Abstract: Background and Objective: The problem of fertilization in Indonesia is indeed complex, especially on palm oil seedling. This study aimed to observe the effect of NPK treatment and frequency of watering to growth and proline of palm oil seedlings in pre-nursery. Materials and Methods: The experiment was done in June-September 2019. This experiment uses the RCBD Factorial method consisting of 2 treatment factors: NPK consists of 3 levels, namely, N1 = 5.0 g planting per media, N2 = 10.0 g planting per media, N3 = 15.0 g planting per media, Frequency of watering consisting of 4 levels namely L0 = 200 mL water planting per media day–1, L1 = 200 mL water planting per media days–3, L2 = 200 mL water planting per media days–5, L3 = 200 mL water planting per media days–7. The observation variables which reflect plant growth namely plant height, stem diameter, number of leaves, leaf area and one of the characteristics lack of water namely leaf proline. Results: Fertilizer NPK up to 15 g planting per media has a trend increase plant growth of palm oil seedlings in pre-nursery, frequency of watering significantly decreases plant growth, on treatment 200 mL water planting per media days–7 increases the proline content about 3.26 mM g–1. The combination of NPK fertilizer and frequency of watering has no significant effect. Conclusion: Hence it was concluded that NPK has no significant effect to the growth of seedlings, the frequency of watering which is rarely caused the growth of seedling decreased but the proline content increased in leaves.
INTRODUCTION
NPK fertilizers are so important to investigate because lately there are a lot of NPK fertilizers on the market and generally the legal group received a recommendation from the government of the Republic of Indonesia because NPK nutrients are very essential for palm oil seedlings1, smallholder plantations rarely know to provide NPK fertilizer is more suitable so that until now, seedling growth in pre nurseries is not optimal. Through this research, there is a results of NPK fertilization are needed, especially for small holders and the negative impact due to the lack of watering will enrich scientific information as an important basis for policy making2,3.
Recent progress in general understanding reveals that good seedling will produce high yield on palm oil, and one of the determinants of oil palm plant productivity is to use quality seedling and good agricultural practices, especially proper watering and NPK fertilization every 2 weeks so that the total dose required each seedling up to 8 months old is 158 g with optimal provision of water (personal communication). The NPK as a compound fertilizer is the choice of farmers because it is more efficient and cheap, while the price of other compound fertilizers such as NPK mg and Rock Phosphate is quite expensive and relatively difficult to obtain by Indonesian farmers (personal communication). Therefore, an alternative source of fertilizer that is more affordable and easy to obtain is needed, one of which is compound fertilizer NPK 15-15-15. Apart from fertilizing, watering needs to be given in the pre-nursery. Water is the most important requirement for oil palm plants in their physiological processes. Watering that is not perfect will cause abnormalities and can even lead to death of the oil palm seedlings in the pre-nursery1-4.
Previous studied was reported the influence of Vedagro fertilizer for palm oil seedlings which have composition N = 11-12%, P2O5 = 0.4-0.6%, K2O = 4.5-6.0%, Ca = 1.1% and Mg = 1.9-2.2%, enriched with iron, manganese, cuprum, zinc, boron and molybdenum and aspartic acid, glutamic acid, alanine, valine, isoleucine, leucine, tyrosine, lysine and arginine is able significantly to increase plant height of oil palm seedlings in the pre nursery1. From the results of previous studies it was observed that in the second year of immature palm oil plantations, it was revealed that compound fertilizer N, P, K significantly affected plant height, trunk girth, leaf area, NAR, Chlorophyll, nutrient N, P, K in leaf content2. Imperfect watering will cause abnormalities and can even lead to death for oil palm seedlings in the pre-nursery, even though the seeds used are superior4. Due to the desire for big profits, Smallholder oil palm plantations in Indonesia continue to expand without technical assistances and agricultural inputs especially for seedling oil palm cultivation3,4 and The problem of smallholder plantations in Indonesia is indeed complicated, from upstream to downstream. This is what makes smallholder plantations income per unit area much lower than that of those managed by the foreign private sector or state plantations.
