Key findings:

The study found that applying 100 ml of lamtoro leaf liquid organic fertilizer six times resulted in the best growth for siomak plants (Lactuca sativa L.). This treatment significantly improved plant health, demonstrating that lamtoro leaf fertilizer is an effective alternative to inorganic fertilizers for enhancing crop production.

What is known and what is new?

Lamtoro leaf liquid organic fertilizer, rich in nitrogen, is beneficial for plant vegetative development. This study identifies the optimal dose (100 ml) and frequency (six times) of lamtoro leaf liquid fertilizer application for improving the growth of siomak plants (Lactuca sativa L.).

What is the implication, and what should change now?

The study demonstrates that lamtoro leaf liquid organic fertilizer can effectively enhance the growth of siomak plants, providing a sustainable alternative to inorganic fertilizers. Farmers and growers should adopt the optimal application of 100 ml per plant, applied six times, to improve crop yield and reduce reliance on inorganic fertilizers.

Siomak (Lactuca sativa L.) has a characteristic fragrant aroma like pandan and has a crunchy texture when eaten raw. Efforts to increase the healthy siomak lettuce variety in the sense that it is free from pesticides, can be done by cultivating the lettuce with an organic farming system. 

Organic farming emphasizes fertilization, utilization of soil biological strength, and water use and plant management in an organic and structured way to encourage the growth and production of horticultural crops. Organic products can be used for improvement in the future, both for domestic and foreign markets.

Lack of plant nutrition is a limiting factor in increasing crop production. The main nutrient needed by plants is fertilizer. Lamtoro leaf liquid organic fertilizer can be used as an alternative to reduce the use of inorganic fertilizers.

Lamtoro leaves are an alternative raw material because they contain high nitrogen elements which are good for supporting plant vegetative development. Roidi (2016) [1], stated that the content of macro elements found in lamtoro leaves is 3.84% Nitrogen; 2.06% Potassium; 1.31% Calcium; 0.33% Magnesium 0.51% SO4 and 0.22% Phosphorus. The content of micro nutrients consists of 15 ppm Cu, 191 ppm Mn, 171 ppm Fe, and 33 ppm Zn. Septirosya et al (2019) [2], the application of lamtoro leaf POC to tomato plants with a concentration of 10% can increase the height of tomato plants by up to 0.96% compared to a concentration of 30%.

The use of fertilizers must pay attention to the time, method of fertilization and the appropriate dose. Therefore, it is necessary to conduct research on " Siomak Plant Response ( Lactuca satifa L. ) to various Doses and Frequency of Lamtoro Leaf Liquid Organic Fertilizer".

The research was conducted from 16 September 2022 to 14 November 2022 in the yard, RT 1, RW 1, Jegong Hamlet, Wilangan Village, Wilangan District, Nganjuk Regency.

This study used tools, namely poly bags measuring 30x30 cm, measuring cups, screw cups, plastic plates, calipers, labels, rulers and cellphone cameras, analytical scales, 150 L barrels and modified mori cloth such as tea bags. The materials prepared in this study used lettuce seeds of the siomak variety with the trademark known-you seed. The planting medium uses soil, husk charcoal, and cow manure in a ratio (1:1:1). 20 liters of leri water, 5 kg of shaved lamtoro leaves, 1000 ml of EM4 and 500 ml of molasses.

The implementation of this research is the manufacture of liquid organic fertilizer, preparation of seeds and nurseries, planting, maintenance and harvesting.

This study used a two-factor factorial Completely Randomized Design (CRD) and was repeated 3 times. The first factor was the dose of lamtoro leaf liquid organic fertilizer which consisted of 4 treatment levels, namely D0: 1.3 g/urea plant, D1: 50 ml/Lamtoro leaf POC plant, D2: 75 ml/Lamtoro leaf POC plant, D3: 100 ml/Lamtoro leaf POC plant. The second factor was the frequency of giving lamtoro leaf liquid organic fertilizer which consisted of 3 treatment levels, namely F1 : 4 times, F2 : 5 times, F3 : 6 times. The results of the combination of the two factors obtained 12 treatment combinations and were repeated 3 times so that there were 36 experimental units. Parameters observed included plant length, number of leaves, fresh weight of plants, leaf area, number of marketable leaves and chlorophyll and NPK POC content tests. Processing the data using analysis of variance based on a Completely Randomized Design followed by a 5% BNJ Test.

