Impact of chemical fertilizer on soil fertility of oil palm plantations in relation to productivity and environment

Indonesia produces around 45 MT of CPO in 2020. It is predicted that the demand of world palm oil will remain. Most of the oil palm plantations are grown on acidic soils with low fertility levels, such as Peat soils, Podzolic soils, and Acid sulfate soils. The domestic demand of phosphate and Kalium fertilizer still fulfilled by importation. Production of oil palm had depend on this fertilizer. Various research results have found that fertilizing oil palm using chemical anorganic fertilizers, especially Urea, TSP, KCl and Kieserit, has produced fresh fruit bunches which are quite high and profitable. Fertilizing oil palm crops requires a very large cost of around 30% of production costs. Currently, non-subsidized chemical fertilizers are rocketing, which is very burdensome for oil palm farmers. Some research results indicate that the continuous use of chemical fertilizers in oil palm plants causes to the land degradation. The use of organic fertilizers can improve sour and less fertile land, can increase the weight and number of oil palm fruit bunches. This paper aims to examine the impact of the use of chemical fertilizers on oil palm fruit production, as well as provide alternative organic fertilizers which sources are mostly around plantations.


Introduction
Oil palm is an important plantation crop that produces palm oil as the main source of basic ingredients for making food oil, industrial oil and biofuel.Palm oil is currently the largest source of vegetable oil in the world.Indonesia produces around 45 MT of CPO in 2020 [1].World demand for palm oil is expected to continue to increase in line with population growth, food and chemical industries [2].In the process of production and industrial processing, oil palm plantations are also able to create opportunities and employment, especially for rural communities while improving the welfare of the community [3].
Well-cultivated oil palm produces palm oil whose productivity can be up to six times higher than oil produced by rapeseed.In addition, the energy balance, which is expressed by the ratio of energy output to input, in oil palm plantations is higher than other oil-producing crops.These characteristics strongly support the development of oil palm as a renewable energy source in the future.On most lands, large amounts of inorganic fertilizers are required to ensure a high level of productivity, but this can be accounted for because oil palm is very efficient in producing renewable energy [4].The area of oil palm plantations in Indonesia based on the results of the 2021 reevaluation is 16,833,985 ha [5], while based on data from the Coordinating Ministry for Economic Affairs for 2019 it is 16,381,415 ha [6].
Most of the oil palm plantations are grown on acidic soils with low fertility levels, such as Peat soils, Podzolic soils, and Acid sulfate soils.These lands are in dry land or in wet land that has been drained.Each type of soil has a very different soil capability in providing nutrients and depends on the amount of available nutrients, the presence of fixation and mobilization processes, and the ease with which nutrients are available to reach the root zone of plants.In addition to acidic and infertile soil conditions, oil palm is a plant that requires a lot of nutrients derived from chemical fertilizers (inorganic) to produce high fresh fruit bunches (FFB).Oil palm plants require high amounts of fertilizer, considering that 1 tonne of FFB produced is equivalent to 6.3 kg of urea, 2.1 kg of TSP, 7.3 kg of KCl, and 4.9 kg of kiserite [7].Several research results indicate that the continuous use of chemical fertilizers on oil palm causes land degradation which is indicated by the decrease in organic C content to very low (<2%).
