Mycorrhizae utilization in palm oil nurseries to reduce inorganic fertilizer dose

Fertilization in palm oil nurseries is an invaluable tending activity to obtain healthy and robust seedlings. This research aims is to identify the dose percentage level of the inorganic fertilizer which can be reduced by applying mycorrhizae in oil palm nurseries. The research design used a non-factorial completely randomized design, as the treatment factor was the dose of fertilizer in oil palm nurseries. There are 5 levels of treatment, namely P0 (100% of the standard dose + 50 g mycorrhizae), P1 (75% of the standard dose + 50 g mycorrhizae), P2 (50% of the standard dose + 50 g mycorrhizae), P3 (25% of the standard dose + 50 g mycorrhizae), and P4 (0 inorganic fertilizer + 50 g Mycorrhizae). Each treatment was arranged in four replications. The data were analyzed using ANOVA, if F-count > F-table then it is continued with Duncan Multiple Range Test. The observation variables included plant height, number of leaves and stem diameter, root length, canopy dry weight, roots dry weight, and P uptake. The results showed that there were significant differences in plant height, number of leaves, stem diameter, roots dry weight, canopy dry weight and P uptake in leaves as well as, while the observations of root length showed no significant difference. The application of 50 grams of mycorrhizae with a 50-75% standard dose of fertilization resulted in optimal seedling growth. Mycorrhizae utilization can reduce the application of inorganic fertilizers up to 25-50%.


Introduction
Fertilization is a planned plant nursery activity which aims to maintain or increase soil fertility [1].Fertilization is also carried out in oil palm nurseries.During the growth process, oil palm seedlings absorb nutrients from the soil which are then processed in the leaves through the process of photosynthesis and the results are translocated to all parts of the plant.The amount of nutrients needed in the nursery phase depends on the age of the seedlings.The results of [2]'s research conducted at Tanjung Garbus Plantation, in the early nurseries (4 to 12 weeks old) required 1.2 grams of compound fertilizer 12-12-17-2 and 1.5 grams of urea per seedling, while in the main nursery (4 to 40 weeks in large polybags) required 157.5 grams of compound fertilizer 20-12-5-2, 160 grams of compound fertilizer 12-12-17-2, and 26.78 grams of urea per seedling.A large amount of fertilizer needed has implications for the cost of fertilization.
The fulfilment of plant nutrients is very dependent on the planting medium.The planting medium used in oil palm nurseries is topsoil [3].However, it is difficult now to meet the need for topsoil in massive quantities.Hence, ultisol soil, which is the type of soil that dominates Indonesia's mainland is used as a planting medium for oil palm nurseries [4].Ultisols are acidic soils due to the K, Ca, and Mg nutrients which have been leached, the fertility level of ultisols is relatively low, and the soil is yellowish 1243 (2023) 012018 IOP Publishing doi:10.1088/1755-1315/1243/1/012018 2 or reddish due to the presence of Fe oxides [5].Because ultisol is acidic and rich in aluminum, the efficiency of P fertilization on ultisol is low, namely <10% [6].Furthermore, the availability of N, K, Ca, Mg and S nutrients tends to decrease with the decreasing of pH [7].This was followed by the low fertilization efficiency as reported, the efficiency of N fertilization was only 30%, P fertilization was only 23%, and K fertilization was only 33% [7].Based on the description of the problem, an effort is needed, hence fertilization is carried out effectively and efficiently.
Arbuscular Mycorrhizal (AM) fungi are known to play an important role in the sustainability and stability of ecosystems.It is estimated that 200,000 plant species can associate with AM fungi, which contributes greatly to plant growth and production [8].AM fungal infection can increase the ability of plants to utilize nutrients, especially P, Ca, N, Cu, Mn, K and Mg.Mycorrhizal roots have a greater energy metabolism hence they are active in P uptake at a concentration of 10-7-10-6 in the soil solution to become 10-3-10-2 in plant roots.In addition to their ability to absorb nutrients at low concentrations, AM fungi also play a role in increasing the ability of plants to absorb water and protect plant roots from pathogen attacks [9].
Currently, AM fungi have been produced commercially and are available in large and small packages hence consumers can easily obtain AM fungi to apply as fertilizer for their cultivated plants.AM fungi have been introduced for a long time, but there are still few oil palm plantation business actors who use AM fungi.On the other hand, the role and benefits of AM fungi are known in increasing the availability of nutrients.The type and dose of fertilizing oil palm seeds using topsoil as a planting medium are also widely known.However, data on the growth of oil palm seedlings and the percentage of the fertilizer dose can be reduced with the type and dose coupled with the application of mycorrhizae on ultisol as a planting medium has not been obtained.Therefore, this research aims to determine the growth of oil palm seedlings and the percentage of inorganic fertilizers that can be reduced in the oil palm main nursery by AM (MycoVir) fungi application.

