Cassava is considered as traditional crop in Vietnam, and the farmers have been contributing their efforts to improve cultivation technologies, however, it seems very little, then cassava yield is still low. Basically, main reason is lack of soil measures and management, and low investment due to lack of capital. Therefore, accompanying with new varietal introduction, it is needed to intensification plays an important role in soil fertile conservation, yield increasing and root quality. Within the framework of Participatory Research for Development in the Upland Project (PRDU), a project managed by the International Center for Tropical Agriculture (CIAT), a trial on Cassava fertilization based on KM94 was carried out at Hung Duc commune (Ham Yen district, Tuyen Quang province) aimed at to study the effectuation of fertilization combinations to the development and yield of KM94, a common variety in Cassava production at the research sites. The trial consists of 4 treatments, 3 replicates. Treatment 1: 7 tons of cattle manures + 360 kg NPK (5-10-3)/ha
Treatment 2: 7 tons of cattle manures + 40 kg N + 40 kg P2O5 + 80 kg K2O/ha
Treatment 3: 7 tons of cattle manures + 60 kg N + 40 kg P2O5 + 100 kg K2O/ha
Treatment 1: 7 tons of cattle manures + 80 kg N + 60 kg P2O5 + 120 kg K2O/ha
Of which, treatment 1: 7 tons of cattle manures + 360 Kg NPK (5-10-3) as farmer's practice for the control of the trial. The trial result showed that: among 4 treatments, the treatment 4: 7 tons of cattle manures + 80 kg N + 60 kg P2O5 + 120 kg K2O per ha has fresh root yield (44.50 tons/ha), higher than the control about 11.1 tons/ha. This treatment also has highest net income (12.18 million VND per ha), higher the control, 3.26 million VND per ha only.