2.1 Results

2.1.1. Plant Length

At the age of 21 DAP, the highest average plant length was in the combination of 50 ml POC with a frequency of 4 times administration, but at the age of 60 DAP, the highest average plant length was in the combination treatment dose of 100 ml POC/plant with a frequency of 5 times administration. The average length of siomak plants at the ages of 28, 35, and 42 HST, treatment with 1.3 grams of urea/plant 4 times showed the highest growth. The highest average yield of siomak plant length was at the age of 56 and 60 HST (Table 1.), namely in the combination treatment of 100 ml lamtoro leaf liquid organic fertilizer (POC) and the frequency of fertilizer application 5 times. The treatment was not significantly different from the combination treatment of liquid organic fertilizer (POC) doses of 75 ml of lamtoro leaves and the frequency of 4 times and 6 times of lamtoro leaf organic fertilizer, not significantly different from the control treatment using urea with a frequency of 6 times of fertilizer application.

Table 1. Average Siomak Plant Length in Combination Treatment of Lamtoro Leaf Liquid Organic Fertilizer (POC) Dosage and Frequency of Lamtoro Leaf Organic Fertilizer Application Age 21, 28, 35, 42, 49, 56 and 60 DAP.

Note: Numbers followed by the same letter for each age

1. Number of Leaves

At the age of 49 HST, the highest average number of siomak leaves was seen in the combination treatment dose of 100 ml/plant with a frequency of 6 times, namely 14 leaves and yielded 27.3% more than the control treatment of 1.3 grams of urea given 6 times. The lowest average number of leaves aged 49, 56, and 60 DAP was seen in the D1F1 treatment combination, namely 50 ml POC 4 times. So that the combination treatment of liquid organic fertilizer (POC) doses of 100 ml of lamtoro leaves and the frequency of giving 6 times of organic fertilizer of lamtoro leaves is the most efficient combination treatment to increase the number of plants.

Table 2. Average Number of Siomak Plant Leaves in the Combination Treatment of Lamtoro Leaf Liquid Organic Fertilizer (POC) and Frequency of Lamtoro Leaf Organic Fertilizer Application Age 49, 56 and 60 HST.

Note: The numbers followed by the same letter at each age of observation are not significantly different based on the 5% BNJ test.

1. Plant Wet Weight

The results of the average wet weight of siomak plants as a result of the combination treatment of lamtoro leaf POC doses and the frequency of lamtoro leaf organic fertilizer, showed a very significant difference.

The average yield of the heaviest wet weight of siomak plants was in the combination treatment of 100 ml lamtoro leaf POC dose with 6 times the frequency of giving lamtoro leaf organic fertilizer of 83.67 grams. When compared with the control treatment D0F3, which was a combination of 1.3 grams of urea given 6 times, the D3F6 combination gave a 29.4% higher yield.

The combination treatment that produced the lightest average wet weight of siomak plants was the combination treatment of 50 ml lamtoro leaf liquid organic fertilizer (POC) with 5 times the frequency of lamtoro leaf organic fertilizer but not significantly different from the 50 ml liquid organic fertilizer (POC) dose combination treatment with 4 times lamtoro leaf organic fertilizer and not significantly different from the control treatment with 3 times lamtoro leaf organic fertilizer.

The combination that can increase the average wet weight of siomak plants (Table 3.) is the combination treatment of 100 ml lamtoro leaf liquid organic fertilizer (POC) with a frequency of 6 times lamtoro leaf organic fertilizer. 

Table 3. Average Wet Weight of Siomak Plants in the Combination Treatment of lamtoro leaf POC doses and the frequency of lamtoro leaf organic fertilizer application

Note: Numbers followed by the same letter in the same column and rows are not significantly different based on the 5% BNJ test.

1. Number of Leaves Worth Selling

The average yield of the number of salable leaves on siomak plants (Table 4.8) as a result of the combination treatment of lamtoro leaf POC doses and the frequency of lamtoro leaf organic fertilizer, shows a very significant difference. The average yield of the highest number of salable leaves on siomak plants was in the combined treatment of 100 ml lamtoro leaf POC dose with 6 times the frequency of lamtoro leaf organic fertilizer, which was 18.00 strands.

The combination treatment that produces the smallest average number of salable leaves on siomak plants is the combination treatment of 50 ml/plant of lamtoro leaf liquid organic fertilizer (POC) with 4 times the frequency of lamtoro leaf organic fertilizer application.

So that the combination treatment that can increase the average number of marketable leaves on siomak plants (Table 4.) is the combination treatment of 100 ml lamtoro leaf liquid organic fertilizer (POC) with a frequency of 6 times lamtoro leaf organic fertilizer.

Table 4. Average Number of Marketable Leaves of Siomak Plants in the Combination Treatment of lamtoro leaf POC doses and the frequency of lamtoro leaf organic fertilizer application

Note: Numbers followed by the same letter in the same column and row are not significantly different based on the 5% BNJ test.

The results of the treatment of various doses and frequencies of POC Lamtoro leaves based on analysis of variance had a significant effect on vegetative parameters including plant length, leaf area and number of leaves. In general, from each of these growth variables, the dose of liquid organic fertilizer (POC) of 100 ml of lamtoro leaves/plant with a frequency of 6 times of giving lamtoro leaf POC gave higher yields. Meanwhile, the dose of liquid organic fertilizer (POC) for lamtoro leaves of 50 ml/plant with the frequency of giving organic fertilizer for lamtoro leaves 4 times gave the lowest results.

