Volume 11, Number 1 (October 2023):5037-5046, doi:10.15243/jdmlm.2023.111.5037 ISSN: 2339-076X (p); 2502-2458 (e), www.jdmlm.ub.ac.id
Open Access 5037 Research Article
Synthesis of slow-release fertilizer with coconut shell biochar and activated natural zeolite for red onion (Allium ascalonium)
Edwin Permana1*, Kiranti Aulia2, Herman Aziz2, Sri Djangkung Sumbogo Murti3
1 Industrial Chemistry Department, Faculty of Science and Technology, Universitas Jambi, Jambi, 36361, Indonesia
2 Chemistry Department, Faculty of Science and Technology, Universitas Jambi, Jambi, 36361, Indonesia
3 National Innovation Research Agency, Serpong, Tanggerang Selatan
*corresponding Author: [email protected]
Abstract
Article history:
Received 30 December 2022 Revised 3 June 2023 Accepted 2 July 2023
Using fertilizers is one of the efforts to increase crop productivity, but conventional fertilizers tend to be easily leached so it becomes ineffective.
Slow-release fertilizer (SRF) is a modified fertilizer that releases nutrients slowly or gradually so that the use of fertilizer becomes more effective.
SRF can be synthesized by mixing fertilizers with zeolite as a slow-release agent. Because natural zeolite contains many impurities that cover the pores of the zeolite, it is necessary to carry out an activation process to increase the pore capacity of the zeolite so that the process of absorption of nutrients in the SRF becomes more leverage. This study aimed to synthesize NPK S Mg slow-release fertilizer with coconut shell biochar and activated natural zeolite for red onion plants (Allium ascalonium).
Coconut shell biochar was used as a source of potassium. The activation process of natural zeolite was carried out by the desilication method using a basic solution of NaOH as an activator. Based on the results of research using activated natural zeolite on SRF, the surface structure of SRF became more porous, with a porosity percentage of 69.31%. In addition, the use of activated natural zeolites increased the absorption of nutrients in fertilizers.
The use of biochar in SRF increased the percentage of porosity by 66.32%.
The use of coconut shell biochar as a matrix and activated natural zeolite as a slow-release agent in SRF NPK S Mg for red onion plants has succeeded in increasing red onion yields.
Keywords:
activated natural zeolite biochar
red onion
slow-release fertilizer
To cite this article: Permana, E., Aulia, K., Aziz, H. and Murti, S.D.S. 2023. Synthesis of slow-release fertilizer with coconut shell biochar and activated natural zeolite for red onion (Allium ascalonium). Journal of Degraded and Mining Lands Management 11(1):5037-5046, doi:10.15243/jdmlm.2023.111.5037.
Introduction
Red onions are vegetables that are included in horticultural commodities that have been known and used since ancient times. Red onion can be used as a cooking spice, vegetable, food flavoring, or as a traditional medicine (Rismawan et al., 2019). Based on research conducted by Lestari et al. (2020). Traditional fertilizers have soluble properties so that the content in fertilizers cannot be completely absorbed by plants, which can cause several problems, including environmental pollution, health problems, decreased
quality of agricultural products, high production costs and ineffective fertilization time. Therefore, fertilizers are needed that have a pattern of release of nutrients that is in accordance with the pattern of absorption of nutrients by plants. Slow-Release Fertilizer (SRF), is a type of fertilizer that can regulate the release of nutrients from fertilizer.
SRF is one of the modified fertilizers intended to increase the efficiency of the nutrients contained in fertilizers by regulating their release slowly or gradually. In making SRF, several methods can be used, including increasing the size, smoothing the
Open Access 5038 surface of the fertilizer, mixing it with other materials
that are difficult to dissolve (slow-release agents) and covering the fertilizer with certain materials so that the release of fertilizer is slow (Pratomo et al., 2009). SRF can be mixed with slow-release agents because of its porous and good ion exchange properties.