Drought is a significant obstacle for palm oil plantations in many areas dependent on rainfall including in Indonesia. Besides, Indonesia must overcome its own problems, one of which has not been separated harvesting of palm oil from various superior varieties5. To answer this, it is not possible to have a onetime research, still it must be repeatedly started information from the morphological and physiological aspect in nurseries, one of which is at various levels of lack of watering. Palm oil of Tenera-Simalungun variety is a superior variety produced in North Sumatra and planted in multiple agro climate in Indonesia1,2. Indonesia has many areas for palm oil plantations with low rainfall, moderate and high rainfall, finally, the correlation of this research will be to low rainfall. In this case, morphological and physiological characterizations need to be prior to molecular markers. The characteristic of this fertilizer is that it dissolves easily and reacts quickly so that plants rapidly absorb it. The need for water for palm oil seedlings in the pre-nursery is 200 mL planting per media day–1, below 200 mL planting per media day–1 is considered to be lack of watering6-9.
This study determined the optimal dose of NPK fertilizer for palm oil seedlings in the pre-nursery and frequency of watering whether the results are the same watering every day with watering once every three days or once 5 days or once a week to get better seedling. This will advance new knowledge, mainly from the agronomic aspect, namely what the NPK relationship is like and the frequency of water application on the growth and proline content of oil palm seedlings.
MATERIALS AND METHODS
Study area: This research uses Tenera of variety of Simalungun, from PPKS (The Indonesia Palm oil Research Institute), experiment was carried out in a plastic house to see some morphological growth and leaf proline content.
Methodology: The experiment was done in June-September, 2019. This research uses the RCBD Factorial method consisting of 2 treatment factors. The first factor of NPK Fertilizer Dose consists of 3 levels, namely, N1 = 5.0 g planting per media, N2 = 10.0 g planting per media, N3 = 15.0 g planting per media, while the second factor is lack of watering consisting of 4 levels namely L0 = 200 mL water planting per media days–1 (control), L1 = 200 mL water planting per media days–3, L2 = 200 mL water planting per media days–5 and L3 = 200 mL water planting per media days–7. According to applicable standards, soil weight in plant media that is baby polybag 1 kg. The observation variable was observed at ages 4-12 weeks after the plant which reflects plant growth namely plant height, stem diameter, number of leaves, leaf area and one of the characteristics when palm oil seedling lack water namely leaf proline content.
Statistical analysis: Statistical data processing using analysis of variance source, and if the effect of NPK or and lack of watering treatment is significant, followed by the LSD test at the level of p<0.05. Proline content was carried out at the Laboratory of the Institute of Research and Development of Agriculture-Center for Research and Development of Agriculture Biotechnology and Genetic Resources of Agriculture, Bogor-West Java. Data processing in statistical only at 12 Weeks after Planting (WAP).
RESULTS
Plant height: Table 1 shows a trend that the higher the dose of NPK the more increased the plant height (16.80 cm) although is not significant, the less watering the more depressed the growth of seedlings, Watering 200 mL planting per media days–7 significantly reduces plant height of palm oil seedlings highest to only 10.10 cm at ages 12 weeks after planting, meanwhile, if normally the seedling growth which is represented by plant height has far exceeded this numbers.
Figure 1 shows relationship between plant height and frequency of watering at ages 12 WAP, following the regression Eq.:
this can be interpreted in the agronomic approach that each decreased of 1 L in watering will decrease plant height 5.23 cm, with r value 0.87.
Stem diameter: The diameter of seedlings continue to increase with increasing ages (Table 2). Table 2 shows a trend that the higher the dose of NPK fertilizer the higher the stem diameter is found though is not significant, on the other hand the less watering the more depressed the stem diameter of seedlings, watering 200 mL planting per media days–7 significantly reduces stem diameter of palm oil seedlings to only 2.29 mm at ages 12 weeks after planting (Table 2).