Currently, the subsidized chemical (inorganic) fertilizers available for oil palm are no longer available.In the Regulation of the Minister of Agriculture No. 10 of 2022 [8], concerning the Procedure for Determining the Allocation and Highest Retail Price of Subsidized Fertilizers in the Agriculture Sector, it is stated that subsidized fertilizers are only limited to nine main commodities, namely rice, corn, soybeans, chilies, shallots, garlic, sugarcane, coffee.and cocoa.In addition, subsidized fertilizers are only focused on two types of fertilizers, namely Nitrogen (N) Phosphorus (P) and Potassium (K) and urea.In this regard, a solution is needed to overcome this, one of which is the use of organic fertilizers derived from palm oil waste around the plantations.Nowadays, the demand of chemical fertilizer increasing, as a global reaction in anticipating of food crisis due to extreme weather and the impact some conflict such as in the USSR and Ukraine.Indonesia is not excluded and in order to maintain the food crop production, the government of Indonesia continue to keep fertilizer subsidy policy in order to helping the farmer to maintain its food crop production in high productivity level and produce food crops in affordable price.In order to prevent food shortage worldwide and maximize crop yield, large amounts of chemical fertilizers have been applied to arable fields over the past few decades [9].
However, some research found the fertilizer subsidy causing serious problems including for some cases the farmer paid higher price compare to maximum retail priced sets by government; the policy creating disparity price both with international market and with the price of fertilizer for non-food sector in domestic market, creating the leakage problem and abused of chemical fertilizer create the environment problem.The excessive use of chemical fertilizers has led to several issues such as serious soil degradation, nitrogen leaching, soil compaction, reduction in soil organic matter, and loss of soil carbon.In addition, the efficacy of chemical fertilizers on crop yield has been decreasing over time [10].
In the fertilization process, farmers often use certain brands.However, planters do not pay attentionto the impact of prolonged use of chemical fertilizers resulting in a dense and hard soil structure (no longer loose) the soil is unable to absorb water so that the soil pH becomes acidic.When the pH of the soil is acidic, the decomposition of soil organic matter becomes disturbed, microorganisms beneficial to the soil and plants become wiped out or die.As the effort of fertilizing on farmers' land has to consider many factors.Two of them have to considered are the amount of nutrients uptaken by plant and the availability of nutrients in the soil [7].
In the process of oil palm cultivation, the use of fertilizers is a crucial factor.There are many things that must be considered in applying fertilizer to oil palm plants, i.e the dosage, type, to the material contained in the fertilizer.For example, even though we use premium quality fertilizer, we still can't be careless in using it.Because, we also need to consider aspects of fertility, soil conditions, plant growth, plant productivity, and the variety of plants used.Different varieties and soil conditions will also differ in fertilizer needs for these plants.Therefore, fertilizer application cannot be done carelessly if we expect quality and maximum yields.Whatever type of fertilizer we use, we must apply it according to the recommendations for use.Too much urea fertilizer is applied to the soil, then the soil will become acidic.Acidic soils result in the absorption of certain nutrients becoming inhibited.In addition, the threatened survival of microorganisms residing in the soil.
This paper aims to examine the characteristic of the acid soil in Indonesia; the impact of the use of chemical fertilizers on oil palm fruit production, as well as provide alternative organic fertilizers which sources are mostly around plantations.