Zeolite is a slow-release agent that is often used (Jumaeri et al., 2019). Zeolite is divided into two, namely, natural and synthetic zeolites. Natural zeolite is a zeolite produced from the process of natural change or zeolitization of tuff volcanic rocks (Mahadilla and Putra, 2013). Natural zeolite has a relatively cheap price compared to synthetic zeolite, and its abundance in Indonesia is quite large. Natural zeolite has drawbacks; namely, natural zeolite contains many impurities, has poor crystallinity, has small pore size, and has non-uniform pore distribution. Therefore, it is necessary to carry out an activation process for natural zeolite through an activation process that can increase the special properties of the zeolite, remove impurities, and change the type of cation in the zeolite to suit the material to be absorbed (Kurniasari et al., 2011; Kismolo et al., 2012). So, the activation process on natural zeolite can increase the ability of zeolite as a slow-release agent in the manufacture of SRF.
The process of SRF synthesis requires several main ingredients to meet the needs of elements needed by plants; one of the main elements needed is potassium. Potassium is a macronutrient that plays a very important role in plant growth and production, especially in onion plants; potassium elements play a role in the photosynthesis process, stimulate plant growth at the beginning of growth, strengthen stems, increase resistance to disease and help provide better tuber yields with quality, and higher shelf life. The most widely used source of potassium in Indonesia today is KCl, with potassium levels reaching 60%
(Gunadi, 2009). However, the availability of KCl in Indonesia is still quite low, and the price is relatively high. Therefore, other materials with a high potassium content are needed to be used as an alternative source of potassium to replace KCl. One of the ingredients that contain high potassium is coconut shell charcoal (biochar). According to Nurida (2014), biochar from coconut shells contains 8.4% K2O. With its high potassium content, biochar can be used as an alternative source of potassium.
This study aimed to synthesize NPKSMg slow- release fertilizer with coconut shell biochar and activated natural zeolite for red onion plants (Allium ascalonium).
Materials and Methods Equipment and materials
The equipment used in this research activity were a blender, mortar and pestle, spray bottle, Erlenmeyer, beaker glass, funnel, filter paper, measuring glass, flask, analytical balance, magnetic stirrer, watch glass,
stirring rod, spatula, pipette drops, thermometer, pH meter, bucket, oven, and moisture analyzer. The instruments used in this study were X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), atomic absorption spectrophotometry (AAS), Brunnaue Emmett Teller (BET). The materials used in this research activity were urea fertilizer, diammonium phosphate (DAP), KCl fertilizer, ZA fertilizer, MgO fertilizer, Bogor natural zeolite, molasses, humic acid, coconut shell biochar originating from the emerging area of South Tangerang City, Banten Province, clay, NaOH and distilled water.
Preparation of materials
In the process of synthesizing SRF NPK S Mg for red onion, the main ingredients used were urea fertilizer, diammonium phosphate (DAP), and KCl fertilizer. In addition to these main ingredients, other ingredients were also added, such as Bogor natural zeolite, ZA fertilizer, MgO fertilizer, clay, and coconut shell biochar (additions were made to the production of SRF NPK S Mg-biochar). All ingredients were mashed with a blender and sieved using a 100 mesh sieve to produce
± 100 mesh fine powder.
Characterization of materials
In this study, the process of making SRF NPK S Mg with a biochar matrix using natural zeolite and activated natural zeolite as slow-release agents were carried out. In this research activity, a comparison of the characteristics of commercial NPK fertilizers was made with Phonska brand (15:15:15), SRF NPK S Mg- non biochar, SRF NPK S Mg-biochar with natural zeolite and SRF NPK S Mg-biochar with activated natural.
Before the fertilizer production process, the raw materials for fertilizers were prepared and characterized. Bogor natural zeolite and biochar were characterized using atomic absorption spectrophotometry (AAS), X-ray diffraction (XRD), and Brunnaue Emmett Teller (BET). Biochar characterization was carried out using AAS, XRD, and SEM-EDX. AAS is used to analyze the content of Potassium (K2O) in coconut shell biochar. XRD to observe the crystallinity structure of coconut shell biochar and determine whether the biochar sample used is biochar or has turned into ash. This is because the biochar used is produced from the traditional combustion process. SEM-EDX was used to observe the morphology and surface structure of biochar, map elements, and determine the percentage of each element in biochar quantitatively.
Bogor natural zeolite was characterized by using Brunnaue Emmett Teller (BET) to determine the surface area of Bogor natural zeolite, and SEM-EDX was used to observe the morphology and surface structure of the natural zeolite and determine the percentage of each element in natural zeolite quantitatively.
