Abstract :
[en] Rice serves as the cornerstone of Cambodia's agricultural economy and food security; however, its cultivation faces persistent challenges related to soil fertility, nutrient management, and fertilizer leaching. This dissertation investigates the potential of rice husk-derived biochar as a sustainable soil amendment aimed at mitigating nutrient loss, enhancing rice yield, and improving grain quality. With Cambodia's abundant supply of rice husks and their high silica content, biochar emerges as a locally viable solution for boosting soil health. The study, conducted over two years at the Cambodian Agricultural Research and Development Institute, comprised greenhouse column experiments that explored the interactions between biochar and chemical fertilizers across various soil textures and irrigation methods.
First-year experiment: The focus was on a single soil type to evaluate the combined effects of rice husk biochar and chemical fertilizers on nutrient leaching and rice performance. Results showed that the application of biochar at 4 t ha⁻¹ together with chemical fertilizers (CHEM + BIO4) significantly reduced ammonium (NH₄⁺) and nitrate (NO₃⁻) leaching compared to fertilizers alone, particularly from the plow sole. This reduction was attributed to the sorption capacity of biochar. Furthermore, CHEM + BIO4 improved rice yield, biomass, tiller number, panicle length, grains per panicle, and grain weight per panicle. However, biochar did not significantly reduce phosphate (PO₄³⁻) losses, suggesting its effectiveness is greater for nitrogen management.
Second-year experiment: The scope expanded to include clay (S1) and sandy loam (S2) soils under two irrigation regimes, continuous flooding (CF) and alternate wetting and drying (AWD). Treatments included chemical fertilizers alone (T1) and in combination with biochar at 4 t ha⁻¹ (T2) and 6 t ha⁻¹ (T3). Across both soil types and irrigation methods, the T3 treatment (CHEM + BIO6) achieved the highest dry grain yields and protein content while significantly lowering losses of NO₃⁻, NH₄⁺, and PO₄³⁻. Although amylose content did not differ among treatments, biochar application increased plant biomass and chlorophyll content, underscoring its positive effect on crop performance.
Overall, the two-year findings highlight that rice husk biochar, particularly at rates of 4-6 t ha⁻¹, can enhance nutrient retention, increase rice yield and protein content, and support more sustainable water and nutrient management in Cambodian rice systems. This research contributes to the growing body of evidence on biochar’s role in climate-smart agriculture. Moreover, while both studies demonstrate clear short-term advantages, long-term field trials remain critical to evaluate sustained impacts on soil health, yield stability, and economic viability.
