Yam is a worldwide consumed vegetable and is considered an alternative crop that is in expansion. However, the average yield of this crop is low, probably due to the low availability of nutrients in the soil of cultivated areas. The present study evaluated the production of yam, Da Costa, cv., as a result of nitrogen fertilization. An experiment was carried out between March and December/2005 at Universidade Federal da Paraíba, in Areia, Brazil. A randomized block design was used, with five levels (0; 50; 100; 150 and 200 kg ha-1), supplied in covering fertilization, with four replications. The estimated length of rhizophors was 32 cm reached using 70 kg ha-1 of N. The average mean diameter of 7.0 cm, was not affected by N levels. The mean weight of rhizophors increased up to 1.5 kg, when an estimated N level of 120 kg ha-1 was applied. The maximum yield of commercial rhizophors was 19.2 t ha-1, from an estimated N level of 120 kg ha-1, while the economical yield of commercial rhizophors was 13.9 t ha-1 obtained when N level of 118 kg-1 were used. The N contents in leaves of yam increased linearly with levels of N fertilization.
Dioscorea cayennensis Lam.; mineral fertilization; yield