| Table 1: Plant height of palm oil seedling due to NPK fertilizer and frequency of watering at ages 4-12 WAP | |||||
| Plant height (cm) | |||||
| Treatments NPK | 4 WAP |
6 WAP |
8 WAP |
10 WAP |
12 WAP |
| N1 | 9.13 |
10.68 |
13.30 |
14.36 |
15.54 |
| N2 | 9.85 |
11.53 |
13.32 |
14.58 |
16.61 |
| N3 | 9.49 |
11.99 |
14.99 |
15.91 |
16.80 |
| Frequency of watering | |||||
| L0 | 9.62 |
13.18 |
16.19 |
20.40 |
23.86a |
| L1 | 9.60 |
13.33 |
15.99 |
19.82 |
23.37a |
| L2 | 9.33 |
12.07 |
12.19 |
12.29 |
12.35ab |
| L3 | 9.17 |
10.02 |
10.09 |
10.99 |
10.10b |
Numbers followed by the same letter in the same column are not different from the LSD test at the 5% level, N1: 5.0 g planting per media, N2: 10.0 g planting per media, N3: 15.0 g planting per media, L0: 200 mL water planting per media day–1; L1: 200 mL water planting per media days–3, L2: 200 mL water planting per media days–5, L3: 200 mL water planting per media days–7 , WAP: Weeks after planting |
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| Table 2: Stem diameter of palm oil seedling plant due to NPK fertilizer and frequency of watering at ages 4-12 WAP | |||||
| Stem diameter (mm) | |||||
| Treatments NPK | 4 WAP |
6 WAP |
8 WAP |
10 WAP |
12 WAP |
| N1 | 3.15 |
4.35 |
4.48 |
4.82 |
5.42 |
| N2 | 3.18 |
4.39 |
4.52 |
5.16 |
5.64 |
| N3 | 3.32 |
4.43 |
4.78 |
5.35 |
5.76 |
| Frequency of watering | |||||
| L0 | 3.19 |
4.38 |
4.85 |
5.24 |
6.10a |
| L1 | 3.16 |
4.25 |
4.81 |
5.19 |
5.81a |
| L2 | 3.13 |
4.14 |
4.34 |
4.42 |
4.46ab |
| L3 | 2.10 |
2.14 |
2.19 |
2.26 |
2.29b |
Numbers followed by the same letter in the same column are not different from the LSD test at the 5% level, N1: 5.0 g planting per media, N2: 10.0 g planting per media, N3: 15.0 g planting per media,L0: 200 mL water planting per media day–1; L1: 200 mL water planting per media days–3, L2: 200 mL water planting per media days–5, L3: 200 mL water planting per media days–7 , WAP: Weeks after planting |
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| Table 3: Number of leaves of palm oil seedling plant due to NPK fertilizer and frequency of watering at ages 4-12 WAP | |||||
| Number of leaves (leaf) | |||||
| Treatments NPK | 4 WAP |
6 WAP |
8 WAP |
10 WAP |
12 WAP |
| N1 | 2.61 |
3.52 |
4.49 |
5.57 |
5.6 |
| N2 | 2.64 |
3.57 |
4.52 |
5.68 |
6.19 |
| N3 | 2.67 |
3.63 |
4.66 |
5.78 |
6.2 |
| Frequency of watering | |||||
| L0 | 2.67 |
3.65 |
4.67 |
5.87 |
6.50a |
| L1 | 2.65 |
3.11 |
3.67 |
5.61 |
6.42a |
| L2 | 2.65 |
3.01 |
3.41 |
3.82 |
4.11ab |
| L3 | 2.56 |
2.64 |
3.19 |
3.25 |
3.26b |
N1: 5.0 g planting per media, N2: 10.0 g planting per media, N3: 15.0 g planting per media,L0: 200 mL water planting per media day–1; L1: 200 mL water planting per media days–3, L2: 200 mL water planting per media days–5, L3: 200 mL water planting per media days–7, WAP: Weeks after planting |
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| Table 4: Leaf area palm oil seedling due to NPK fertilizer and frequency of watering treatment at ages 12 Weeks After Planting (WAP) | |||||
| Frequency of watering | |||||
| Treatments NPK | L0 |
L1 |
L2 |
L3 |
Average |
| N1 | 32.11 |
27.24 |
18.27 |
12.12 |
22.43 |
| N2 | 32.27 |
27.16 |
18.13 |
12.11 |
22.41 |
| N3 | 32.87 |
26.50 |
17.80 |
11.32 |
22.12 |
| Average | 32.41a |
26.96ab |
18.06ab |
11.85b |
- |
Numbers followed by the same letter in the same row are not different significant from the LSD test at the 5% level, N1: 5.0 g planting per media, N2: 10.0 g planting per media, N3: 15.0 g planting per media |
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| Fig. 1: | Relationship between plant height and frequency of watering at ages 12 WAP |
| Fig. 2: | Relationship between stem diameter and frequency of watering at ages 12 WAP |
Figure 2 shows relationship between stem diameter and frequency of watering at ages 12 WAP, following the regression Eq.:
this can be interpreted in the agronomic approach that each decreased of 1 L in watering will decrease stem diameter 1.27 mm, with r value 0.90.
