| dc.description.abstract | Nitrogen is one of plant nutrients which are most important for plant growth. However, nitrogen is easy leaching from the soil as nitrate, volatilizing as ammonia gas, or change to other forms which are difficult to be absorbed by crops. To increase the nitrogen efficiency, the fertilizer is made as slow release form. It is well known that zeolite is mineral having high cation exchange capacity (CEC) and capability to adsorb nitrogen as amonium ion. On the other hand, humic acid extracted from organic matter has capability to stimulate plant growth. The objectives of this research were to study the role of zeolite and humic acid as slow release agent of nitrogen fertilizer. The experiment was carried out by incubation method during 14 weeks. The ratio of urea and zeolite was 70%:30% then added by humic acid of 0, 2, 3, 4, and 5% resulting UZA-1, UZA-2, UZA-3,-UZA-4, AND UZA-5. The fertilizers were given equivalent to 50 mg/kg and put them into plastic bottle containing equivalent to lOOg oven-dry soil. The fertilizer and soil then mixed homogenously under field capacity soil moisture. The contents of ammonium-N and nitrate-N were analyzed at 1, 2, 3, 4, 6, 8, 10, 14 week of incubation period. The results indicated that ammonium-N had been detected at the first week incubation and decrease until near zero at the third week incubation. Meanwhile, the nitrate-N showed a continuous increase during the incubation period. The slowest nitrogen release showed by UZA-5. In green house experiment using rice plant showed that UZA-3 gave the best performance of rice growth. | en |