Method 2.1 Research design
This research used a non-factorial completely randomized design, as a treatment factor, namely the dose of fertilization in the main nursery with the addition of 50 g mycorrhizae.The treatment arrangement was P0 (100% standard dose of fertilization + 50 g Mycorrhizae), P1 (75% standard dose of fertilization + 50 g Mycorrhizae), P2 (50% standard dose of fertilization + 50 g Mycorrhizae), P3 (25% standard dose of fertilization + 50 g Mycorrhizae), and P4 (Without inorganic fertilizers + 50 g Mycorrhizae).Each treatment was repeated 4 times, each unit contained 2 seeds, the number of samples was 40 units.The results of observations are compiled in a list of variances and then analysed using Analysis of Variance (ANOVA), if there is a significant difference, then proceed with Duncan's Multiple Range Testat the 5% level.

Tools and materials
The materials used in this research were ultisol as a planting medium, water for watering plants, 3 months old DxP Dumpy PPKS variety, compound fertilizer 15.15.6.4,compound fertilizer 12.12.7.2, kieserite fertilizer, arbuscular mycorrhizae cultured in sterile sand and vermiculite (MycoVir), polybagsize 40 cm x 50 cm.The tools used are a meter, a watering can, a soil sieve, a hoe, a cutter knife, clear plastic, a measuring cup, a test tube, scales, an oven and a spectrophotometer.

Research implementation
Planting Seeds: The 3-month-old seedlings from Pre-Nursery were planted in a 40 cm x 50 cm Main Nursery polybag which already contained 8 kg of ultisol.Seedlings were watered regularly, 2 times a day, each 1 litre in the morning and 1 litre in the afternoon.
Fertilization of oil palm seedlings applied begins in the 2nd week after transplanting.The dose of inorganic fertilizer used in this research refers to the main nursery fertilization dose.Types and doses of fertilizers based on treatment are presented in Table 1.

Observation
In this research, several observations were made, namely laboratory tests on soil properties used as planting media, observations on oil palm seedling growth, and P nutrient uptake.The observations are described as follows: x The characteristics of soil: the planting medium used is ultisol.Soil is analyzed in the laboratoryto identify the chemical properties and soil texture.The results of soil analysis are listed in Table2, which shows that the soil contains very low C-organic content.Furthermore, N, P, and K levels are included in low criteria, and so is the pH level (acid).Meanwhile, the soil texture is sandy clay loam.x Plant height: Plant height was measured from the base of the stem to the tip of the leaf that has expanded.The leaves were erected and then measured with a meter.The measurements were made every 2 weeks for 20 weeks of the research period.
x The number of leaves: The leaves that are counted are leaves that have fully opened.
x The diameter of the rod is measured using a cloth tape measure.Then the diameter is calculatedusing the circumference of a circle formula (diameter = rod circumference:π).x Root length: Seedlings are dismantled in advance, and the soil adhering to the roots is rinsed with water.The measurement of the oil palm root length was carried out from the base of the stem which was marked with a marker to the tip of the root of the seedling using a tape measure.
x The roots and shoots dry weight: The roots and shoots that have been rinsed with water and thenairdried were weighed to obtain the wet weight.Furthermore, the roots and shoots were put inthe oven at 70 o C for 24 hours to obtain the dry weight.x P uptake: P uptake is the P nutrient content in leaves multiple by the plant dry weight.P nutrient content was analyzed using the Dry Ashing Method.

Plant height, number of leaves and stem diameter
The results of the statistical test of plant height presented that the average plant height was not significantly different at the age of 4, 5, and 7 months.But it was significantly different at the age of 6 and 8 months with the application of inorganic fertilizer treatment based on fertilization standards for oil palm seedlings in the main nursery and accompanied by the application of 50 g mycorrhizae.The applications of 50% and 75% of the standard dose + 50 g mycorrhizae at 8 months old were the best plant heights compared to other treatments.The lowest plant height was identified in the treatment of 0 g inorganic fertilizer + 50 g mycorrhizae, which was 42.6 cm.The treatment of 0 g inorganic fertilizer + 50 g mycorrhizae presented slower seedling growth when compared to the standard for oil palm seedling growth based on the Indonesian Oil Palm Research Institute (IOPRI), the 8-month-old seedling height should be 64.3 cm but in the treatment of 0 g inorganic fertilizer + 50 g mycorrhizae, the seedling height is 51 cm or equivalent to 7 months old of a seedling.
The number of leaves of oil palm seedlings at the age of 4 to 6 months presented no significant difference but presented a significant difference at the age of 7 and 8 months in the fertilization treatment with different doses and 50 g of mycorrhizae.The application of 75% of the standard dose + 50 g mycorrhizae produced the most leaves, namely 13.8 leaves and the lowest was identified in the treatment without the application of inorganic fertilizers + 50 g mycorrhizae, which was 11.0 leaves.The observation of stem diameter presented a significant difference between treatments on 8month-old seedlings, application of 50% of the standard dose + 50 g mycorrhizae resulted in the largest stem diameter of 5.4 cm while the smallest stem diameter was identified in the treatment of 0 g inorganic fertilizer + 50 g mycorrhizae which was 3.3 cm.