Open Access 5039 Activation of zeolite
Bogor natural zeolite was mashed and then sieved to pass 100 mesh. Then, the zeolite was soaked with distilled water for 24 hours, then filtered and dried using an oven at 120 °C for 3 hours. The prepared 20 g of Bogor natural zeolite was mixed with 100 mL of NaOH with various concentrations of 4M, 6M, and 8M. The zeolite was activated using a magnetic stirrer for 1.5 hours at 70 °C, and then the zeolite was filtered and rinsed with distilled water until the pH was neutral.
They were then dried in the oven for 4 hours at 110 °C.
Furthermore, natural zeolite and activated natural zeolite were characterized using BET to determine the surface area. Then, the NaOH concentration produced activated natural zeolite with the largest pore surface area, which was then used as a raw material for activating natural zeolite in the fertilizer production process.
The initial preparation of the Bogor natural zeolite was carried out so that the size of the zeolite becomes uniform or homogeneous and aimed to increase the surface area of the zeolite so that the contact surface area of the zeolite with NaOH would be greater, which would affect the desilication process on the zeolite to be maximized. Furthermore, the refined zeolite was soaked for 24 hours in distilled water, which aimed to remove impurities contained in the zeolite; then the zeolite was dried in an oven at 110 °C for 4 hours which aimed to evaporate the water trapped in the pores of the zeolite.
The prepared zeolite was mixed with NaOH solution with various concentrations of 4M, 6M and 8M NaOH. Zeolite was activated using a Magnetic Stirrer for 1.5 hours at 70 °C. Then, the zeolite was filtered and rinsed with distilled water until the pH was neutral. Then it was dried in an oven for 4 hours at 110
°C which aimed to evaporate the water trapped in the pores of the zeolite so that the pores of the zeolite opened and the active side and adsorption capacity of the zeolite increased. Heating was done to stretch the space between the pores in the zeolite so that the activator could penetrate the small pores and force the dirt and remaining organic matter that was still attached to the surface or pores of the zeolite and push it out of the zeolite pores (Anggara et al., 2013).
The use of NaOH is based on its ability to dissolve certain elements so as to reduce the Si/Al ratio. In addition, the use of NaOH aims to remove certain ions from the zeolite framework and replace them with Na+ ions so that the resulting natural zeolite will be close to the homoionic form (Saidi et al., 2015).
Activation with NaOH base causes a greater adsorption capacity value because Na+ ions will dissolve Si to form sodium silicate so that the zeolite structure becomes more negative. With the zeolite structure being more negative, it can increase the ability of the zeolite to adsorb, especially positively charged cation ions needed by plants such as potassium (K), calcium (Ca), magnesium (Mg), and
others, as well as the adsorption ability of elements from fertilizer will be better.
To determine the specific surface area of natural zeolite and activated natural zeolite, the best method used was N2 gas adsorption to determine the surface area of zeolite. Then, the concentration of NaOH, which produced activated natural zeolite with the largest pore surface area, was then used to activate the zeolite, which was used as a raw material.
Fertilizer production Fertilizer formulation
SRF NPK S Mg-non biochar for red onion was specially made with a formula containing 7.5%
nitrogen, 5% phosphate, 5% potassium, 1.5% sulfur, and 2% magnesium (NPK S Mg 7.5-5-5-1.5-2).
Therefore, the composition of the raw materials in the manufacture of 1 kg of SRF NPK S Mg-non biochar for red onion plants with this formulation required 91.98 g of urea, 108.70 g of DAP, 23.53 g of MgO, 62.50 g ZA, 314.99 g of zeolite, 314.99 g of clay, 83.33 g of KCl. SRF NPK S Mg-biochar with natural zeolite slow-release agent and activated natural zeolite for onion plants were specially made with a formula containing 7.5% nitrogen, 5% phosphate, 5%
potassium, 1.5% sulfur, and 2% magnesium (NPK S Mg 7.5-5-5-1.5-2). Therefore, the composition of the raw materials needed in the manufacture of 1 kg of SRF NPK S Mg-biochar for red onion plants with this formulation required 91.98 g of urea, 108.70 g of DAP, 23.53 g of MgO, 62.50 g of ZA, 314.99 g of zeolite;
314.99 g of clay, 83.33g of KCl and X g of biochar.
The amount of biochar used was known after analyzing the K2O content in the biochar. The stages in its manufacture were granulation, drying, coating, and screening.
