Utilization of organic ameliorants and fertilizers to increase Entisol total N through axis system fertigation in vertical cultivation

The high porosity and low organic matter content of Entisol are the reasons that Nitrogen (N) is easily leached and lost due to evaporation. Application of organic ameliorants and fertilization is expected to increase total N in Entisol. To find out the effect of organic ameliorants and fertilizers on increasing total N through axis fertigation in vertical cultivation, this study was conducted using a divided plot design. The organic ameliorant treatment consisted of soil (A1) as control, A2 (soil:biochar)(1:1), A3 (soil:compost)(1:1), A4 (soil: biochar:compost)(1:1:1), while the fertilizer treatment consisted of P1 (urea), P2 (liquid organic fertilizer [LOF]), P3 (urea + liquid organic fertilizer[LOF]), P4 (urea + nitrogen fixing-bacteria[NFB]), P5 (liquid organic fertilizer[LOF] + nitrogen-fixing bacteria[NFB]), and P6 (Urea + liquid organic fertilizer[LOF] + nitrogen-fixing bacteria[NFB]). The results showed that the increase in total N occurred after the addition of organic ameliorant and fertilizer. The single treatment with ameliorant ratio of 1:1:1 (soil: biochar: compost) (A4) showed the highest increase in total N, which was 1.08% and was significantly different from the other treatments. The single treatment of fertilizer type with a combination of 3 types of fertilizer namely urea + LOF + NFB (P6) produced the highest total N (0.95%).


Introduction
Entisol is a young soil that has low nutrient availability and water-holding capacity and has a shallow solum [1].Entisol's high soil porosity and low organic matter content [1] cause the nutrient element Nitrogen (N) being easily leached and lost due to evaporation.Nitrogen is an essential nutrient for plants, so a solution is needed to overcome the N problem so that plants can grow optimally.The use of appropriate agricultural technology can increase soil fertility.The application of soil ameliorant materials, namely compost, can improve the physical, chemical, and biological properties of the soil.The availability of N nutrient was reported to increase with the application of compost [2].Compost is easily decomposed so the function does not last long, Therefore other materials are needed to support the function of the compost over a long period.Biochar can be an alternative to complete that function.Biochar has the characteristic that it is difficult to decompose due to incomplete combustion.The advantage is that it lasts longer in the soil so it is very good for improving soil quality and plant growth on less fertile marginal lands [3].Apart from ameliorants, soil N can be increased by adding fertilizer.
IOP Publishing doi:10.1088/1755-1315/1302/1/012023 2 Urea fertilizer is an inorganic fertilizer that is often used by people, but its use for a long time can cause soil acidity and pollute the aquatic environment [4].Thus, organic fertilizer can be an option to increase soil N. Liquid organic fertilizer (LOF) is an organic fertilizer in the form of a liquid or solution containing nutrients that are beneficial for plant growth.Previous research [5] reported that LOF application could increase total N and available N. In addition to added organic matter, efforts to increase N can be carried out by utilizing Nitrogen -Fixing Bacteria (NFB) as a biological fertilizer that can fix nitrogen in the air to minimize the use of conventional N fertilizers [6].These fertilizers can be applied to vertical plant cultivation.Apart from requiring little space [7], verticulture cultivation can be an option for relatively heavy soil management, especially in Timor which has rocky soil.Verticulture cultivation is usually known as urban farming, is an efficient way of land use.This research has compiled the plants are grown one above another around the surface of upright cylindrical units housing a nutrient supply [8].The success of verticulture cultivation is determined by the composition of planting media [9].The application of inorganic and organic fertilizers can be given using a wick fertigation system.
Wick system fertigation is very effective in providing nutrients and their uptake by plant roots [10].The wick, which is placed in the middle of the planting medium in the verticultur cultivation using pipe, functions to channel water and nutrients to the plants [11].The reservoir at the bottom functions to continuously wet the wick based on capillarity theory so that the planting medium is always moist with water and nutrients provided through fertilization [12].The purpose of this study was to determine the best type of organic ameliorant and fertilizer that can increase total N Entisols through axis system fertigation in vertical cultivation.

Materials and Methods
The experiment was conducted in a farm located in Sasi sub-district, Kefamenanu City District, North Central Timor Regency, East Nusa Tenggara Province held from August -October 2023.This research used Entisol with treatment in the form of ameliorant and fertilizer.There are 2 types of ameliorant used, namely biochar and compost.The biochar used comes from rice husks which are burned into charcoal, while the compost is made from forage in the surrounding environment and household waste.Meanwhile, the fertilizers used are urea, LOF which comes from forage and household waste, and NFB which comes from isolation in the rhizosphere of gude beans.This type of ameliorant was applied to the verticulture cultivation of pakchoy plants at harvest age of 35 HST.Soil and ameliorant are put into the perforated paralon.Meanwhile, in the middle of the paralon there is a fertigation axis for applying fertilizer.A fertilizer application with a frequency of once every 2 weeks according to urea treatment 1 g/L (17), LOF 40 mL/L (18), NFB density 10 8 CFU/mL 10 mL.
Table 1.The combination of treatments using the composition of the planting medium and the type of fertilizer Types of ameliorants in the planting medium Type of fertilizers A1 (soil) A2 (soil: biochar) (1:1) This research used a Divided Plot Design with 2 factors namely the types of fertilizers and ameliorants in the planting medium which were repeated 3 times.Each replication has 24 treatments so that total of 72 combinations is obtained treatment.The combination of treatments can be seen in Table 1.The soil chemical parameters observed were pH, C-organic, Cation Exchange Capacity (CEC), and total N. Research data analysis used analysis of variance and Duncan's advanced test (Program SAS for Windows version 9).