Figure 3. Stem diameter of oil palm seedlings at the age of 4 to 8 months
Plant height, number of leaves and stem diameter at seedling age of fewer than 6 months did not present significant differences, this indicates that it takes approximately two months for adaptation and development of mycorrhizae in root tissue hence it shows significant results.Overall, the results presented that although the dose of inorganic fertilizer was applied 100% according to the recommended dose for oil palm nurseries, the plant height, number of leaves and stem diameter of seedlings were lower than those treated with reduced doses of inorganic fertilizers.This confirms that mycorrhizae willfunction optimally on marginal and nutrient-poor soils [10].The effect of AM fungal inoculation on plant growth, P uptake and crop yields were also influenced by plant types and varieties, soil types, fertilizer types and other environmental factors.

Root dry weight, root length, shoot dry weight and P uptake
Fertilization with different doses and the application of 50 g mycorrhizae presented significantly different results between treatments, the treatment of 100% standard fertilizer dose + 50 g mycorrhizae was not significantly different from the treatment of 25% standard fertilizer dose + 50 g mycorrhizae, but significantly different with the treatment of 50% standard fertilizer dose and 75% standard fertilizer dose plus 50 g of mycorrhizae.In the treatment of 100% standard fertilizer dose + 50 g mycorrhizae, the highest root dry weight was obtained at 112.65 g.On the other hand, the lowest root dry weight was identified in the treatment of 0 g inorganic fertilizer + 50 g mycorrhizae.Root length was not significantly different between treatments, root length for all treatments ranged from 53.5 cm to 64.75 cm, this is presented in Figure 4, which forms a sloping line.Plant roots are indicators of plant growth that can be seen clearly and are closely related to the presence of nutrients, toxic elements, water, and pathogens in the soil.The shoot dry weight was significantly different between treatments, the dry weight presented the actual biomass, and the size of the biomass produced was a reflection of the plant's ability to absorb nutrients during the growth period.In this case, treatment of 75% and 50% standard fertilizerdose + 50 g mycorrhizae presented the highest canopy dry weight compared to other treatments.The lowest canopy dry weight was identified in the treatment of 0 g inorganic fertilizer + 50 g mycorrhizae, and this was identified in each parameter of the observation.
P uptake presented significant differences between treatments, treatment of 75% standard fertilizer dose + 50 g mycorrhizae and 50% standard fertilizer dose + 50 g mycorrhizae presented no significant difference in P uptake in oil palm seedlings.P uptake in the treatment ranged from 40.55% and 37.13%, respectively.The lowest nutrient uptake was identified in the treatment of 0% inorganic fertilizer + 50 g mycorrhizae.These results indicate that sufficient nutrients are needed for optimal growth.Ultisols are acidic soils, hence the tendency for ultisols is the binding of P nutrients by Al and Fe [7].Oil palm seedlings inoculated with mycorrhizae and application of 50% fertilizer from the standard dose have achieved optimal growth of oil palm seedlings even surpassing the growth of oil palm seedlings based on IOPRI (8 months old seedlings have 11.5 leaves, 64.3 cm high seedlings and 3.6 cm stem diameter).The AM fungi inoculation changed the morphology and root architecture of oilpalm seedlings for the better [11].

Conclusion
The growth of oil palm seedlings on ultisol planting media with the application of 50% to 75% of the standard fertilization dose coupled with the application of 50 g of mycorrhizae resulted in optimal Roots dry weight, roots lenght, canopy dry weight, P uptake

Figure 1 .
Figure 1.The average height of oil palm seedlings at the age of 4 to 8 months

5 Figure 2 .
Figure 2. Number of leaves of oil palm seedlings at the age of 4 to 8 months of the standard dose + 50 g mycorrhizae) P1 (75% of the standard dose + 50 g mycorrhizae) P2 (50% of the standard dose + 50 g mycorrhizae) P3 (25% of the standard dose + 50 g mycorrhizae)

Figure 4 .
Figure 4. Roots dry weight, roots length, canopy dry weight, P uptake of the standard dose + 50 g standard dose + 50 g standard dose + 50 g standard dose + 50 g fertilizer +

Table 1 .
Type and dose of fertilizer applied

Table 2 .
The soil characteristics analysis results