Granulation
The fertilizer granulation process was carried out by mixing all the raw materials that had been refined into a bucket gradually according to a predetermined formula. The granulation process was carried out using the wet granulation method by mixing all the ingredients in a bucket and stirring until all the ingredients were completely mixed. During the fertilizer granulation process, the spraying process was carried out with a liquid binder or a binder in the form of a molasses solution with a concentration of 20%.
The granulation process was carried out until fertilizer was obtained in the form of granules or granules measuring 3-5 mm.
Drying
Fertilizers in the form of granules that had been produced were dried. The drying process aimed to reduce the water content contained in the fertilizer. The drying process for the fertilizer was done by drying the granulated fertilizer in the sun until the fertilizer was half dry.
Open Access 5040 Coating
The semi-dry granule fertilizer was coated with humic acid. The coating process was carried out by spraying 20% humic acid (spray coating technique) on semi-dry granule fertilizer until it was evenly distributed over the entire surface of the fertilizer. Then, the fertilizer drying process was carried out again.
Screening
Granular fertilizer that had been dried was sieved using a sieve to obtain fertilizer with a uniform size measuring 3-5 mm.
Characterization of fertilizer
Phonska brand commercial fertilizers, SRF NPK S Mg-non biochar, SRF NPK S Mg-Biochar with natural zeolite, and SRF NPK S Mg-Biochar with activated natural zeolite were characterized using SEM-EDX.
SEM-EDX was used to observe the morphology and surface structure of fertilizers, mapping elements and determining the percentage of each element in fertilizer quantitatively.
Cropping test
The cropping test was using the Bima Brebes seeds variety. Each red onion seed is cut by a third of the tip of the bulb to speed up the shoots. Shallot planting was carried out on a small scale, using a mixture of soil, dolomite and compost in polybags as a planting mediumratio of soil:dolomite: manure is 3:2:1 with 5 different treatments: (F0) without fertilizer (F1) using commercial NPK fertilizer brand Phonska (F2) using SRF NPK S Mg-non biochar (F3), using SRF NPK S Mg-biochar with natural zeolite (F4), using SRF NPK S Mg-biochar with activated natural zeolite. Each treatment was tested using ten polybags.
The cropping test was conducted for 65 days, with the fertilizer application process being carried out 2 times, after 10 days of planting and 30 days of planting. After 65 days, the onion plants were harvested and weighed to determine the weight of the fresh plants produced and then dried for 10 days; after 10 days of drying, a weighing process was carried out to determine the dry weight of the onion bulbs produced. According to Arfiana et al. (2021), the dose of fertilizer for 1 polybag of plants is 0.47 g of fertilizer.
Fertilizer application is carried out in 2 stages;
namely, the first is given at the beginning of the plant after the plants are 10 days old with a dose of 0.236 grams per polybag, and the remainder (0.263 g/polybag) is given at the time of giving the second fertilizer which is done after the plants are 30 days old.
Harvesting is done when the shallot reaches 56 days of age. Next, the drying process of the red onion was carried out for 10 days until the red onion was dry. The parameters observed were plant height (cm), plant fresh weight (g/clump), and bulb dry weight (g/clump) of red onion plants.
Results and Discussion
Characteristics of coconut shell biochar X-ray diffraction (XRD)
Figure 1 shows that the diffractogram pattern of coconut shell biochar had a distinctive peak in the form of a mound in the range 2θ = 23-24o and 42-43o and had a wide and sloping peak intensity. This condition indicates that the coconut shell biochar sample was amorphous. These results are consistent with the research of Kurniasari et al. (2016), which also produced a widened peak in the range 2θ = 23o and 43o, and the research of Caballero et al. (2020) in which the XRD results on biochar produced a diffractogram in the form of widened peaks ranging from 24o and 42o indicating that biochar is composed of amorphous carbon.
Figure 1. Diffraction pattern of coconut shell biochar.
.
Atomic Absorption Spectrophotometry (AAS)
Based on the results of the AAS analysis, it was found that the potassium content in coconut shell biochar reached 6.121 mg/g, with a percentage of K2O content reaching 0.73452%. Due to the relatively low K2O content, this coconut shell biochar was not used as an alternative source of potassium to replace KCl, but coconut shell biochar was used as a matrix in the manufacture of fertilizers.
