Cassava (Manihot esculenta Crantz) currently is grown in more than tropical and subtropical 100 countries including Vietnam. To cater to the strategy of Cassava sustainable development in Bao Yen district - Lao Cai province, the research and development of cassava cultivation technique containing fertilizing suitable with ecological zones is an effectively way. The results showed that when fertilizing to the variety KM94 increased from 10 tons of manure + 40 kg P2O5 + 60kg K2O/ha (treatment 2) to 10 tons of manure + 80kg K2O/ha 80kg N + 60kg P2O5 (treatment 3), the fresh tuber yield was 6.9 tonnes / ha, the biological productivity was 9.5 tons/ha respectively
when fertilizer continues to increase up to 10 tons of manure + 120kg N + 120kg K2O/ha 100kg P2O5 (treatment 5), the fresh tuber yield was 4.4 tons/ha, the biological productivity was 11.4 tons/ha. The fertilization guideline that was suitable for cassava KM94 in Bao Yen district, Lao Cai province was 10 tons of manure + 80kg N + 60kg P2O5 + 80kg K2O/ha. This was the fertilizer treatment that had the highest fresh tuber yield (33.8 tons/ha) and the highest economic efficiency (35.39 millions VND/ha).