Number of leaves: Number of leaves continues to increase with increasing ages (Table 3), effect of NPK fertilizer is not significant. The effect of frequency of watering is significant on the number of leaves, for more details can be seen in Fig. 3, relationship between number of leaves with frequency of watering at ages 12 WAP following the regression Eq.:
Leaf area: Due to NPK fertilizer and frequency of watering treatment at ages 12 weeks after planting (WAP) on Table 4. Effect of NPK fertilizer is not significant while watering 200 mL planting per media days–7 significantly reduces leaf area of palm oil seedlings to only 11.85 cm2 at 12 weeks after planting, with the regression equation as in Fig. 4.
| Table 5: Experiment matrix at age of 12 WAP with frequency of watering | |||||
| Treatments | Plant height (cm) |
Stem diameter (mm) |
Number of leaves (leaf) |
Leaf area (cm2) |
Proline (mM g–1) |
| L0 | 23.86a |
6.10a |
6.50a |
32.41a |
1.65b |
| L1 | 23.37a |
5.81a |
6.42a |
26.96ab |
2.24b |
| L2 | 12.35ab |
4.46ab |
4.11ab |
18.06ab |
3.93ab |
| L3 | 10.10b |
2.29b |
3.26b |
11.85b |
4.91a |
Numbers followed by the same letter in the same column are not different from the LSD test at the 5% level, L1: 200 mL water planting per media days–3, L2: 200 mL water planting per media days–5, L3: 200 mL water planting per media days–7 , WAP: Weeks after planting |
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| Fig. 3: | Relationship between number of leaves and frequency of watering at ages 12 WAP |
| Fig. 4: | Relationship between leaf area and frequency of watering at ages 12 WAP |
From regression Eq.:
can be interpreted that each decrease of 1 L watering will decrease 7.06 cm2 leaf area.
Proline content: Proline content in Leaf area due to frequency of watering treatment at ages 12 Weeks after Planting (WAP) shown in Table 5 and Fig. 5. Watering 200 mL planting per media days–7 significantly increases proline to 4,91 mM g–1 at 12 weeks after planting.
Relationship between proline and Frequency of Watering at ages 12 WAP is shown in Fig. 5. The Fig. 5 shows relationship between proline and frequency of watering at ages 12 WAP follows regression Eq.:
means that each decrease of 1 L in watering will increase Proline in leaf 1.15 mM g–1.
DISCUSSION
The NPK only contains nutrients N, P, K, meaning this is in accordance with the theory that applying NPK fertilizer will produce optimal seedling growth but in this study the effect is not significant. Fertilizer NPK up to 15 g planting media–1 has a trend increase in plant growth of palm oil seedlings in pre-nursery, seen from plant height, stem diameter, number of leaves, leaf area. According to nursery experts that NPK fertilization every 2 weeks so that the total dose required each seedling up to 3 months old is 59.25 g with optimal provision of water, in this study, the total NPK fertilizer given is not the same with 59.25 g, maybe this is the reason why NPK fertilizer had no effect significantly. On the other hand, applying only NPK fertilizer can cause soil to become hard because it can accumulate residues in the soil. The results of the previous study show that the application of 25% NPK and 75% organic matter gave the best results such as root length, root area, leaf area, the number of leaves, plant height, and dry matter plant10,11. This conditions, presumably, palm oil form osmoprotectant to maintain the stability of cell to deficit water. This is not much different from the results of previous studies that the average dry matter yields of palm oil from all stressed environments did not differ significantly from each other but significantly lower than those that were not stressed6.
The results of the regression analysis from previous studied showed that 72% of the compost and topsoil mixture planting media determined the growth performance of palm oil seedlings in the pre-nursery phase which was supported by leaf or N, P, K supplemented with micro nutrients through the leaves12.