Scanning Electron Microscopy-Energy Dispersive X- Ray (SEM-EDX)
Figure 2 shows that coconut shell biochar has a surface morphology that is shaped like irregular rocks with non-uniform sizes that are separated from each other.
Based on the results of the analysis with the origin, the percentage of porosity in coconut shell biochar was 70.730%. With a fairly large percentage of coconut shell biochar porosity showing the characteristics of porous biochar, the coconut shell biochar can be used as an adsorbent to capture nutrients in fertilizers and temporarily store nutrients in fertilizers. Based on the EDX results, coconut shell biochar contained 77%
carbon, 17% oxygen, and 6% potassium.
Open Access 5041 Figure 2. Surface morphology of coconut shell
biochar.
Zeolite activation
The results of the surface area characterization of natural zeolite and activated natural zeolite using the BET method are presented in Table 1.
Table 1. Zeolite surface area based on BET results Sample BET surface area (m2/g)
Natural Zeolite 42,2337
Activated Zeolite-4M 28,3760 Activated Zeolite -6M 53,3448 Activated Zeolite -8M 20,1880
Table 1 shows that the surface area of natural zeolite activated with 6M NaOH increased to 53.3448 m2/g and produced the largest surface area of zeolite. So, 6M NaOH was used as a natural zeolite activator in fertilizer production. There was an increase in the surface area of the fertilizer after activation; this was because the activation process with NaOH removed the impurities contained in the zeolite, so it increased the surface area of the zeolite. While the surface area of the zeolite activated with 4M and 8M NaOH decreased. This was thought to be due to the formation of agglomeration in the activated zeolite so that it covered the pores of the zeolite or the deformation of the structure after activation.
Agglomeration is the process of combining small particles into larger particles through a physical binding mechanism. The formation of this agglomeration causes gas adsorption in the SAA test with the best method involving zeolite agglomerates instead of single zeolite particles, causing errors in the interpretation of the specific surface area of a material (Setiawan et al., 2018). The decrease in the surface area of the zeolite after activation with 8M NaOH was thought to be caused by deformation or damage to the structure due to the concentration of NaOH used being too large. The use of NaOH would cause the release of Si from the zeolite framework, and in higher NaOH conditions, it would cause the release of Al from the zeolite framework, which caused damage to the zeolite structure. This result supported the research conducted by Poerwadi et al. (2017) that the use of high NaOH
caused a substantial loss where the partial release of Al3+ occurred, which caused a decrease in surface area.
The activation process with NaOH also affected the shape of the zeolite surface morphological structure.
The result of the zeolite surface morphological analysis with the SEM instrument is presented in Figures 3 and 4.
Figure 3. Surface morphology of natural zeolite with 500x magnification.
Figure 4. Surface morphology of activated zeolite with 500x magnification.
The results of the analysis using the SEM showed that the activation process using an alkaline solution (NaOH) affected the surface morphology of the resulting zeolite (Figures 1 and 2). In general, the morphology of natural zeolite and natural zeolite after activation was very similar. But Figure 1 shows that natural zeolite had a surface morphology that was shaped like irregular rocks with non-uniform sizes separated from each other, while Figure 2 shows that the activation process with NaOH led to the formation of agglomerates of irregular particles with relatively small particle sizes and accumulating on one another.
Based on the results of the analysis with the origin, the percentage of porosity in natural zeolite was 64.499%
and increased after activation to 73.9885%. This shows that after the natural zeolite was activated with NaOH, there was an increase in the porosity of the zeolite surface.The effect of the activation process on the composition of the chemical elements contained in natural zeolite and activated natural zeolite can be analyzed using EDX. The results of the analysis of
Open Access 5042 natural zeolite and activated natural zeolite are
presented in Table 2.
Table 2. EDX results of natural zeolite and activated zeolite.
Element Elements in the Samples (%Wt) Natural Zeolite Activated Zeolite
C 7 7
O 23 24
Na 2 6
Mg 3 3
Al 11 18
Si 44 31
K 66 4
Ca 5 5
Fe - 2
Based on Table 2, after the activation process with NaOH, there was a significant increase in the elemental sodium content where natural zeolite contains 2% sodium but increased after activation to 6%, and there was a decrease in Si content in zeolite is 44% decreased to 31% after the activation process.