Initial Soil Analysis
Preliminary data on the planting media before planting pakcoy and applying fertilizer are shown in Table 2. Soil pH without ameliorant treatment (A1) or with ameliorant treatment (A2, A3, and A4) is included in the neutral category.Carbon organic data for treatments A1 (soil) and A2 (soil:biochar) were very low, while A3 (soil compost) was low, and A4 (soil: biochar + compost) was very high.Soil that was added with ameliorant biochar and compost (A4) with a ratio of 1:1:1 had a very high C-organic content due to the contribution of 2 types of organic matter namely biochar and compost in one planting medium.The CEC of the A1 treatment that contains only soil showed a high value, then when it was given additional ameliorants, A2, A3, and A4, the CEC value changed to very high.While the total N soil data without the addition of ameliorant (A1) had very low criteria, then when given additional ameliorant it increases, namely A2 was moderate criteria, A3 was low, and A4 was high criteria.Initial LOF analysis showed that the C-organic content was 1.82% and was included in the low criteria, while the N-total was 2.05%, which was included in the very high criteria.Preliminary data on the activity of nitrogen-fixing bacteria in the planting medium before fertilization (Table 3) shows that the highest NFB density (4.16465x10 9 CFU/ml) was found in treatment A4 (soil: biochar+ compost) while A1, A2, and A3 showed relatively the same density, namely around 1.5×10 9 CFU/ml.

pH
Table 4 shows that there was no interaction between the type of fertilizer and ameliorant added to soil pH.The single factor of fertilizer type also showed no significant effect.Meanwhile, the single factor of growing media added with ameliorant showed a significant effect on soil pH.The highest soil pH (7.84) was found in treatment A1 (soil) which was significantly different from A2 and A4.Meanwhile, the lowest soil pH was found in treatment A4 (7.63) compared to other treatments.This can be caused by added ameliorant decomposes and releases its organic acids.Apart from that, the NFB density in A4 is higher than the others (Table 3).The presence of Nitrosomonas and Nitrobacter bacteria can reduce soil pH in the nitrification process [13].However, the pH in all treatments included in the slightly alkaline category.

C-organic
A single treatment of ameliorant and fertilizer had a significant effect on C-organic and in general there was an increase in C-organic content (Table 5) compared to the initial data (Table 2).In the ameliorant treatment, the highest C-organic content was found in treatments A2 (soil:biochar ) and A4 (soil: biochar+ compost), by 8.78% and was significantly different from the other treatments.Furthermore, in the treatment the highest type of C-organic fertilizer was found in the P2 (LOF) treatment.The increase carbon in the soil came from added organic material undergoing the decomposition process.Previous research results reported that an increase in C-organic occurred when biochar and compost were added [2] and LOF [14].

Cation Exchange Capacity (CEC)
Based on Table 6, a single treatment of both ameliorant and fertilizer has a significant effect on increasing CEC.Treatment A2 (soil: biochar) produced the highest CEC and was significantly different from the others.Biochar has many active functional groups on its surface which are negatively charged such as -COOH and -OH which can react with cations in the soil so that it can increase CEC [15].Biochar was reported to be able to increase CEC compared to treatment without biochar ranging from 17 to 220% [16].A single treatment of P6 fertilizer (urea+LOF+NFB) produces the highest CEC value because LOF contains humic and fulvic acids which have negatively charged functional groups such as carboxyl and carbonyl [17].Research [18] reported that LOF from banana stems and coconut husks increased CEC.  7, a single treatment of both ameliorant and fertilizer had a significant effect on increasing total N.The more various ameliorants added (A4) in this study, the higher total N content reaching by 1.08% and included in the very high category based on the Soil Research Institute [19].
When compared with the initial N-total data (Table 1), the final N-total data after harvesting (Table 4) shows an increase.The N contribution provided by nitrogen-fixing bacteria, which were reported to be quite dense in initial observations (Table 3).The presence of nitrogen-fixing bacteria plays a role in fixing nitrogen in the air so that it can increase the total N in the soil.Research [20] reported that N-total increased by 111.76 % in soil applied with NFB compared to without NFB application.In addition, biochar can absorb NH 4 + and NO 3-thereby reducing the leaching and evaporation of N from the soil [21].Furthermore, the fertilizer treatment which combined 3 types of fertilizers namely urea, LOF, and NFB (P6) gave the highest total N content, namely 0.95% (very high category [19]) and was significantly different from other treatments.This is presumably because the A4 treatment is a complete fertilizer combination from this study, namely urea with a high enough N content can increase total N [22], LOF based on initial analysis contains very high total N, and NFB plays a role in nitrogen fixation in the air [20].

Conclusion
The increase in total N occurred after the addition of organic ameliorant and fertilizer.The single treatment with ameliorant ratio of 1:1:1 (soil : biochar : compost) (A4) showed the highest increase in total N, which was 1.08% and was significantly different from the other treatments.The single treatment of fertilizer type with a combination of 3 types of fertilizer namely urea + LOF + NFB (P6) produced the highest total N (0.95%).

References
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Table 2 .
Chemical properties data of soil at the beginning of ameliorant treatment before fertilization * Criteria based on the Soil Research Institute(2009)

Table 3 .
Initial data on the density of nitrogen-fixing bacteria in the planting medium before fertilization

Table 4 .
Soil pH due to application of ameliorant and fertilizer

Table 6 .
Cation Exchange Capacity due to the application of ameliorant and fertilizer (cmol[+]/kg )

Table 7 .
Total N due to application of ameliorant and fertilizer (%)