<p>Rice production in Cambodia faces challenges due to water scarcity and improper fertilizer use, which raise environmental concerns. Integrating biochar and water-saving irrigation methods offers a promising solution for farmers. This study evaluated how biochar and chemical fertilizers affect rice yield, quality, and nutrient loss under different soil types and irrigation methods. A column experiment was conducted using clay (S1) and sandy loam (S2) soils, with two irrigation methods: alternate wetting and drying (AWD) and continuous flooding (CF). The treatments included a control (T0), chemical fertilizer only (T1), chemical fertilizer supplemented with 4 tons per hectare (t ha⁻¹) of biochar (T2), and chemical fertilizer supplemented with 6 t ha⁻¹ of biochar (T3). Across both soil types and irrigation methods, T3 resulted in the highest dry grain yield and protein content compared to T1. This biochar at 6 t ha⁻¹ was effective in both clay and sandy loam soils, though its efficiency varied slightly; for instance, under AWD irrigation, rice yield increased by approximately 35% in sandy loam and 40% in clay soil. Biochar application at 6 t ha⁻¹ significantly reduced the leaching of NO₃⁻, NH₄⁺, and PO₄³⁻ compared to other treatments. Although there were no significant differences in amylose content among the treatments, biochar application positively influenced plant biomass and chlorophyll content. These results show that increasing the biochar rate from 4 to 6 t ha⁻¹ further enhances rice yield and protein content without affecting amylose content, while both rates reduce nutrient leaching and contribute to more sustainable farming practices.</p>