Application fortified organic fertilizer in the main nursery at 200 g rate can increase growth and soil fertility, it is the best alternative to replace Fertilizer NPK, which is used in nursery stage13, a combination of 50% NPK+OPEFB compost gives the best effect on the parameters of increasing the height of oil palm seedlings, stem diameter, number of leaves and dry weight of seedlings14. Other researchers found that the use of 25% NPK substituted with 75% organic material contributes to the best results in increasing the growth performance of oil palm seedlings in pre-nursery and main nursery15. In other crops, NPK fertilizer has a significant effect on plant height, number of leaves, total fruit count and total fruit weight of tomato plants16. In contrast to oil palm plants, compared with NPK fertilizer (300 kg ha–1), poultry manure is more improved the performance of tomato and its nutrient status17, moderate rates of NPK fertilizer (100 or 200 kg ha–1) can be applied to boost soya bean production18. Apart from NPK, other nutrients are often added to make the results more satisfactory, for example, NPK 2,600+25 g boric acid +25 g CuSO4.5H2O (P3) per palm oil significantly increased the growth of palm oil linearly as shown by plant height, leaf number, leaf area of frond number nine, chlorophyll content, N and P content of the leaves19.
One of the characteristics of oil palm seedling due to lack of water is the increase in leaf proline content as a form of adaptation. Furthermore, proline accumulation in the leaves of water-stressed palm oil seedlings plays an essential role in maintaining turgor, so that proline accumulation is the common response of plant to drought stress, also palm oil plantation with water scarcity significantly reduces growth and oil yield and an increase in stomatal resistance4,20, also palm oil plantation with water scarcity significantly reduces growth and oil yield20,21. This results inform the significance of water. Also, the aeration of palm oil seedlings and pore space is crucial to note12, based on lipid peroxidation, glycine betaine and proline contents, found in some drought tolerant sugarcane genotypes22. Proline is an excellent osmolyte as well as a metal chelator, an antioxidative defense molecule and a signaling molecule23. Proline accumulation is caused by the activation of proline biosynthesis and inactivation of proline degradation although it is still not fully understood24. Low temperature and lack of watering inhibited the growth of palm oil seedlings. The relative conductivity, injury index, malondialdehyde and proline content in the leaves increased to different degrees of low temperature and drought stress23,24. Also, the activity of superoxide dismutase and peroxidase also increases25, although using superabsorbent, is still increases superoxide dismutase activity when the irrigation deficit is 80% compared to full irrigation26.
Proline is the most suitable osmolytes for plants experiencing lack of watering26. Glutamate appears to be the primary precursor of proline, why elevated proline levels lead to enhanced osmotolerance are still discussed. A lot of evidence shows that a positive correlation exists between proline accumulation and plant stress tolerance27,28. Some researchers induce resistance of palm oil seedlings but have not been success as expected, for example, the optimal dose of Si to induce resistance of palm oil seedlings to drought stress has a linear trend29. One thing to remember is that proline accumulation in plants is not only in the condition of lack of watering but also as plant signaling30.
The implication of this experiment is NPK fertilization is needed, especially for smallholders and negative impact due to the lack of watering will enrich scientific information as an important basis for policy making. Watering should be according to the recommendation of 200 mL of water planting per media day–1. Limitation of this study, not yet known whether the results of this experiment in nurseries are strongly correlated when planted in different places in Indonesia include now on land that produce crude palm oil.
CONCLUSION
Fertilizer NPK up to 15 g planting per media has a trend to increase the growth of palm oil seedlings in pre-nursery. Frequency of watering that rarely or lack of watering significantly decreases plant growth seedlings of palm oil but increases proline content. Frequency of watering (200 mL water planting per media days–7) can increase the proline content 3.26 mM g–1. The combination of doses of NPK fertilizer and frequency of watering has no significant effect on all observation experiment.
SIGNIFICANCE STATEMENT
This study discovers the effect of NPK fertilizer to produce growth of palm oil seedlings and the effect of frequency of watering on seedling growth. This study will help researchers, farmers, seed industry to uncover the critical point on a nursery in various places in Indonesia, especially in NPK fertilization and frequency of watering. Thus, a new theory is found that on the frequency of watering 200 mL water planting per media days–7 can be predicted proline content formed may be arrived at.
ACKNOWLEDGMENT
We express our gratitude to the Board of Darma Agung University Foundation and Rector of Darma Agung University for their help both materially and morally. They provided fees through the competitive scheme for 2 research titles during 2019. Our first research was aimed at finding out the effect of Vedagro fertilizer.