Objective: The purpose of this study was to the influence of fertilizers and the use rate of fertilizer for soil improvement on the yields, and starch content of cassava. Method: The experiment design was in RCBD with 9 treatments, which were as follows; T1 (Control), T2 (ORG 50 kilograms/rai.), T3 (ORG 100 kilograms/rai.), T4 (HO-1 50 kilograms/rai.), T5 (HO-1 100 kilograms/rai.), T6 (HO-2 50 kilograms/rai.), T7 (HO-2 100 kilograms/rai.), T8 (CHEM 50 kilograms/rai.), and T9 (CHEM 100 kilograms/rai.) The experiment plots were located at Pasao, Muang District, Uttaradit Province, from June 2017 – June 2018. by using the DMRT method at 95% confidence. Results and Conclusions: The result showed that yield components, the use of HO-2 fertilizer 100 kilograms/rai. The formula of yield quality for cassava. It has the mean number of tubers per plant 17.00 tuber/ plant, number of root length 47.75 cm., and the cassava tuber circumference 25.25 cm. significantly different at 95%. While the components of average weight/tuber 0.67 kilograms/tuber and yield weight/tree 10.55 kilograms/plant were the highest among other treatments. But there was no statistical difference at 95%. However, when considering the highest average yield per rai, It was found that using HO-2 fertilizer 100 kg/rai gave a higher yield than other treatments (5,110 kilograms/rai). The rate of 100 kilograms/rai resulted in a higher percentage of cassava starch content than other methods (30.50%), which was statistically significantly different at 95%, better than using chemical fertilizers, organic granular fertilizers, and without fertilizers (Control). In terms of cost and profit, It was found that using 100 kg/rai of HO-2 fertilizer resulted in the highest profit from product sales per rai of 10,458 baht/rai, which was higher than using chemical fertilizers and organic granular fertilizer. Moreover, HO fertilizer was a choice to manage soil and fertilizer that affects the cassava product quality in Uttaradit Province. Research implications: The hormone mixed formula (HO) fertilizer 100 kilograms/rai had certain impact on the improvement on chemical properties and the soil physical appearance than not putting the fertilizer, that the HO-2 100 kilograms per rai was suitable for increasing the productivity and percentage of starch content of cassava. Originality/value: This study evaluates fertilizer types and application rates on cassava yield and starch content in Uttaradit Province, Thailand. Using a randomized complete block design, it provides insights into soil fertility and productivity improvement. The study also assesses profitability, offering practical insights for farmers.