Characteristic of acid soils in Indonesia
Most of the oil palm plantations are grown on soils that are acidic and have low fertility levels such as Peat soils, Podzolic soils, and Acid sulfate soils.The area of oil palm plantations on peat soils (Organosols) is estimated to be around 4.0-4.5 million hectares, and about 2.5-3.5 million hectares of oil palm plantations occupy non-peat swamp land [11].Non-peat swamp land generally consists of acid sulfate land and lebak swamp land.
Ultisols or Podzolic soil is a soil with a very wide distribution (25% of the total land area of Indonesia) located in a wet climate, has a deep soil cross section and low to moderate cation exchange capacity so that this soil has an important role in the development of dryland agriculture including palm oil in Indonesia [12,13].

Peatlands
Peat soils based on criteria in Soil Taxonomy [14] and the World Reference Base for Soil Resource [15] are classified as Histosols.Meanwhile, based on the Indonesian National Soils Classification [16] it is classified as Organosols.Organosols are defined as those that have a horizontal H > 50 cm thick (if organic matter consists of Spaghnum or moss > 60 cm or has a bulk density of < 0.1 gr/cm3) from the soil surface, or a cumulative 50 cm inside the upper 80 cm of the upper layer; the thickness of the H horizon may decrease if there is a layer of rock or rock fragment material filled with organic matter among them.Peat thickness criteria mostly use a minimum thickness of 50 cm [16].Theselected 50 cm thickness is derived from average requirements of 40 cm (sapric) and 60 cm (fibric).
Based on the results of mapping using various methods, peat area from 1976 to 2019, continued to decline.According to Soepraptohardjo and Driessen (1976) the peat area is estimated at 17 million hectares [17].Then Driessen (1978) stated that peat in Indonesia covers an area of 16.35 million hectares [18].Furthermore, the BBSDLP (2011) published that peat in Indonesia covers an area of 14.93 million hectares [19].
The characteristics of peat soil are very unique and very different from mineral soils.These characteristics are related to the constituent material, thickness, maturity and the environment in which it is formed.The specific characteristics of peat soil are: (1) it is easy to experience irreversible drying, i.e. when the peat dries with a moisture content of <100% (based on dry weight), cannot absorb any more water when it is wetted, (2) it is easy to dry out.subsidence, which occurs due to peat compaction, decomposition and erosion processes, (3) has a low bearing capacity to pressure, (4) has a low nutrient content, both macro and micro nutrients so that it is relatively infertile, and (5) has a limited number of microorganisms [20].The results of research and mapping of peat in Bangka Island, North Kalimantan Province, Papua Province and Jambi Province show that the fertility level of peat soil is low [21,22,23,24].Table 1 shows the chemical characteristics of peat soil planted with oil palm in Jambi Province.

Podzolic soils
Podzolic soils or Ultisols are the most widely distributed land in Indonesia, covering an area of 45,794,000 ha or about 25 percent of the total land area in Indonesia.This Podzolic soil is widely spread, has a flat to mountainous area [25].Highly weathered and weathered ultisols are often used for expansion of agricultural production in Indonesia.The land use of this land on the islands of Sumatra, Kalimantan, Sulawesi and Papua is in the form of fields, oil palm plantations, rubber plantations and industrial forest plantations.Due to the problems mentioned above, on a farmer scale economic constraints are one of the causes of this land not being managed properly.The chemical characteristics of several Ultisols that developed from several parent materials are presented in Table 2.However, if Ultisols soil is managed properly, its productivity can be increased.The use of lime and fertilizers is needed to overcome the problems of acidity and soil fertility so that crop production in highly weathered soils (Ultisols) in Sitiung, Indonesia can be increased [26].Research to increase the productivity of Ultisols soil by applying lime, P fertilization and organic matter from manure has increased maize seed yield and fodder biomass by almost 700% compared to standard fertilization [28].Meanwhile, fertilization of N, P, K and Mg in oil palm plants can increase up to the limit of potential production of 30 tons per ha [7].

Acid sulfate soils
Acid sulfate soils is soils in the tidal swamp area where the soil contains pyrite compounds (FeS2).The main problem in the development of tidal swamp land is the presence of potential and actual acid sulfate soils which cover an area of 4.34 million ha and 2.37 million ha, respectively [19].Under flooded conditions, these compounds are stable, but the acidification process occurs when the aeration reaches the pyrite layer, so that the pyrite undergoes oxidation releasing sulfuric acid which causes the pH which was originally around neutral to drop to 3.5 or less [29].The chemical and physical characteristics of the actual and potential acid sulfate soils in Kalimantan and Sumatra are presented in Table 3.The area of this acid sulfate land is increasing along with the degradation of swamp land which has a layer of sulfidic material underneath.Experience shows that the clearing of acid sulfate land, including for the establishment of oil palm plantations, is always accompanied by the construction of waterways for transportation and drainage or irrigation purposes in the area.But in reality, water management cannot be controlled properly, so that the groundwater level drops below the surface of the pyrite layer, especially during the dry season.This results in oxidized pyrite compounds which produce sulfuric acid which causes the soil pH to be very low.The decrease in soil pH has a negative impact on the chemicalproperties and microbial activity of the soil [30].The problem that arises as a result of the acidification process is that if toxic compounds or elements are not removed from the root environment, plant growthwill be hampered.

