Synthesis and Characterization of Slow-Release Fertilizer Hydrogel Based on Hydroxy Propyl Methyl Cellulose, Polyvinyl Alcohol, Glycerol and Blended Paper

In this study, biodegradable slow-release fertilizer (SRF) hydrogels were synthesized from hydroxyl propyl methyl cellulose (HPMC), polyvinyl alcohol (PVA), glycerol and urea (SRF1) and HPMC, PVA, glycerol, urea and blended paper (SRF2). The fertilizer hydrogels were characterized by SEM, XRD and FTIR. The swelling capacity of the hydrogels in both distilled and tap water as well as their water retention capacity in sandy soil were evaluated. The hydrogels had good swelling capacity with maximum swelling ratio of 17.2 g/g and 15.6 g/g for SRF1 and SRF2 in distilled, and 14.4 g/g and 15.2 g/g in tap water, respectively. The water retention capacity of the hydrogels in sandy soil exhibited higher water retention when compared with soil without the (SRFs). The soil with the hydrogels was found to have higher water retention than the soil without the hydrogels. The slow-release profile of the hydrogels was also evaluated. The result suggested that the prepared fertilizer hydrogels has a good controlled release capacity. The blended paper component in SRF2 was observed to aid effective release of urea, with about 87.01% release in soil at 44 days compared to the pure urea which was about 97% release within 4 days. The addition of blended paper as a second layer matrix was found to help improve the release properties of the fertilizer. The swelling kinetic of the hydrogel followed Schott’s second order model. The release kinetics of urea in water was best described by Kormeye Peppas, suggesting urea release to be by diffusion via the pores and channels of the SRF, which can be controlled by changing the swelling of the SRF. However, the release mechanism in soil is best described by first order kinetic model, suggesting that the release rate in soil is depended on concentration and probably on diffusion rate via the pores and channels of the SRF.

Nutrient Release and Ammonia Volatilization from Biochar-Blended Fertilizer with and without Densification

Blending fertilizer with biochar followed by densification to make it into a tablet can enhance the adsorption of fertilizer on the biochar surface and reduce the nutrient loss during handling. However, the nutrient release and ammonia volatilization from biochar-blended fertilizer with and without densification are not well understood. The objectives of this study were to determine the nutrient release and ammonia volatilization from an acid soil applied with biochar-blended NPK fertilizer with and without densification. The nutrient release of biochar-blended NPK was determined using water incubation for 30 days, whereas daily loss of ammonia was measured using a closed dynamic air flow system for 10 days. The densified biochar-blended NPK caused stronger physical binding of the nutrients within the tablet in addition to stronger chemical bondings between the nutrients with the biochar’s functional groups. As a result, nutrient release in the water incubation from the biochar-blended NPK fertilizer tablet was slower. However, blending the biochar with the NPK fertilizer increased soil ammonia volatilization relative to the NPK fertilizer alone. This demonstrates that the biochar-blended fertilizer tablet has the potential to serve as a slow release fertilizer for crop cultivation.

The Potential of Biogas Slurry and Palm Oil Mill Effluent Slurry as Slow-Release Fertilizer Pellet Through Densification

Organic fertilizer can yield higher production compared to regular fertilizer if properly applied. Thus, it can be a solution to improve nutrient content of soil. The biggest source of bio slurry in plantation is from Palm Oil Mill Effluent (POME) and cow dung biogas. This research aimed to analyze the residue’s potential from the result of biogas processing and bio slurry from POME as slow-release fertilizer pellet. Bio slurry was processed into pellet through densification process using pellet mill. The research was arranged in a Randomized Block Design method with five slurry compositions as treatments, including 70:30, 60:40, 50:50, 40:60, and 30:70 (ratio of biogas slurry and POME slurry), each consisted of three replications. According to the data obtained, fertilizer pellets had characteristics of 25 – 29 mm of length, 5.23 – 5.85 mm of diameter, 0.44 – 0.53 g/cm3 of density, 54.78% - 81.96% of durability, and 7.81% - 8.57% of moisture content. Based on density and durability aspects, 30:70 composition was the higher. Macronutrient content of the five compositions were 1.88% - 2.72%, in which on day 22, N, P, and K release was 0.36 – 1.01%, 73.51 – 97.48%, and 3.19 – 7.85%, respectively. Meanwhile, on day 17, the nutrition solution conductivity of all compositions had already reached 0.80 – 1 mS/cm.