Effect of Natural Based Bio-inhibitors and N (n-butyl) Thiophosphoric Triamide (NBPT) for Slow Release Fertilizer (SRF) Application

The application of N (n-butyl) Thiophosphoric Triamide (NBPT) as urease inhibitor with urea fertiliser have shown presence of chlorosis and necrosis on plant leaves that decreases the amount of chlorophyll pigments essential for photosynthesis reaction. Three types of vegetables, Spinach (Spinacia oleracea), mustard green (Brassica juncea) and water spinach (Ipomoea aquatica) are cultivated in soil lasting 4 weeks and irrigated with deionized water daily and fertilized with urea, NBPT and Thiosulfinates (TS) at different concentrations (0%, 0.012%, 0.062%, and 0.125%). The physical changes and the chlorophyll concentration were analysed using Trichromatic method. Besides that, inhibition studies to show the potential of TS in garlic extract as a bio based inhibitor is conducted to compare the inhibition performance with chemical based inhibitor, NBPT. The plants treated with 0.125% of NBPT had the least chlorophyll concentration compared to control plants treated with only urea. This might be due to ammonium toxicity experienced by the plants which then led to the decrease in chlorophyll pigments. In addition, both NBPT and TS exhibit inhibition abilities but showed different trends. Inhibition by TS began earlier but lasted only for 20 minutes while NBPT showed a much longer period but began after 60 minutes of application. As a conclusion, the chlorophyll results showed that NBPT did effect the plant growth which is proportional to the concentration of NBPT applied. Hence, bio based urease inhibitor like TS should be considered as one of the alternative to replace chemical based inhibitors for a more sustainable future in the agriculture sector.