According to Kurniawati et al. (2021), activation using the desilication method would cause the removal of silica from the zeolite framework, resulting in mesoporosity, but the micropore size and acidity were maintained. A decrease in the silica content in the zeolite will cause the zeolite to contain more particles so that the adsorption capacity will increase. Also, through this desilication method, there will be an increase in the sodium (Na) content in the zeolite.
Characteristics of fertilizer Brunauer-Emmett-Teller (BET)
The test results using the BET showed that the surface area value of SRF was higher than that of commercial fertilizer (Phonska) at 0.2869 m2/g (Finalis et al., 2019). The SRF NPK S Mg-non biochar produced had a surface area of 10.2774 m2/g, SRF NPK S Mg- biochar with natural zeolite produced had a surface area of 9.4262 m2/g, and SRF NPK S Mg-biochar with activated natural zeolite had a surface area 100 times larger than the Phonska brand of 19.995 m2/g (Table 3). Based on these results, it can be seen that the manufacture of fertilizer in slow-release form (SRF) using zeolite as a slow-release agent provides a larger fertilizer surface area.
Table 3. Surface area of fertilizer based on BET results.
Fertilizer BET Surface
Area (m2/g) SRF NPK S Mg-non biochar 10.2774 SRF NPK S Mg-Biochar-
Natural Zeolite 9.4262
SRF NPK S Mg-Biochar-
Activated Zeolite 19.995
This is because SRF fertilizer uses zeolite, which has a porous structure that will help in increasing the nutrient absorption capacity of the fertilizer so that it will help in the growth and development of red onion plants. The effect of using biochar on fertilizers does not produce a significant effect on the surface area of the fertilizer produced, while the use of activated natural zeolite as a slow-release agent gives very significant results on the surface area produced, where the use of activated natural zeolite can increase the surface area of the fertilizer produced. According to Ngapa (2017), the activation process in natural zeolite will clean the pores of the zeolite from impurities in the form of water molecules and metal oxides. The empty cavities formed on the surface of the zeolite can increase the active surface area so that the adsorption capacity of the zeolite will be greater, which will maximize the absorption of nutrients in fertilizers and soil.
Scanning Electron Microscopy-Energy Dispersive X- Ray (SEM-EDX)
The surface morphology of commercial NPK fertilizers from the Phonska brand, SRF NPK S Mg- Non biochar, SRF NPK S Mg-biochar with natural zeolite, and SRF NPK S Mg-biochar with activated natural zeolite using SEM-EDX are presented in Figures 5, 6, 7, and 8.
Figure 5. Surface morphology of Phonska commercial fertilizer with 500x magnification.
Figure 6. Surface morphology of SRF NPK S Mg- non biochar with 500x magnification.
Open Access 5043 Figure 7. Surface morphology of SRF NPK S Mg-
biochar with natural zeolite at 500x magnification.
Figure 8. Surface morphology of SRF NPK S Mg- biochar with activated natural zeolite with 500x
magnification.
In the Phonska brand commercial NPK fertilizer (Figure 5), the surface morphological structure of the
fertilizer was in the form of long, irregular crystals, while the morphological structure of the SRF NPK S Mg-non biochar surface was in the form of irregular crystals (Figure 6). The use of biochar resulted in a flat crystalline fertilizer surface morphological structure with an irregular shape, a fairly rough surface, and a relatively smaller particle size (Figure 7). Whereas the use of activated natural zeolite showed the morphological structure of the surface of the fertilizer, which formed clumps that stick together, and the morphology of SRF NPK S Mg-biochar with activated natural zeolite had a rough surface. According to Finalis et al. (2019), the morphological structure of the fertilizer is rough due to the sticking of micro-nutrients on the surface of the fertilizer.
The results of the analysis showed that the percentage of porosity in the original Phonska brand NPK fertilizer was 62.082%. In SRF NPK S Mg-non biochar, the percentage of porosity reached 62.3513%.
In SRF NPK S Mg-biochar with natural zeolite, the percentage of porosity reached 66.3150%, and SRF NPK S Mg-biochar with activated natural zeolite, the percentage of porosity reached 69.310%. This shows that the use of coconut shell biochar and activated natural zeolite produces a more porous surface morphological structure of the fertilizer, which will help in increasing the nutrient absorption capacity of the fertilizer and temporary storage of nutrients contained in the fertilizer so that their release becomes slower. The effect of using activated natural biochar and zeolite on the elemental content of fertilizers can be determined through the results of analysis with EDX presented in Table 4.
