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Increasing the efficiency of maize production in Vietnam is a prerequisite for increasing the quantity of maize for animal feed. With a view to reducing nitrogen-phosphorus-potassium (NPK) doses for maize production, a two-factor experiment using complex micronano particles across three NPK fertiliser doses and three densities on maize hybrid PAC999 was conducted following a randomized complete block design with plot size of 21.84 m2, in Binh Dinh province of Vietnam from May to September 2017. Three NPK fertiliser doses (kg/ha) constitute the first factor, as P1: 156 N - 86 P2O5 - 84 K2O (100% normal dose); P2: 140 N - 77 P2O5 - 76 K2O (90%); and P3: 125 N - 69 P2O5 - 67 K2O (80%). Three densities constitute the second factor, as M1: 71,429 plants/ha (100% normal density); M2: 64,935 plants/ha (90%), and M3: 57,143 plants/ha (80%). Nine combinations of M and P were developed into nine treatments; the control involved spraying with water rather than nano foliar fertiliser. Nano particles were applied as a foliar fertiliser solution at 20 days after sowing with 300 litres/ha, 30 days after sowing with 500 litres/ha, and 40 days after sowing with 700 litres/ha. The results show that 80% and 90% of normal NPK doses combined with 90% and 80% normal density produced a grain yield of 6.52 and 6.63 tons per ha, respectively, which is 14-16% higher than that of the control (5.71 tons/ha). The results of the experiment were demonstrated on large plots of 500 m2 each in summer/autumn 2018 in Binh Dinh and Hau Giang provinces, spring/summer 2018 in Long An, and winter/spring 2017-2018 in Dong Nai province. Over an area of 500 m2, 75% of farmers' NPK doses and the micronano solution were applied; the control involved applying 100% NPK doses. The results of the demonstration showed that the grain yield of maize (tons/ha) with the nano fertiliser solution (9.44 in Binh Dinh, 9.2 in Dong Nai, 9.52 in Long An, and 8.7 in Hau Giang) was 0.95, 0.28, 0.68, and 0.3 tons higher than that of the control (8.49, 8.92, 8.84, and 8.4 tons/ha, respectively).