Chemical fertilizers
Palm oil fertilization aims to add nutrients that are lacking or not available in the soil, these nutrients are needed by plants for vegetative and generative growth in order to obtain optimal fresh fruit bunches.Fertilization is an effort to provide sufficient nutrients to encourage healthy vegetative growth and the production of fresh fruit bunches to reach maximum productivity.The effectiveness of fertilization is related to the percentage of fertilizer nutrients absorbed by plants.Fertilization is said to be effective if most of the fertilizer nutrients are absorbed by plants, while the efficiency of fertilization is related to the relationship between costs (fertilizer materials, work tools, and wages) with the level of production produced [32].
To support the growth of oil palm, both in the nursery area and in plants that are already in production, fertilization is required, both in the form of macro fertilizer and micro fertilizer.One of the commonly used macro fertilizers is urea fertilizer.Urea fertilizer is an inorganic fertilizer which is also an N (nitrogen) fertilizer.Urea is a hygroscopic fertilizer.The main function of urea fertilizer is to increase plant growth and leaf green [33].

Urea fertilizer for oil palm crops
This fertilizer is often chosen because it helps plant growth.Many also wonder why urea fertilizer has an important role for the growth of a plant.This is because of its high nitrogen content so it has several advantages for plants.Then what are the benefits of urea fertilizer for oil palm plants?Here are some explanations [34].

Optimizing oil palm plant growth
Urea fertilizer with a high nitrogen content is proved to be very suitable to complement the nutrient needs of palm oil during its growth process.It should be noted that some oil palm grows on peatlands with a low content of nutrients and minerals.With sufficient nutrition, oil palm plants can grow very optimally in the area.

Role in the process of photosynthesis
The next advantage of urea fertilizer is to help plants in carrying out the process of photosynthesis.This is because the leaves of this plant can produce chlorophyll.In addition, urea fertilizer can make the leaves greener than usual due to chlorophyll.Chlorophyll or known as the green substance of leaves is indispensable as one of the photosynthetic materials in plants.

Increasing palm oil productivity
Productivity is an important thing when cultivating oil palm crops.By using urea fertilizer, palm oil productivity can be increased, starting from the number of crops and the quality of the oil palm fruit produced.Palm oil can produce abundant yields because it is assisted by nitrogen in urea fertilizer and can be trusted as a soil nutritional supplement.

Dosage and how to apply urea fertilizer to oil palm plants
With the various benefits of urea fertilizer for oil palm, farmers must understand that in terms of fertilizer applications, it is not only the selection of fertilizers that can make the oil palm fruit grow well.Fertilizing should be done correctly so as not to damage the soil.Therefore, it is necessary to pay attention to how to fertilize properly and the selection of doses that correspond to the age of the plant.In addition, there are several fertilization methods to maximize the benefits of urea fertilizer for oil palm.Even farmers need to adhere to the dosage relating to the age of the oil palm plant [34].The following is the dosage of urea fertilizer for oil palm plants: 1. Immature plants When the crop is not yet yielding, the farmer needs to provide additional nutrition for the planted crop.A different amount of urea fertilizer is required for each plant development, here are the dosages by different type of soil: x Podzolic soil 9 When the plant is still 1 month old, apply urea fertilizer to plants as much as 0.0047 kilograms per plant.9 When the plants begin to be 3, 5, and 8 months old, urea fertilizer is applied as muchas 0.1175 kilograms per plant, respectively.9 Then when the plants start to be 12, 13, 20, 24 months old, urea fertilizer is applied asmuch as 0.235 kilograms each per plant.9 Then when the plants start to be 28 and 32 months old, urea fertilizer is given as muchas 325 kilograms per plant, respectively.
x Alluvial soil 9 When the plant is 12 months old, urea fertilizer is applied as much as 0.1175 kilogramsper plant.9 For other types of age, almost the same dosage is applied with Podzolic soil.
x Entisol soil 9 When the plant is only 1 month old, 0.070 kilograms of urea fertilizer is applied per plant.9 Then when the plants begin to be 3 months old, urea fertilizer is applied 0.1175kilograms per plant.9 Then when the plants are 5, 8, 12, 14, 17, 20, 24, 28 months old, urea fertilizer is appliedas much as 0.235 kilograms each per plant.9 After the plants are 32 months old, urea fertilizer is applied as much as 325 kilograms each per plant.

