Effects of plant density and nitrogen fertiliser quantity on the growth, development and yield of pigmented rice Cham Dao in Muong La district, Son La province

The Cham Dao pigmented rice cultivar, traditionally grown in Muong La district, Son La province, has been cultivated in both upland and wet fields.As a matter of fact, the area under Cham Dao cultivation decreased over time because of varietal degeneration.Moreover, traditional cultivating techniques of the local people were no longer suitable, with little fertiliser applied after many years of upland farming, resulting in low productivity (about 1.5 t ha -1 ).The implementation of a study on improving technologies applied to the locally pigmented rice "Cham Dao" in 2021 and 2022, within this context, has partly contributed to increasing the yield and income of the farmers.The field trials consisted of 2 factors: nitrogen (N) fertiliser at 3 dosages (30, 50, and 70 kg N ha -1 ) and 3 planting densities (20, 16, and 13 hills m -2 ), which were arranged in main plot and sub-plot style (split plot design).Study results show that, the application of 1 ton of microbial organic fertiliser +70 kg N+60 kg P2O5+60 kg K2O for wet rice at a planting density of 13 hills m -2 gave the highest net yield (36.6 quintals ha-1 in 2021 and 38.3 quintals ha -1 in 2022) compared to 15.7 quintals ha -1 in 2021 and 14.8 quintals ha -1 in 2022 in upland fields.