA reached maximum N content in foliage at approximate to 60 days after emergence and Huinkul MAG 20 days later. Total N content at maturity varied between 120 and 250 kg ha(-1) and was affected by cultivar and N dose. The results will help to improve N fertilization recommendations and management practices as related to each cultivar under the environmental conditions of this region.