This study was carried out to evaluate the effect of nitrogen source on dry mass accumulation and absorption, distribution and also use of nitrogen by cassava plants. Cigana Preta cultivar plants were grown in nutrient solutions set up in 11.0 L containers. Nitrogen concentration in solutions was 12 mol m-3. Treatments included five combinations of NO3-:NH4+ , that is, 12:0, 9:3, 6:6, 3:9 and 0:12 mol m-3. Aftert 90 days the dry mass was determined. The lowest total dry mass values were obtained for plants grown with just nitrate or ammonium as nitrogen source. In this sence, ammonium affected growth more than the nitric source. The concentration of free NH4+ was higher for absorption in roots, followed by leaves and storage roots. The efficiency of nitrogen absorption was higher for plants cultivated under highest proportions of NH4+. The results showed that cassava plants grow more when growth solution contains a mixture of NO3- and NH4+, especially at the proportions of 9:3 and 6:6 mol m-3.
dry matter; leaf area; storage root; root; nitrogen use efficiency