The treatment factor of the combination dose of lamtoro leaf liquid organic fertilizer (POC) and the frequency of lamtoro leaf POC administration had a significant interaction with siomak plant length at the age of 21-60 HST. This is in accordance with research (Odang and Aep, 2019) [3] namely the addition of POC lamtoro leaves has a real effect on increasing the height of pakcoy plants. The highest average yield of siomak plant length aged 56 and 60 HST was in the combined treatment of 100 ml lamtoro leaf liquid organic fertilizer (POC) and the frequency of fertilizer application 5 times. Adding organic matter can increase the growth of ground kale plants. The fertilizer used is liquid organic fertilizer made from lamtoro leaves [4]. The results of research are similar to Ratrinia, Maruf and Dewi. (2014) [5] lamtoro leaves contain relatively high nitrogen nutrients so they are able to provide the nutrients needed by plants.

The treatment factor of the combination of doses of lamtoro leaf liquid organic fertilizer (POC) and the frequency of lamtoro leaf POC administration had a significant interaction with the number of siomak plant leaves at the age of 49, 56 and 60 HST. From these results it means that the higher the dose of liquid organic fertilizer and the more the frequency of liquid organic fertilizer application, the better the number of leaves results because the nutrients needed by plants are fulfilled.

The results of the analysis of variance showed that the combination treatment of lamtoro leaf POC doses and the frequency of lamtoro leaf POC administration showed a very significant difference in leaf area. Plants with wider leaf area resulted from treatment with POC administration than treatment without POC [6]. Oviyanti, Syarifah and Hidayah's research results. (2016) [7] showed results that giving mustard plants more POC levels could stimulate cell metabolism that occurs in the marystematic tissue at the point of leaf growth so as to increase the yield of leaf area.

Based on the analysis of the POC content, it showed that the POC results from the study contained 0.07% N-total macro nutrients, 0.01% P-total, and 0.12% K-total. This result is not too different from Jeksen and Mutiara (2017) which shows that the POC of lamtoro leaves has a total N content of 0.068%, P 0.029%, and K 0.158%.

The results of the analysis of variance in this study showed that the treatment of various doses and application frequencies of lamtoro leaf POC had a very significant effect on the yield components including the number of marketable leaves and the wet weight of siomak plants. The average yield of wet weight of siomak plants and the highest number of salable leaves on siomak plants was the combination treatment of 100 ml lamtoro leaf POC dose with 6 times the frequency of giving lamtoro leaf organic fertilizer.

The application of larger POC doses and more frequency gave higher plant wet weight results than the treatment without the addition of POC and the treatment with lower POC doses and fewer frequencies. In Syofia's research, Munar and Sofyan (2014) [8] stated that giving more POC would lead to an increase in crop yields. The growth component will affect the yield component of a plant. Plant wet weight is affected by leaf area per plant, plant height, and stem diameter per plant. The greater the value of leaf area per plant, plant height, and stem diameter per plant, the greater the wet weight of the plants produced. An increase in the wet weight of siomak plants can occur because plants with a large number of leaves can produce more nutrients.

An analysis of the chlorophyll content of the leaves at the treatment dose and frequency of POC showed that the treatment without POC (control) with 1.3 g urea at a frequency of 6 times POC administration obtained a total chlorophyll of 45.20 mg/L and a treatment dose of 100 ml POC and a frequency of 6 times POC administration obtained a total chlorophyll of 44.11 mg/L. These results indicate that the amount of chlorophyll with a treatment dose of 100 ml and a frequency of 6 times administration has results that are not much different from the control treatment, this means that with POC lamtoro leaves can give good results and are also not significantly different from the control treatment which uses inorganic fertilizers.

The results of Wasonowati's research (2009) [9] stated that if the nitrogen element is sufficient, the leaves will be very green than those that lack nitrogen elements and the photosynthesis process runs more smoothly. An increase in the rate of photosynthesis can produce carbohydrates in greater quantities.

The combined treatment of lamtoro leaf liquid organic fertilizer (POC) doses and the frequency of lamtoro leaf organic fertilizer application had a significant effect on the vegetative parameters of leaf number, leaf area, plant length, and on the generative parameters of siomak plant wet weight, and the number of marketable leaves. The combination treatment of liquid organic fertilizer (POC) doses of 100 ml of lamtoro leaves/plant with a frequency of 6 times of lamtoro leaf POC is the most efficient because it gives good results to siomak plants.

Conflict of Interest:

The authors declare that they have no conflict of interest.

Funding: No funding sources 

Ethical approval: The study was approved by the Institutional Ethics Committee of Universitas Negeri Makassar

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