INVESTIGATING THE EFFECT OF BIOCHAR AND COMPOST AMENDMENTS ON Na+/K+ RATIO IN SOIL AND RICE YIELD ON SALINE-AFFECTED SOIL

Abstract

Saline intrusion leads to high Na⁺ content, causing nutrient imbalance, hindering nutrient absorption for crop, thus reducing crop yields. The objective of this study was to evaluate the effect of biochar and compost amendments on exchangeable and soluble forms of K⁺ and Na⁺ in soil and rice yield. A field experiment was carried out in U Minh Thuong district, Kien Giang province, over six consecutive rice crops during two years. Four treatments with four replications were designed in a completely randomized block. The treatments included: (1) three continuous rice crops per year (LLL), (2) two rice crops per year (LL), (3) LL combined with compost at 3 tons/ha/crop (LL + PHC) and (4) LL combined rice husk biochar at 10 tons/ha/crop (LL + TSH). The study results showed that two rice crops combined with biochar amendment at 10 tons/ha significantly increased soluble and exchangeable K⁺ and reduced the Na⁺/K⁺ ratio in soil across each cropping season. The highest rice yield was observed in the biochar treatment after six consecutive crops, showing a significant difference compared to treatments with only inorganic fertilizer application. However, compost amendment did not significantly affect exchangeable and soluble of K⁺, Na⁺/K⁺ ratio in the soil and rice yield. Notably, the significant negative correlation between the Na⁺/K⁺ ratio and rice yield indicates that reducing Na⁺ and increasing K⁺ in soil are important factors for enhancing rice yield. Therefore, biochar can be considered as a potential amendment for improving saline-affected soil and rice yield in the Mekong delta.