Resumen
The application of urea fertilizer in agriculture industry has contributed to the advancement of crop production every year. Nevertheless, its low efficiency has led to high nitrogen losses in the form of Ammonia (NH3) and Nitrous Oxide (N2O) gases. Allicin, an organosulfur compound from garlic (Allium savatium L.) is identified as the most potential candidate for urease bio-inhibitor to delay the urease enzyme activity in hydrolysis process. However since it is highly unstable, it will decompose into other stable compounds mostly consist of diallyl disulfide (DADS). This research mainly aims to evaluate the efficacy of Allicin and DADS in soil urease inhibition. The inhibition study of Allicin and DADS have been conducted by applying both compounds on urea at the soil and the loss of applied urea was quantified by using diacetylmonoxime (DAM) colorimetric method. Next, the stability study is done via High Performance Liquid Chromatography (HPLC) at different soil conditions; pH (3-11), temperature (30-80°C) and moisture content (10-50%). In overall, the result justified that DADS managed to achieve 20% higher inhibitory action of urease enzyme compare to Allicin. In addition, DADS also exhibited higher stability despite of the variation of soil condition compare to Allicin and the optimum soil condition for higher inhibitory action is identified at 30% moisture, 30°C and pH 7. Since the condition satisfied the typical soil condition in Malaysia, hence the application of urease bio-inhibitor is highly applicable to improve the utilization of nitrogen in soil.