Journal of Experimental Agriculture International

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.