Table 4. Fertilizers EDX results.
Element Elements In The Samples (%Wt)
NPK Phonska SRF NPK S Mg- non biochar
SRF NPK S Mg- biochar-natural zeolite
SRF NPK S Mg-biochar- activated zeolite
N 5 1 - 2
O 22 12 16 15
Mg 2 1 5 2
P 40 4 11 7
S 13 26 11 19
Cl 8 4 9 3
K 10 26 14 20
Na - - - 1
Al - 3 9 5
Si - 7 17 13
Ca - 13 6 10
Fe - 2 3 3
Data presented in Table 4 show that the composition of the elements contained in Phonska brand commercial NPK fertilizer did not match the percentage of elemental content listed on the fertilizer packaging, which contains 15% nitrogen, 15%
phosphate, and 15% potassium. According to the analysis results with EDX, the percentage of nitrogen, phosphate, and potassium contained in the commercial
NPK fertilizer with the Phonska brand was 5%
nitrogen, 40% phosphate, and 10% potassium. SRF NPK S Mg-non biochar had 1%, 4%, 26%, 26%, and 1% of nitrogen, phosphorus, potassium, sulfur and magnesium, respectively. SRF NPK S Mg-biochar with natural zeolite contained <1%, 11%, 14%, 11%, and 5% of nitrogen, phosphorus, potassium, sulfur, and magnesium, respectively. SRF NPK S Mg-biochar
Open Access 5044 with activated natural zeolite contained 2%, 7%, 20%,
19%, and 2% of nitrogen, phosphorus, potassium, sulfur, and magnesium, respectively. The EDX results show that the elements in the resulting SRF produced did not differ from those in the zeolite, which is a porous material. With the presence of zeolite, the nutrients in the fertilizer can be stored temporarily in the pores of the zeolite to minimize the loss of nutrients in the fertilizer and increase the absorption of nutrients from the fertilizer for plants.
The use of SRF will make the fertilization process more effective by reducing the rate of release or solubility of nutrients from the fertilizer so that the process of absorption of nutrients from fertilizer by plants will be maximized, which in turn increases crop production. Palupi and Widayasunu (2022) reported that the application of slow-release fertilizer (SRF) affected the number of leaves, number of tillers, fresh plant weight, and fresh bulb weight of the Bauji variety of red onion plants. The effect of using coconut shell biochar did not provide significant results when compared to SRF-non biochar. This is because the biochar used contains 77% carbon, 17% oxygen, and 6% potassium, so it does not significantly affect the fertilizer's NPK S Mg content. While the effect of using activated natural zeolite can be seen that with the use of activated natural zeolite, nutrient absorption in fertilizers is better compared to SRF with natural zeolite. This is because after the activation process is carried out on the zeolite, there is the removal of impurities on the surface of the zeolite so that the pores in the zeolite become more open and the ability of the zeolite to capture nutrient elements in the fertilizer is maximized.
Cropping test
After cropping for 65 days, the following results were obtained (Figure 9). Based on these results, it can be seen that the use of fertilizer could increase plant height growth by 3.37%. Besides that, the use of slow- release fertilizer (SRF NPK S Mg-non-biochar) could increase the height growth of red onion plants, which can be seen in the ratio of plant height to the F1 and F2 treatments where the F2 treatment was able to increase plant height by 7.3% compared to plants treated with commercial fertilizer of Phonska brand (F1). The use of biochar in SRF NPK S Mg-biochar fertilizer with natural zeolite (F3) was also able to increase plant height by 2.28% compared to plants treated with SRF NPK S Mg-non biochar (F2) fertilizer. The use of activated natural zeolite in fertilizer (F4) can also increase the height growth of shallot plants by 1.49%
when compared to treatment with SRF NPK S Mg- biochar fertilizer with natural zeolite (F3). The fresh plant weight produced in treatments F0, F1, F2, F3 and F4 were 60.9 g; 70.3 g; 78.9 g; 85.4 g and 89.3 g. Based on these results, it can be seen that the use of fertilizer could increase the fresh plant weight by 15.43%.
