The carbon-to-nitrogen ratio of organic matter refers to the proportion of carbon to nitrogen present and is the basis for determining the quality of ameliorant. Amelioration technology is a solution for increasing soil and plant productivity in an agricultural area using local resources (biomass and waste). This study aims to determine the estimated C/N ratio of the formulation of ameliorant. This research used a completely randomised design with three replications of fifteen treatments by four formulation ameliorants. The primary local resources are biochar from bamboo biomass, green fertiliser from Tithonia diversifolia, chicken manure from livestock waste, and compost from agricultural waste. The estimated C/N ratio for the formulation of ameliorant from local resources in the Horticultural Production Center of Banuhampu Agam is 2.89 (TGF+CM) to 17.75 [biochar bamboo (BB)]. It explains that organic substrates sourced experience rapid mineralisation and release N so that N is available for plant absorption. The correlation of C/N on the characteristics of ameliorant formulations shows that it has a significant effect on C [r = 0.720** or C = 0.1689 (C/N) + 3.2857; R2 = 0.5185] and N [r = -0.763** or N = - 0.051(C/N) + 1.1629; R2 = 0.5815]. The results of the formulation of ameliorant from local resources show that the Organic C of 2.53% (BB+TGF) until 7.59% [biochar bamboo (BB)] have a positive correlation and Total N of 0.29% [Thitonia green fertiliser (TGF)] until 1.30% (TGF+CM+CA) have a negative correlation to C/N ratio. Adding BB can increase the C/N ratio of the ameliorant formulation due to its carbon sequestration and using TGF+CM for the lower C/N ratio application needed.