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Densification of biochar can reduce transportation and handling costs, as well as significantly decrease loss of biochar during soil application. Although the nutrient-rich biochar tablets may be a potential cost-effective slow-release fertilizer in soil, there is a lack of information on characterization of mixtures of rubber tree twigs and rice residues tablets with embedded NPK fertilizer. Objective of this work was to determine the physical and chemical properties of biochar tablets with and without embedded fertilizer. Biochar tablets were produced by blending of charred rice husk, rice straw, rubber tree twigs, and starch and followed by tableting. Their production with embedded fertilizer was similar to production process of tablets without it, except adding the NPK fertilizer to blending phase prior to tableting. Fourier-transform infrared spectra analysis indicates was utilized for determination of presence of ammonium and phosphorus substances in the biochar tablets with embedded fertilizer (BFs). The NPK fertilizer significantly increased tablet density and total contents of nitrogen, phosphorus, potassium, calcium and magnesium. The presence of higher amount of nutrients in BFs suggests that it could release nutrients for plant use.

Currently, there is an abundance of interest in the methods to reduce ammonia (NH3) volatilization and nitrous oxide (N2O) emissions from cultivated soils. Nitrogen use efficiency (NUE) of applied urea is decreased due to gaseous loss, which also lowers soil N (Nitrogen) content. The purpose of this study was to investigate the potential of microbial-based inoculants to decrease NH3 loss and N2O emissions under controlled conditions. Bacillus subtilis ;(UPMB10), and Bacillus tequilensis ;(UPMRB9) in combination with five different nitrogen (N) fertilizer levels 0%, 25%, 50%, 75%, and 100% were used in this study. Results showed that NH3 cumulative volatilization loss was greater in uninoculated soil treated with a full dose of fertilizer-N (507.27 mg/kg) compared with bacterial-inoculated soil (491.20 mg/kg and 500.71 mg/kg for UPMRB9 and UPMB10, respectively). Emission of N2O increased to a greater level (15.11 mg/kg for B0N100) in uninoculated soil compared to inoculated soil (14.65 mg/kg for UPMRB9N100 and 14.93 mg/kg for UPMB10N100-treated soil) and emission of N2O increases as N application increases. Initially, the emission of N2O was greater which decreased from the sixth day until it became zero. In B0N100-treated soil, emissions of N2O increased and after 30 days of incubation, the inoculated soil had a greater N concentration than the uninoculated soil. The total N loss from applied urea was higher in uninoculated soil than in inoculated soil. According to the findings, microbial inoculants have the potential to reduce the loss of N through NH3 volatilization and N2O emissions. [ABSTRACT FROM AUTHOR]

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 bacteriatreated 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. [ABSTRACT FROM AUTHOR]

Densification of ashy biochar into tablet can enhance the handling and conveyance efficiencies of biochar. It was hypothesized that fertilizer-embedded biochar tablets can slowly release embedded nutrients in synchrony with optimum nutrient uptake by crops. The objectives of this research were to determine the effects of biochar tablets with and without embedded fertilizer on soil chemical properties and nutrient use efficiency of Zea mays (sweet corn). The biochar tablet (BT) was produced by blending a biochar mixture with starch followed by densification using a single punch tablet press whereas the fertilizer embedded biochar tablet (BF) was prepared using the same procedure except that NPK fertilizer was added during blending. A pot experiment with five fertilization treatments including control was carried out in an open field located in Perlis, Malaysia. Co-application of biochar and fertilizer increased soil total carbon, nitrogen, but it reduced soil electrical conductivity (EC). Additionally, the BF significantly increased leaf chlorophyll content, dry root weight, and total plant nutrient use efficiency of sweet corn. The findings suggest that BF can serve as a slow release fertilizer to improve crop nutrient use efficiency. Therefore, embedding fertilizer in biochar tablets is recommended for sweet corn production following a long term field study to confirm the findings of this pot study. [ABSTRACT FROM AUTHOR]