The mineralization of urea fertilizer significantly impacts nitrogen movement in the soil. An incubation study was done on a lab scale basis to examine nitrogen dynamics in soil inoculated with plant growth-promoting bacteria (PGPB) supplemented with varying levels of nitrogen fertilizer in the form of urea (0% N, 25% N, 50% N, 75% N, and 100% N). In the present experiment, sandy clay loam soil was used and incubated for four weeks, and the concentrations of NH₄⁺‒N and NO₃–‒N were monitored using the destructive method (Kjeldahl) to determine the mineralization rate of urea. Results showed higher NH₄⁺‒N (11.880 mg/kg mineralized with UPMRB9N50 treatment) and NO₃–‒N (20.060 mg/kg mineralized with UPMRB9N50 treatment) concentrations in the bacteria-treated soil compared to the uninoculated control. Urea-N remains higher (0.0353% and 0.0253% from UPMRB9N50 treatment in the first and second weeks, respectively) in bacteria-treated soil during the first two weeks, then gradually becomes zero towards the end of the observing period. Nitrogen (N) leaching loss was lower in bacterial inoculated soil compared to the control, and the leaching loss of N was greater with the increased N fertilizer rates. Cumulative N leaching loss is higher (29.797 mg/kg) in 100% N-treated soil than in other treatments. The findings observed that the beneficial bacteria could enhance the N mineralization to make the nutrient available for the crop while, at the same time, reducing leaching losses of fertilizer when supplied with a minimum amount of chemical fertilizer, thereby saving the input cost and protecting the environment.

• Abera, G., Wolde-meskel, E., Beyene, S., & Bakken, L. R. (2012). Nitrogen mineralization dynamics under different moisture regimes in tropical soils. International Journal of Soil Science, 7(4), 132-145. https://doi.org/10.3923/ijss.2012.132.145

• Ali-Tan, K. Z., Radziah, O., Halimi, M. S., Abdul Rahim, K. B., Abdullah, M., & Shamsuddin, Z. H. (2017). Growth and yield responses of rice cv. MR219 to rhizobial and plant growth-promoting rhizobacterial inoculations under different fertilizer-n rates. Bangladesh Journal of Botany, 46(1), 481-488.

• Almaz, M. G., Halim, R. A., Martini, M. Y., & Samsuri, A. W. (2017). Integrated application of poultry manure and chemical fertiliser on soil chemical properties and nutrient uptake of maize and soybean. Malaysian Journal of Soil Science, 21(1), 13-28.

• Bundy, L. G. (2001, November 27-December 6). Managing urea-containing fertilizers. [Paper presentation]. Proceedings of the Fertilizer Dealer Meeting, Madison, USA.

• Cardenas, L. M., Hatch, D. J., Scholefield, D., Jhurreea, D., Clark, I. M., Hirsch, P. R., Salazar, F., Rao-Ravella, S., & Alfaro, M. (2013). Potential mineralization and nitrification in volcanic grassland soils in Chile. Soil Science and Plant Nutrition, 59(3), 380-391. https://doi.org/10.1080/00380768.2013.789395

• Chapman, H. D. (1965). Cation‐exchange capacity. In A. G. Norman (Ed.), Methods of Soil Analysis: Part 2 Chemical and Microbiological Properties, 9.2 (Vol. 9). Wiley Online Library. https://doi.org/10.2134/agronmonogr9.2.c6.

• Douglas, L. A., & Bremner, J. M. (1970). Extraction and colorimetric determination of urea in soils. Soil Science Society of America Journal, 34(6), 859-862. https://doi.org/10.2136/sssaj1970.03615995003400060015x

• Gioacchini, P., Nastri, A., Marzadori, C., Giovannini, C., Vittori Antisari, L., & Gessa, C. (2002). Influence of urease and nitrification inhibitors on N losses from soils fertilized with urea. Biology and fertility of soils, 36(2), 129-135. https://doi.org/10.1007/s00374-002-0521-1

• Heffer, P., & Prud’homme, M. (2016). Short-term fertilizer outlook 2016–2017. International Fertilizer Industry Association.

• Jones, J. B. (2001). Laboratory Guide for Conducting Soil Tests and Plant Analysis (Issue BOOK). CRC press.

• Junejo, N., Khanif, M. Y., Hanfi, M. M., Dharejo, K. A., & Wan, Z. W. Y. (2011). Reduced loss of NH3 by coating urea with biodegradable polymers, palm stearin and selected micronutrients. African Journal of Biotechnology, 10(52), 10618-10625. https://doi.org/10.5897/AJB10.394.

• Keeney, D. R., & Nelson., D. W. (1982). Nitrogen-Inorganic forms. In A. L. Page (Ed.), Methods of Soil Analysis, Agronomy Monograph 9, Part 2 (2nd ed., pp. 643-698). ASA, SSSA.

• Kira, O., Shaviv, A., & Dubowski, Y. (2019). Direct tracing of NH3 and N2O emissions associated with urea fertilization approaches, using static incubation cells. Science of The Total Environment, 661, 75-85. https://doi.org/10.1016/j.scitotenv.2019.01.128

• Ladha, J. K., De Bruijn, F. J., & Malik, K. A. (1997). Introduction: Assessing opportunities for nitrogen fixation in rice-a frontier project. Plant and Soil, 194(1), 1-10. https://doi.org/10.1023/A:1004264423436

• LECO. (2018). LECO Corporation, USA. https://www.leco.com/elemental-analysis

• Leghari, S. J., Wahocho, N. A., Laghari, G. M., HafeezLaghari, A., MustafaBhabhan, G., & HussainTalpur, K. (2016). Role of nitrogen for plant growth and development: A review. Advances in Environmental Biology, 10(9), 209-219.