Productive plants
Meanwhile, for oil palm plants that have already produced, dosage are given with the following time: x Peat Soil 9 When the plant is 3-8 years old, 2 kilograms of urea fertilizer is applied per plant.9 When the plants are 9-13 years old, urea fertilizer is applied as much as 2.5 kilogramsper plant.9 When the plant is 14-20 years old, urea fertilizer is applied as much as 1.5 kilogramsper plant.9 When the plant is 21-25 years old, urea fertilizer is applied as much as 1.5 kilogramsper plant.After determining the dosage, the next thing to pay attention to is how to fertilize.The most effective way to apply urea fertilizer to oil palm is to sprinkle it on a flat circle placed around the plant.The following are fertilization steps so that the benefits of urea fertilizer for palm oil are more optimal: x Before applying fertilizer, the planting area should be cleaned of all weeds and grass plants.
Apply urea fertilizer from the center of the plant to the weed section.
x Fertilizing is recommended to apply during the rainy season.This is because the fertilizer is easily absorbed by the soil in wet conditions.

Potential impact of urea fertilizer use on palm oil
Urea fertilizer does provide nutrients more quickly to plants.However, 30-40 percent of urea fertilizer applied is often wasted due to evaporation due to the scorching sun and/or due to drift due to rain, according to research that has done [34].Excessive use of urea fertilizer will damage the plant and build up the concentration of toxic salts in the soil which will eventually cause chemical imbalances in the soil and can change the pH natural soil.In addition, excessive use of urea fertilizer will also cause various problems, such as: Plants are susceptible to pests and diseases, if urea fertilization is carried out excessively, plants will be susceptible to pests and diseases.Too much urea fertilizer is applied to the soil, then the soil will become acidic.Acidic soils result in the absorption of certain nutrients becoming inhibited.In addition, the threatened survival of microorganisms residing in the soil.
To minimize these impacts, it would be nice to balance the use of urea fertilizer with other fertilizers such as organic fertilizers with the right formulation.The balance of fertilizer use certainly does not only aim at the growth process, but also for good production because all plant needs are met and can be neutralizes the negative properties of urea fertilizer.
The adverse impact of prolonged use of chemical fertilizers results in a dense and hard soil structure (no longer loose) the soil is unable to absorb water so that the soil pH becomes acid.When the pH of the soil is acidic, the decomposition of soil organic matter becomes disturbed, microorganisms beneficialto the soil and plants become wiped out or die.Damaged agroecosystems are an environment that is very favored by oil palm pests and diseases of oil palm plants.In this state, too, disease pests are more resistant to extreme environments with high plant killing power.The plantation will get worse if it is not saved immediately.The key to a healthy plant, if the soil and root are also healthy.Quality fertilizeris a fertilizer that can improve soil acidity and stimulate root so that the oil palm fertilization process can run well.

Phosphate fertilization for oil palm
The application of fertilizers is intended to meet nutrient needs that cannot be provided by the soil.Nitrogen (N), phosphorus (P) and potassium or kalium (K) are macronutrients that are important for plant growth.Phosphorus is one of the essential nutrients needed for good growth and production for oil palm plants.Lack of phosphorus in plants will slow down the process of root growth, dark and erect leaves then turn purplish and harvest time will be slow [35].
Oil palm plants during their growth phase require relatively less phosphorus than nitrogen and potassium elements.As a source of P fertilizer can be given in the form of TSP or natural-phosphate.TSP fertilizer is fast soluble with a fairly high P2O5 content of 46%, while natural phosphate has a varying P2O5 content of up to 35% more.TSP fertilizer is relatively expensive compared to natural P but dissolves faster so it is more readily available to plants, while natural P fertilizer has a large variationin total P2O5 content and availability to plants even though it is from the same deposit source [36].The use of natural P for plantations has an advantage because the price is relatively cheaper, besides that natural P has a relatively higher content of other elements (Ca, Cu and Zn).Thus, natural P-fertilizer other than as a source of P also has benefits as an ingredient to improve the physical and chemical properties of the soil [37].
The results of the study using phosphorus fertilizers on three-year-old oil palm plants could increase the length of the midrib, the circumference of the stem, and the levels of P nutrients in the leaves.The optimum dose of phosphorus fertilization based on midrib length and stem circumference was 464 g P2O5 per plant per semester [38].

