Results of Testing on Application Rate of the Specialized Organic Blended Fertilizer on Flue Cured Tobacco in the North Mountains of Vietnam

Province Cao Bang is one of the dominant flue-cured tobacco (FCT) producing areas in the northern mountainous region of Vietnam. Here, a specialized organic mineral mixed fertilizer (OM-NPK), with analysis of N-P2O5-K2O-organic matter-humic being 5-4-9.5-10-0.4%, was tested on the application rate of this grade to FCT in the Spring crop of 2021 with 03 rates as follows: 1 ton/ha, 1.1 ton/ha and 1.2 ton/ha, compared with the control of specialized inorganic mixed fertilizer being named VTL: MN (analysis of N-P2O5-K2O is 5.8-7.5-13.5%) and the background treatment (no fertilizer). The experiment, including 05 treatment, was arranged in a randomized complete block design (RCBD) with 03 replications on the main tobacco-growing soil in the Cao Bang, which is heavy soil. The results of this study showed that all 03 treatments on the application rate of OM-NPK fertilizer met the requirements of the test based on the fertilizer use efficiency (beyond the control by 10%), in which the treatment with the application rate of 1-ton OM-NPK/ha gave the best performance (reliability 0.05). At the same time, the density of micro-organisms dissolving insoluble phosphorus in the soil was higher in treatments of the OM-NPK application than the control.