Studies with the objective of increasing yield and quality of sweet potato roots, could be an important tool to improve the socio economic condition in the northeastern area of Brazil, due to the importance of this vegetable in that area. The present work was done to evaluate the effect of urea levels on yield and quality of sweet potato cultivar Rainha Branca. The experiment was conduced from July to November/2003, in Paraíba State, Brazil. The experimental design was of randomized blocks with five treatments (0; 115; 230; 345 and 460 kg ha-1 of urea), in cover fertilization at 30 and 60 days after planting date, in four replications. Plots with 28 plants, spaced 0,80 x 0,30 m apart were used. Commercial root yield of 18.8 t ha-1 was obtained when 339 kg ha-1of urea were employed, a much better result compared to the national average of 8.8 t ha-1of commercial roots The glucose level (reducing sugars) on the sweet potato roots, increased with the increase of the urea levels, up to 187 kg ha-1of urea with a maximum of 8.7% of glucose. Starch level was reduced with increasing urea levels, with minimum percent of 57% at the level of 460 kg ha-1. However, the starch minimum level was within the range defined for this species.
Ipomoea batatas; mineral nutrition; yield; glucose; starch