Kalium fertilizer for oil palm
Potassium chloride (KCl) is a type of potassium fertilizer, with a nutrient content of 60% K2O.Giving potassium to the soil can increase the amount of available potassium, potassium is important in spurring growth and facilitating photosynthesis.The main function of potassium (K) is to help the formation of protein and carbohydrates [39].Oil palm plants require quite a lot of potassium fertilizer.The need for potassium fertilizer for oil palm can reach 2.25 kg/plant/year.Potassium fertilizer plays an important role in influencing the number, size of bunches and increasing oil palm production [40].
One of the nutrient needs that can act as an effort to increase the ability of plants when experiencing water shortages is potassium (KCl), because element K is an essential nutrient that is useful as a determinant of plant growth and is also involved in physiological processes, maintaining turgor pressure, regulates stomata opening and water potential in the plant body.Elemental K has an effect on increasing plant resistance when water needs are not available enough, plants that have sufficient element K in drought stress conditions will show the ability to process stomatal conductance, because stomata openings become smaller [39,41,42].

Pro and cons of the use of chemical fertilizer
Given that Indonesia is the world's largest producer and exporter of crude palm oil (CPO), palm oil cultivation needs to receive great attention.Palm oil has various benefits such as cooking oil bases, the main ingredients of the soap industry, cosmetics, and food.CPO is also present as an alternative fuel for biodiesel amid the depletion of world oil reserves.In the midst of the world's need for processed palm oil products, Indonesia is certainly trying to meet it by increasing the production and quality of palm oil.The improvement starts from the process of planting and maintaining plants.Therefore, every element in the process needs to be considered correctly.With proper planting and maintenance, oil palm crops can grow to the maximum and provide abundant profits for producers [2].
In the process of oil palm cultivation, the use of fertilizers is a crucial factor.There are many things that must be considered in applying fertilizer to oil palm plants, ranging from the dosage, type, to the material contained in the fertilizer.Even though we use premium quality fertilizer, we still can't be careless in using it.Because, we also need to consider aspects of fertility, soil conditions, plant growth, plant productivity, and the variety of plants used.Different varieties and soil conditions will also differ in fertilizer needs for these plants.
The use of fertilizer generally has a correlation with pollution from residues of fertilizer both in soil and water.The fertilizer consumption per hectare in Indonesia 's agricultural land including oil palm plantations is still relatively low.Data of FAO [43] showed that the used of input and soil and water among palm oil soybean oil and rapeseed oil for every ton of vegetable oil, is soybean oil used the highest amount of NPK fertilizer, pesticides and fossil energy, and in the second is rapeseed oil.As a results, pollution from the residues of fertilizer and pesticides in soil and water is also higher in plantations producing soybean oil and rapeseed oil.
Several research results indicate that most of the intensive agricultural land has experienced degradation and decreased land productivity, especially related to the very low C-organic content in the soil, which is <2%, even in many intensive rice fields in Java the content is <1%.In fact, to obtain optimal productivity, more than 2% C-organic is needed.On the other hand, Indonesia as a wet tropical country which has abundant sources of organic materials and fertilizers has not been used optimally.Organic materials or fertilizers are very useful for increasing agricultural productivity both in terms of quality and quantity, conserving nutrients, reducing environmental pollution, and improving land quality in a sustainable manner [44].