• Lichiheb, N., Myles, L., Personne, E., Heuer, M., Buban, M., Nelson, A. J., Koloutsou-Vakakis, S., Rood, M. J., Joo, E., Miller, J., & Bernacchi, C. (2019). Implementation of the effect of urease inhibitor on ammonia emissions following urea-based fertilizer application at a Zea mays field in central Illinois: A study with SURFATM-NH3 model. Agricultural and Forest Meteorology, 269-270, 78-87. https://doi.org/10.1016/j.agrformet.2019.02.005

• Ma, Z., Yue, Y., Feng, M., Li, Y., Ma, X., Zhao, X., & Wang, S. (2019). Mitigation of ammonia volatilization and nitrate leaching via loss control urea triggered H-bond forces. Scientific Reports, 9(1), Article 15140. https://doi.org/10.1038/s41598-019-51566-2

• Mandal, S., Thangarajan, R., Bolan, N. S., Sarkar, B., Khan, N., Ok, Y. S., & Naidu, R. (2016). Biochar-induced concomitant decrease in ammonia volatilization and increase in nitrogen use efficiency by wheat. Chemosphere, 142, 120-127. https://doi.org/10.1016/j.chemosphere.2015.04.086

• Mariano, E., de Sant Ana Filho, C. R., Bortoletto-Santos, R., Bendassolli, J. A., & Trivelin, P. C. (2019). Ammonia losses following surface application of enhanced-efficiency nitrogen fertilizers and urea. Atmospheric Environment, 203, 242-251. https://doi.org/10.1016/j.atmosenv.2019.02.003

• Motasim, A. M., Samsuri, A. W., Sukor, A. S. A., & Adibah, A. M. (2021). Gaseous nitrogen losses from tropical soils with liquid or granular urea fertilizer application. Sustainability, 13(6), Article 3128. https://doi.org/10.3390/su13063128

• Okalebo, J. R., Gathua, K. W., & Paul, L. W. (2002). Soil bulk density and water holding capasity. In Laboratory Methods of Soil and Plant Analysis: A Working Manual Second Edition (pp.25-260). Sacred Africa.

• Omar, L., Ahmed, O. H., & Majid, N. M. A. (2015). Improving ammonium and nitrate release from urea using clinoptilolite zeolite and compost produced from agricultural wastes. The Scientific World Journal, 2015, Article 574201. https://doi.org/10.1155/2015/574201

• Puga, A. P., Grutzmacher, P., Cerri, C. E. P., Ribeirinho, V. S., & de Andrade, C. A. (2020). Biochar-based nitrogen fertilizers: Greenhouse gas emissions, use efficiency, and maize yield in tropical soils. Science of the Total Environment, 704, Article 135375. https://doi.org/10.1016/j.scitotenv.2019.135375

• Richards, L. A., & Fireman, M. (1943). Pressure-plate apparatus for measuring moisture sorption and transmission by soils. Soil Science, 56(6), 395-404.

• Rochette, P., Angers, D. A., Chantigny, M. H., Gasser, M. O., MacDonald, J. D., Pelster, D. E., & Bertrand, N. (2013). NH3 volatilization, soil concentration and soil pH following subsurface banding of urea at increasing rates. Canadian Journal of Soil Science, 93(2), 261-268. https://doi.org/10.4141/cjss2012-095

• Rochette, P., Angers, D. A., Chantigny, M. H., MacDonald, J. D., Gasser, M. O., & Bertrand, N. (2009). Reducing ammonia volatilization in a no-till soil by incorporating urea and pig slurry in shallow bands. Nutrient Cycling in Agroecosystems, 84(1), 71-80. https://doi.org/10.1007/s10705-008-9227-6

• Shan, L., He, Y., Chen, J., Huang, Q., & Wang, H. (2015). Ammonia volatilization from a Chinese cabbage field under different nitrogen treatments in the Taihu Lake Basin, China. Journal of Environmental Sciences, 38, 14-23. https://doi.org/10.1016/j.jes.2015.04.028

• Sharifuddin, H. A. H., Fauziah, I., & Zaharah, A. R. (1990). Technique of soil testing and plant analysis and their utilization for crop production in Malaysia. Communications in Soil Science and Plant Analysis, 21(13-16), 1959-1978. https://doi.org/10.1080/00103629009368350

• Teh, C. B. S., & Talib, J. (2006). Soil and Plant Analyses Vol. I Soil Physics Analyses. Department of Land Management, Faculty of Agriculture, Universiti Putra Malaysia.

• Wang, X., Xu, S., Wu, S., Feng, S., Bai, Z., Zhuang, G., & Zhuang, X. (2018). Effect of Trichoderma viride biofertilizer on ammonia volatilization from an alkaline soil in Northern China. Journal of Environmental Sciences, 66, 199-207. https://doi.org/10.1016/j.jes.2017.05.016

• Zadeh, F. S. (2010). Sorptiob-desorption, degradation and leaching of napramide in selected malaysian soils [Unpublish doctoral thesis]. University Putra Malaysia, Malaysia.

• Zhao, M., Tian, Y., Ma, Y., Zhang, M., Yao, Y., Xiong, Z., Yin, B., & Zhu, Z. (2015). Mitigating gaseous nitrogen emissions intensity from a Chinese rice cropping system through an improved management practice aimed to close the yield gap. Agriculture, Ecosystems & Environment, 203, 36-45. https://doi.org/10.1016/j.agee.2015.01.014

• Zuki, M. M. M., Jaafar, N. M., Sakimin, S. Z., & Yusop, M. K. (2020). N-(n-Butyl) thiophosphoric triamide (NBPT)-coated urea (NCU) improved maize growth and nitrogen use efficiency (NUE) in highly weathered tropical soil. Sustainability, 12(21), Article 8780. https://doi.org/10.3390/su12218780