Abstract:As a source of organic fertilizer, livestock and poultry waste has the potential to replace chemical fertilizers in improving rice yield and nitrogen use efficiency. In this study, a pot experiment was conducted using paddy soils from Hunan Province developed from different parent materials, to investigate the effects of various proportions of cow manure organic fertilizer (30%, 50%, 60%, 75%, and 100%) combined with chemical fertilizers on rice yield and nitrogen absorption under equal nitrogen conditions. The results showed that rice yield was highest when the cow manure organic fertilizer substitution ratio was 60%, 75%, and 30% in paddy soils developed from sandstone weathering, river and lake sediments, and shale weathering, respectively, with significant differences. The nitrogen harvest index was highest with the 75% cow manure + chemical fertilizer treatment in paddy soils developed from granite weathering and sandstone weathering. The highest nitrogen harvest index in limestone weathering paddy soils was observed with 60% cow manure + chemical fertilizer, while in Quaternary red clay paddy soils, the highest nitrogen harvest index was observed with 50% or 100% cow manure + chemical fertilizer. The highest nitrogen absorption efficiency was achieved with the 30% cow manure + chemical fertilizer treatment in paddy soils developed from shale weathering. The highest nitrogen use efficiency was found in paddy soils developed from granite weathering and river lake sediment with the 75% cow manure + chemical fertilizer treatment. The nitrogen partial productivity was highest at the 60%, 75%, and 30% cow manure + chemical fertilizer ratios for paddy soils developed from sandstone weathering, river and lake sediments, and shale weathering, respectively, with significant differences. The study shows that the effects of different proportions of cow manure organic fertilizer on rice yield and nitrogen uptake and utilization vary across paddy soils developed from typical soil parent materials in Hunan Province. Therefore, the suitable organic replacement ratio for nitrogen fertilizer in paddy fields should consider the differences in soil parent materials.