Fertilizer policy
Fertilizer is one of the important and strategic elements for increasing production and productivity, and become an integral part of farming systems.So important and strategic role of fertilizers in increasing crop production and productivity, the government continues to encourage the efficient use of fertilizers through fertilizer price policy, procurement and distribution.Along with the development, production of fertilizers, particularly chemical fertilizers continue to decline, so that in some areas there is a shortage.
Fertilizer subsidies have increased significantly since the beginning of the decade.In 2016, fertilizer subsidies amounted to Rp 30.1 trillion (US$2.27billion), a 25 percent increase over 2014.Most of the fertilizer subsidy in Indonesia dedicated mostly for food crops.However, the results of The World Bank [45] presented that 40% largest farmers capture up to 60% of subsidy.Even though 42 % oil palmhave been produced by smallholders, but no fertilizer subsidy allocated to oil palm smallholder farmer.The fertilizer subsidies contribute to an increased use of urea.The regressive nature of the fertilizer subsidies shows larger farms using a larger volume of fertilizer.Fertilizer used in adequate quantities has a positive and significant impact on rice yields, and also oil palm production, but it also provides evidence that over using fertilizer has an adverse impact on yields, an inverted U-curve relationship.Based in lessons earned from input subsidy programs we need to have clear identification and definition of program objectives.Objectives should be clear, with no room for different interpretations; targets need to be established that allow their respective budgetary allocations to be set for short-and long-term plans.Setting the program within an agriculture development strategy.An inputsubsidy program is just one of several mechanisms that work together to promote agriculture productivity.When other links are missing, the subsidies alone may not do the trick because the marketfailures they attempt to correct havemulti-dimensional causes.Thus, they require a multi-dimensional approach.The program design needs to take into account who are the target beneficiaries, what identification criteria to use, and the mechanism for the delivery of benefits, in order to minimize leakage.By improving coordination and linking the program with existing safety net initiatives, deliverycosts were reduced.Risks Accounting.Input subsidy programs are prone to high risks and these costs should be accounted for and quantified.There are many factors that contribute to risk, such as: fiscal instability, fraud and corruption, leakage, and uncertainty from external shocks (poor weather conditionsor international pricechanges).

Policy implication
To realize food self-sufficiency in Indonesia, it needs to be supported by effective of subsidized fertilizer.The main causes of ineffective of subsidized fertilizers are irregularities, weak oversight from implementing institutions and weak community control.Likewise, the aspects of transparency and information disclosure in the chain of subsidized fertilizer implementation are also still weak.So far, the regulations governing the mechanism for implementing subsidized fertilizer policies are quite adequate but their implementation is still weak.
Indonesian agriculture sector would be better served if a considerable amount of resources are reallocated.The GoI could improve the provision of public services for agriculture by investing in other agriculture public goods, which yield higher returns, while keeping two specific objectives in mind: increasing the productivity of the agriculture sector, and increasing the welfare of farmers.There is an array of options for using newly freed resources, as fertilizer is just one of many determinants of yields and agriculture productivity that complement, but do not substitute, investments in: irrigation, extension services, improved agriculture marketing (particularly in the outer islands off-Java) and research and development in agriculture.
There may be a rationale for subsidizing the purchase of agriculture inputs by small farmers who may be credit-constrained, in light of the MoA's goal to improve farmers' welfare.However, fertilizer subsidies are only one of many options to do so and they may not be the most cost-effective instrument.A more cost-effective alternative to support small farmers and overcome potential credit-market constraints would be to establish a system of cash transfers, an area in which Indonesia already has extensive experience.With awell-targeted system of cash transfers for agriculture, farmers would be in a better position to determine the level and combination of inputs best suited to their needs.

Conclusion
The demand of palm oil for domestic and international market will continue to increased and Indonesia as the largest palm oil producing country will continue to fulfill the demand in sustainable way.Most of the oil palm plantations are grown on soils that are acidic and have low fertility levels soils therefore 1243 (2023) 012020 IOP Publishing doi:10.1088/1755-1315/1243/1/01202010 fertilization will continue to be a part of the production system.Palm oil fertilization aims to add nutrients that are lacking or not available in the soil, these nutrients are needed by plants for vegetative and generative growth in order to obtain optimal fresh fruit bunches.
The use of anorganic fertilizer in palm oil still needed and as palm oil makes relatively low use of fertilizers, pesticides and fossil energy so the pollution from the residues of fertilizers and pesticides in soil and water in oil palm plantation.However since Indonesia also rich in organic materials, it is very in time that Indonesia to strengthen the use organic materials or fertilizers for increasing agricultural productivity both in terms of quality and quantity, conserving nutrients, reducing environmental pollution, and improving land quality in a sustainable manner.Furthermore, considering of 42 % palm oil produced by small holders it is suggested that the Government of Indonesia facilitating them with fertilizer subsidy.

Table 3 .
[31]ical and chemical characteristics of soil on potential acid sulfate soil and actual acid sulfate soil on top layer (0-50 cm)[31]