Besides that, the use of slow-release fertilizer (SRF NPK S Mg-non biochar) could increase the fresh plant weight of red onion, which can be seen in the ratio of fresh plant weight in the F1 and F2 treatments, where the F2 treatment was able to increase fresh plant weight by 12.23% compared to plants treated with commercial fertilizer of Phonska brand (F1). The use of biochar in SRF NPK S Mg-biochar fertilizer with natural zeolite (F3) was also able to increase fresh plant weight by 8.24% compared to plants treated with SRF NPK S Mg-non biochar (F2) fertilizer.
Figure 9. Cropping test results.
The use of activated natural zeolite in fertilizer (F4) could also increase the fresh weight of shallot plants by 4.57% when compared to treatment with SRF NPK S Mg-biochar fertilizer with natural zeolite (F3). The mean yields of dry tuber weight produced in the F0, F1, F2, F3, and F4 treatments were 51.6 g, 64.5 g, 70.2 g, 79.4 g, and 80.1 g, respectively. Based on these
results, it can be seen that the use of fertilizer could increase the dry tuber weight by 25%. Besides that, the use of fertilizer in the slow-release form (SRF NPK S Mg-non biochar) could increase the dry bulb weight of red onion, which can be seen in the ratio of dry tuber weight to treatment F1 and F2 where the F2 treatment was able to increase dry plant weight by 8.84%
23.7 24.5 26.3 26.9 27.3
60.9 70.3 78.9 85.4 89.3
51.6
64.5 70.2 79.4 80.1
0 20 40 60 80 100
F0 F1 F2 F3 F4
% increase
Treatments Cropping Test Results
Plant Height (cm) Fresh Plant Weight (gr/Clump) Dry Plant Weight (gr/Clump)
Open Access 5045 compared to plants treated with commercial fertilizer
brand Phonska (F1). The use of biochar in SRF NPK S Mg-biochar fertilizer with natural zeolite (F3) was also able to increase dry plant weight by 13.11% compared to plants treated with SRF NPK S Mg-non biochar (F2) fertilizer. The use of activated natural zeolite in fertilizer (F4) can also increase the dry bulb weight of red onion plants by 0.89% when compared to treatment with SRF NPK S Mg-biochar fertilizer with natural zeolite (F3).
Conclusion
Characteristics of coconut shell biochar can be identified with several instruments, including XRD, AAS, and SEM-EDX. The XRD results of coconut shell biochar contained mounds in the range 2θ = 23- 24o and 42-43o and had a wide and sloping peak intensity, indicating that the coconut shell biochar sample was amorphous. The potassium content in coconut shell biochar reaches 6.121 mg/g, with a percentage of K2O content reaching 0.73452%. In addition, the content of other elements contained in coconut shell biochar is 77% carbon, 17% oxygen and 6% potassium. Coconut shell biochar has a surface morphology that is shaped like rock crystals with irregular and non-uniform sizes separated from each other with relatively small particle sizes with a porosity percentage of coconut shell biochar reaching 70.730%. The use of coconut shell biochar makes the surface of the fertilizer more porous, where in SRF NPK S Mg-non biochar the percentage of porosity reaches 62.3513% and increases after the addition of biochar to fertilizer (SRF NPK S Mg-biochar with natural zeolite) the percentage of porosity reaches 66.3150 %; however, the use of coconut shell biochar did not have a significant effect on the elemental composition of the fertilizer. The use of activated natural zeolite resulted in a more porous surface structure of the fertilizer, where in SRF NPK S Mg- biochar with natural zeolite, the percentage of porosity reached 66.3150%, and in SRF NPK S Mg-biochar with activated natural zeolite it increased to 69.310%.
In addition, the use of activated natural zeolite can increase the absorption of nutrients in fertilizers better.
This can be seen in the percentage of NPK S Mg elements in SRF NPK S Mg-biochar with activated natural zeolite is higher than SRF NPK S Mg-biochar with natural zeolite. The use of coconut shell biochar as a matrix and activated natural zeolite as a slow- release agent in SRF NPK S Mg for shallot plants have succeeded in increasing shallot yields when compared to treatment without fertilizer, Phonska brand commercial fertilizer, SRF NPK S. Mg-non biochar and SRF NPK S Mg-non biochar with natural zeolite.
Acknowledgments
The authors thank the Faculty of Science and Technology, Universitas Jambi, and the National Innovation Research
Agency for financial support. This project could be achieved through the collaboration program of the two parties above.
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