Yam quality affected by nitrogen fertilization and harvest timeYam is a highly nutritive horticultural crop of great importance in the Northeastern region of Brazil. This study was developed in Paraíba State, Brazil, from March to December/2002, to quantify the dry matter, starch and yam ash content of rhizophors of the Da Costa cultivar, grown in Ustipsamment soil. Treatments were five N levels (0; 50; 100; 150 and 200 kg ha-1) and two harvest times (seven and nine months after planting date). A factorial scheme 5 x 2 in randomized blocks with four replications was used. Dry matter content increased from 33.2% to 34.1% comparing harvest dates of seven and nine months after planting, not being influenced significantly by N levels. Starch content increased from 21.5% to 25.3%, at nine months. The starch content at nine months increased with increasing N levels, reaching the maximum value of 30% at 55 kg ha-1 of N. The ash content was affected by N levels increasing until 65 kg ha-1 of N and reaching the maximum value of 0.8%. At nine months, an average value of 0.8% was obtained, without significant effects of N levels.
Dioscorea cayennensis Lam.; harvest time; mineral fertilization; chemical composition
